Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
The present invention relates to the application
of thyristor chopper apparatus for determining the propul-
sion power and electric brake operations of a transit vehiclehaving series propulsion motors, and more particularly to
control apparatus including a microprocessor that is pro-
grammed for the desired control of such thyristor chopper
apparatus.
Direct current power has been supplied to the
series propulsion motors of a transit vehicle with a thyris-
tor chopper, such as disclosed in U.S. Patent 3,530,503
issued December 22, 1970 to H. C. Appelo et al, for con-
trolling the acceleration and speed of the vehicle by turning
the propulsion motor current ON and OFF in a predetermined
pattern. The thyristor chopper can provide either regenera-
tive braking or dynamic braking when braking is desired.
In an article entitled Automatic Train Control
Concepts Are Implemented By Modern Equipment published in
the Westinghouse Engineer for September 1972 at pages 145 to
151, and in an article entitled "Propulsion Control For
Passenger Trains Provides High Speed Service" published in
the Westinghouse Engineer for September 1970 at pages 143 to
149, there is described the operation of the P signal for
-- 2 --
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:, ` ~ , ' : ` ' ,' , ' " .` ' ` ,. .. " ',,: i-' ' ' - / :' '' ,~, ' .
'. ' ' :. . ' ` i - ,- . . : :. , , : `'` i ~. ,
~ 46,456
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controlling all powered vehicles in a train to contribute
the same amount of propulsion or braking effort.
In an article entitled Alternative Systems For
Rapid Transit Propulsion And Electrical Braking, published ~ -
in the Westinghouse Engineer for March, 1973, at pages 34-
41, there is described a thyristor chopper control system
for propulsion and electrical braking of transit vehicles.
The thyristor chopper provides a propulsion system that is
superior in smoothness and ease of maintaining a given
speed, which latter feature is desired for automatic train
control. Moreover, the thyristor system makes regenerative --~
braking practical because the response is fast enough to
continuously match regenerated voltage to line voltage, and
that matching prevents excursions in braking current and
torque due to sudden transients in line voltage. The reduc-
tion in power consumption that results from regeneratlve
braking can be significant, but another advantage is in
relation to minimizing heat input to tunnels otherwise
caused by dynamic braking.
The use of presently available microprocessor
devices, such as the Intel 8080 family of devices, is des-
cribed in a published article entitled "Mlcroprocessors -
Designers Gain New Freedom As Options Multiply" in Elec- -
tronics Magazine for April 15, 1976 at page 78 and in a
published article entitled "Is There A High-Level Lan~uage
In Your Microcomputer's Future?" in EDN Magazine for May 20,
1976 at page 62. -
SUMMARY OF THE INVENTION
An effort control apparatus and method are pro-
vided for an electric motor, such as a direct current seriçs
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propulsion motor used with translt vehicles, through the
operation of an effort control parameter RE which influences
the armature current of the motor in relation to one or more
operational conditions such as a drop in the power supply
line voltage, the supply line current is greater than a
predetermined limit or reference value, the load weighed
current request becomes greater than the supply line voltage -
and the supply line voltage becomes greater than any one or
more of a provided plurality of successively larger prede-
termined limits or reference values. The effort control
parameter is provided with a minimum value limit and a
maximum value limit.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a functional showing of the present
control apparatus in relation to the input signals and the
output signals operative with the control apparatus; .;}
Figure 2 illustrates the input signal operation~
and the output signal operations of the present control '
apparatus; :
Figures 3A and 3B illustrate schematically the
provided interface of the present control apparatus;
Figures 4A and 4B illustrate schematically the
provided interface between the present control apparatus and
the controlled transit vehicle;
Figure 5 illustrates a prior art chopper logic
control apparatus;
Figure 6 illustrates schematically a prior art
motor operation control apparatus;
Figure 7 illustrates schematically a prior art
motoring mode of operation of the motor operation control
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apparatus of Figure 6;
Figure 8 illustrates schematically a prior art
braking mode of operation of the motor operation control
apparatus of Figure 6,
Figure 9 illustrates schematically a prior art
chopper apparatus;
Figure 10 illustrates the coding of the program
listing included in the appendix;
Figure ll shows a performance chart for a first
actual operation of the present control apparatus with a two
vehicle train and one vehicle not powered, for a normal
power run without regenerative braking;
Figure 12 shows a performance chart for a second
actual operation of the present control apparatus with two
vehicles when both vehicles are working together in power
and in brake, for a fully receptive power supply line;
Figure 13 shows a performance chart for a third
actual operation of the present control apparatus with two
vehicles working together in power and in brake, for a par- `~
tially receptive power supply line;
Figure 14 shows a well known operational charac-
teristic curve for a typical series propulsion motor opera-
tive with a train vehicle and the present control apparatus;
Figure 15 shows the prior art response of a pro-
pulsion motor control apparatus to a P signal; and
Figure 16 illustrates the commutative capability
of the typical chopper apparatus.
DESCRIPTION OF A PREFERRED EMBODIMENT
In Figure 1 there is shown a functional illustra- :
3q tion of the present control apparatus in relation to the
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input signals and the output signals operative therewith,
and including a CPU microprocessor 94 operative with a PROM
programmable memory 96 and a scratch pad RAM random access
memory 98 used for intermediate storage. The application ~ -
program, in accordance with the program listing included in
the Appendix, is stored in the programmable memory 96. The
microprocessor 94 can be an INTEL 8080, the random access
memory 98 can be an INTEL 8101, and the programmable memory
96 can be an INTEL 1702 programmable read only memory, which
items are currently available in the open marketplace.
There are four illustrated categories of input and output
signals relative to the controlled process operation o~ a
transit vehicle. The digital input signals are supplied
through digital input 100 from the transit vehicle and
include the slip slide signal SLIP, the thyristor tempera-
ture sensor thermal overload signal THOUL, the effective
value of the line filter capacitor as indicated by the fuse
counter signal FUSE, the power circuit condition indication
signal LCOC, the power and brake feedback signal BFEED, the
field shunt feedback signal FS, the brake status signal BRKI
and the clock signal 218 Hz. The analog input signals are
supplied through analog input 102 and include the first pro-
pulsion motor leg current Il, the second propulsion motor
leg current I2, the line current IL, the line voltage LV,
the primary power request or brake request control signal P,
the air pressure in the vehicle support bag members provid-
ing load weighed current request slgnal IRW, the analog
phase slgnal IP and the vehicle actual speed signal Sl. The
dlgital output signals are supplied through digital output
104 to the controlled transit vehicle and include the line
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switch control signal LS, the power brake mode control
signal P/B, the field shunt control signal FS, the first
braking resistor control signal BCl, the second braking -
resistor control signal BC2, the third braking resistor
control signal BC3, the zero ohm field shunt control signal ;~
BDC, the 10 kilometer per hour signal 10 KPH, the 25 kil-
ometer per hour signal 25 KPH, the phase zero control signal
0O, the rate timing signal BOOST, the ON suppress control
signal SUPP and the zero speed signal ZS. The analog output .
current request signal I+ is supplied through analog output
106 going to an analog phase controller 108 operative to , ;~
supply the control signal ON to fire the chopper thyristor
Tl, the control signal OFF to fire the commutating chopper .
thyristor T2, the control signal T5 for the T5 thyristor in
the propulsion motor control chopper apparatus and the -.
analog phase indication signal IP going to analog input 102.
The time period associated with turning the chopper ON and
OFF is at a constant frequency of 218 Hz, that defines the
clock time interval for the program cycle and for checking
20 the process operation. During each of the 218 time inter- :
vals per second, the program cycle operates through the
application program. It was necessary in the prior art for
some of the input signals to be filtered to slow down the ~;
effects of noise transients and the like, but the computer :
program now samples the input signals 218 times every sec-
ond, so if desired each signal can be checked during each
program cycle and, if the signal stays the same as it was
before, the proper response can be provided. By sampl~ng
all the input signals every program cycle and by addressing
every output signal every program cycle, if noise transients
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are received, their effect can be minimized or eliminated.
For the output signals, a correct output can be given 5
milliseconds later and faster than the power response time
of a train vehicle. For the input signals, digital filter-
ing by comparison with old data can eliminate transient
effects.
The train control system operative with each
vehicle provides a P signal which selects a desired propul-
sion effort and this signal, as will be described in rela-
tion to Figure 15, goes from 0 to 100 milliamps and estab-
lishes how much propulsion power or braking effort is desired ;
by a particular train vehicle. The P signal is decoded to
determine the proper motor current to generate the proper
effort. In addition, there is a confirming signal, called
the BRKI signal which determines when propulsion power and
when braking effort is applied. The purpose of the BRKI
signal i5 to control the power switching at the correct time
to avoid one car braking while another car is in propulsion.
Contact closures in the power circuitry are detected to
establish that the power contacts have been made up properly
and to read~ust the settings in the logic. For instance, in
field shunt operation, the amount of motor current is ad-
~usted to keep from getting an undesired physical ~erk of
the vehicle. A failsafe reading of the P signal level is
made such that, should the P signal be lost, the train
Gontrol automatically goes into a brake mode. The present
propulsion control apparatus determines which switches to
close and when to close them to modify the power circult
properly. A dynamic brake feedback signal is sent to the
mechanical brake control for providing the blending of
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~C970375
mechanical brake necessary to maintain the deceleration
level required by the P signal. The P signal is in reality
a vehicle acceleration or deceleration request.
The propulsion control apparatus provides output
pulses to the main power thyristors to tell them when to
turn ON and when to turn OFF. When a command signal is
sensed, for example, if the vehicle is in propulsion or
power mode and the command signal desires the vehicle to
brake, the control apparatus senses any di~ference between
the desired motor current and the actual motor current and ~ ;
ramps down the actual current as required. When the current ;~
gets down to a desired level, the control apparatus opens
all the propulsion switches and reconnects for a brake
operatlon, then ramps the motor current back up again to the -
level established by the desired brake operation.
In Figure 2 there is illustrated the input signal
operations and the output signal operatlons of the present
control apparatus, including the microprocessor 94 operative
with its random access memory 98 and its programmable memory
96. The analog input signals are supplied through the
analog input 102, through the multiplexer 120 and analog-to-
digital converter 122 and input port 124 of the micropro-
ce~sor 94 operative with a data bus 126 and address bus 128.
The address bus 128 and data bus 126 are operative through
an output port 130 to control the multiplexer 120 and the
analog-to-digital converter 122. The dlgital input signals
are supplied through the digital input 100 operating through
buffer 132 with the input port 136 operative with the data
bus 126 and the address bus 128. The digital output signals
are supplied through digital output 104 including output
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ports 140 and 142 and respective isolation circuits 144 and
146 with drivers 148 and 150 in relation to the data bus 126
and the address bus 128. The analog output 106 is operative
through output ports 152 and 154 through a buffer 156 and a
digital-to-analog converter 158 with the analog phase con-
troller 108.
The central processor 94 addresses a particular
input port or output port or memory location and then trans-
mits data to or receives data from that location on the data -
bus 126. For example, the central processor 94 can address
an input port, such as input port 124 for the analog-to~
digital converter 122 and the multiplexer 120. First it
presents data to output 130 to tell the multiplexer 120
which analog circuit input signal is desired. Each analog
signal has some sort of buffering, such as a differential
amplifier or a low pass filter. When the particular input
ls addressed, the analog-to-digital converter 122 cycles for
converting that data. The digital feedback signals from the
digital feedback 100 come in and can be read whenever de-
sired. A monitor or display panel 192 can be provided to
indicate the state of operation of the central processor 94.
The output port 153 is operative through digital-to-analog
converter and buffer amplifier 194 with the provided test
point 190 and is operative with display 192. The manual
switches 196 are operative with input port 137 as shown.
The P signal goes through the multiplexer 120 to `
request a particular vehicle operation. The control pro-
cessor 94 senses the various currents, the various voltages
and the vehicle speed. It takes digital feedback signals
through buffers to know what is going on in the power
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circuit in relation to currents and voltages. The control
processor 94 provides output command signals to the power
circuit. Command signals go on the data bus and output
ports function as latches so the control processor 94 can
proceed to do other things while each latch remembers what
is on the data bus at a given address. The control pro-
cessor 94 outputs a signal to close whatever power switches
are desired and also outputs a requested motor current. The
requested motor current is decoded in a digital-to-analog
converter. The analog motor control circuit, in response to
this current request, senses the actual motor current and
the commutating capacitor voltage, and if everything is
satisfactory, the motor control circuit appropriately fires
the drivers for the chopper apparatus.
In relation to effort versus motor current, at up
to about 100 amps, a typical series propulsion motor as
shown by Figure 14 provides little practical effort, and
above 100 amps the characteristic looks more or less like a `
straight line. As speed increases, there is wind resis-
tance, so the effective effort available is actually less in
power, and in braking, the reverse is true. When power is
requested, the motor current comes up to the level requested
by the P signal at a jerk limited rate. The vehicle in-
creases its speed because of the effort supplied. The phase
increases with speed, and when the phase approaches almost
100%, the full field operation is completed and the field
shunt is used to weaken the motor field, and this provides a
transient response problem; a very fast controller is
required, such that it can properly control the phase on the
thyristors. In actual practice, propulsion power is easier
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to control because in power a particular phase angle sets a
percentage of line volts on the motor, and this will give a -
~particular amount of motor current, such that if the phase
is set at 50%, a particular amount of current is provided in
power operation for a given speed. In brake operation, this
same relationship is not true since brake operation is more
unstable. If the phase is held at a desired place in power -~
operation, the motor current is stable; if a particular
phase setting is held in brake operation, the motor may go ;
to overload or to zero. If it is desired to initiate brake
operation, the control apparatus has to command brake which
ramps down the motor current on a ~erk limit, then opens up
the power switches and reconnects the power switches for
brake operation; thereafter, the control apparatus goes into
brake operation and ramps up the motor current to give the
torque necessary to get the desired brake effort. The motor
may be generating a considerable voltage that goes back lnto
the supply line so a resistor is put into the circuit to
dlssipate the excess voltage. As the vehicle comes down in
speed, the motor counter EMF drops and the chopper can no
longer sustain the motor current, so switches are operated
to change the resistors to maintain the desired motor cur-
rent. If the line voltage exceeds a particular value to
indicate that the line is not receptive and will not accept
the generated current, the motor current ls reduced lf no
dynamic braking resistor is used with dynamic resistors in
the circult, lf the line voltage becomes excesslve, the
motor current is shunted into the dynamic braking resistor.
In Figures 3A and 3B there is schematically lllus-
trated the provided interface of the present chopper logic
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control apparatus. The digital input lOO is shown in Flgure
3B operati~e through the buffers 132 with the input port
136. The analog input 102 is shown in Figure 3A operatlve
through multiplexer 120 and the analog to digital converter -i
122 with the input port 124 of the microprocessor. The
output port 130 is operative with the register 131 to con- ~
trol the multiplexer 120 and the analog to digital converter ~`
122. The output port 152 is shown in Figure 3A operative
with the digital to analog converter 158 and the analog ~
10 phase controller 108; the output port 106 is shown in Fig- -
.,~ .
ures 3A and 3B operative through buffer amplifiers 156 with
the drivers lO9, 111 and 113 for controlling the respective ~-
thyristors Tl, T2 and T5. The output port 142 is shown in
Figure 3B operative with the isolation amplifiers 146. The
output port 140 is shown in Figure 3B operative with the
isolation amplifiers 144. The output port 153 is shown in
Figure 3B operative with isolation amplifiers 194 and test -
point 190 and operative with display 192.
The pump circuit 151 operates to verify the proper
20 working of the present control apparatus including the ~
microprocessor 94 before the line switch is picked up and ! '.
the desired propulsion motor control operation takes place.
A dummy boost slgnal is initially put out at program line 16
to enable the line switch to be picked up, and during the
main program operation if something goes wrong the boost
signal disappears and the line switch drops out. The Y
shown in Figure 10 has added to it the boost bit, and then
time is called to wait as shown by the code sheet; the Y
carrier indicates whether the OFF suppress or the ON sup-
press is called for.
13-
. . .
. . . . . . . . . - . ~ ~ .
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1C970 375 -;r
The load weighed current request signal is output
by amplifier 153. Then the buffer 155 leads to the phase
controller amplifier 157, which takes the current request
signal from buffer 155 and the motor current signals Il and
I2 from lines 159 and 161. The output of controller ampli- -
fier 157 is the requested OFF pulse position or the phase
angle IP. The output of the amplifier 157 is compared by
comparator 163 with the timing ramp from amplifier 165 which
is reset by the computer each 218 Hz. The comparator 163
establishes when phase angle signal IP has exceeded the
timing ramp, and this would determine at the output of
comparator 163 where the OFF pulse is positioned. The logic
block 167 determines whether or not the OFF pulse positlon
output of comparator 163 is actually used. For example, if
comparator 169 determines there is too much current in the
system, the OFF pulse will be fired and might inhlbit or
suppress the ON pulse in logic block 171 which is operatlvç
w$th the ON pulse. The boost pulse comes ~rom the computer
and goes into the logic block 167 on line 173, and will fire
an OFF pulse on the leading edge if comparator 169 has not
already fired a pulse and suppress any further action out of
the control system. The logic block 167 ~ ncludes a flip-
flop operative such that if an OFF pulse is fired once
during a given program cycle, a second OFF pulse i5 not
fired during that same program cycle. The power up restart
cirouit 175 suppresses pulses until the control sy~tem has
time to operate properly. The circuit 177 is a monostable
to assure that only a pulse is output, and circuit ampllfier
111 drives the OFF pulse going to the gated pulse amplifier
for thyristor T2. In power mode the FET switch 179 is
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~ ~70375 .
closed to provide the desired motor characteristlcs com~
pensation slgnal, and in brake mode, this switch is opened
to provide a faster controller operation. The amplifier 181
checks the phase controller 157 to see if the slgnal IP ls
all the way up against the bottom stop to indicate too much
current, and if so, the circuit 171 suppresses the ON pulses;
this is used when starting up in power to skip ON pulses.
The ON pulses are suppressed by the power up circuit 183. ;:
. .
The ON pulses use the monostable 185 and the driver 109 a$ i~ ~`
10 in the operation for the OFF pulses. The safety enable ~ ;
signal or pump circuit 151 will stop the firing of an 0
pulse if repetitive boost signals are not provided. The FET
switch 187 energizes the line switch output, such that if
there is no activity on boost signal line 173, then the pump
circuit 151 will cause FET switch 187 to keep the line
switch dropped. The T5 signal comes from the computer to
flre the T5 thyristor, and monostable 189 drives the driver
circuit 1~1 going outside to the gated pulse amplifier for
the T5 thyristor. The phase controller 108 includes the
operational amplifier 157, with its attendant compensation
for power and brake operations. The computer can force the
controller 108 from output port 3-0 to zero for startup.
The pumping circuit 151 checks the activity of the computer
by looking at the boost line 173 for snubbing the provlsion
of ON pulses and thereby controls the line switch. If the
line switch is out, the propulsion and brake control system
cannot operate the chopper apparatus, so if something is `
wrong, it is important to snub the ON pulses quickly, be-
cause the line switch takes time to drop out, for this
reason an effort is made to stop the ON pulses when some
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1 [)70375
control apparatus malfunction occurs and is sensed by the
boost signals no longer being provided.
In Figures 4A and 4B there is schematically illus-
trated the provided interface of the present chopper lo~ic
control apparatus. In Figure 4A there is shown the micro-
processor 94 operative~with the data bus 126 and the address
bus 128 and the random access memory 98 and the programmable -
~memory 96. The output ports 153, 154, 152, 142 and 140 are
shown in Figure 4A. The input ports 124, 136 and 137 are
shown in Figure 4B, as well as the manual switches 196
operative with the input port 137.
In Figure 5 there is illustrated a prior art
chopper logic control apparatus including an analog computer
3ao operative with analog input signals provided through
analog input 302, with the tachometer signal passing through
a frequency to analog converter 303 before going to the
analog computer 300, with digital input signals provided
through digital input 304 passing through digital hard-wired
sequence logic 306, with the digital outputs passing through
the DC to AC predrive circuit 308 and the relay drivers 309.
The clock and pulse predrlve circuit 310 supplies the ON,
the OFF and the T5 control signals through the respective
gate pulse amplifiers 312, 314 and 316 for controlling the
respective thyristors in the chopper apparatus 318.
In Figure 6 there is shown a schematic illustra-
tion of a well-known prior art motor operation control
apparatus operative at the present time in Sao Paulo, Brazil,
as described in the above-referenced March 1973 published
article, with series propulsion motors and including a ,
thyristor chopper. A first pair of series motors 700 and
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702 and a second pair of series motors 704 and 706 are
energized in parallel from the third rail connection 708,
Figure 7 illustrates the well-known motoring mode
of operation of the motor operation control apparatus shown
in Figure 6. The chopper 800 is used to regulate the cur~
rent in the motor circuits. Turning the chopper 800 ON
builds up current in the motors 700, 702, 704 and 706 by
completing the circuit from the DC power supply positive 708
through the motors to ground. When the chopper 800 is -
turned OFF, the energy stored in the motor reactor 812 and
the inductance of the motors maintains current flow in the
motor circuit through the loop formed by the free-wheeling ;
diode 814. The average voltage applied to the motors is ~ ;-
controlled by ad~usting the ratio of chopper 800 OFF time to
ON time. This adjustment is made by the chopper control
logic to maintain the desired average motor current and the ,~
corresponding motor torque. When operating wlth full vol-
tage applied to the motors, the chopper 800 switches at the
normal frequency of approximately 218 Hz with an OFF inter-
val of about 6% of the total cycle time.
Figure 8 illustrates the well known braklng mode
of operation of the control apparatus shown in Figure 6,
where the motors 700, 702, 704 and 706 are reconnected by ; !
means of a power brake changeover PBC. The circuit is
arranged for regenerative or dynamic braking with the motor8
operating as self-excited generators. The fields 902, 904,
906 and 908 are cross-connected to force load divlsion
between the paralleled generators. In regenerative braking
the chopper ON and OFF ratio is regulated to maintain the
deslred current, with the more current providing the more
17
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braking. When the chopper 800 is turned ON, the current in
the motors increases. When the chopper 800 is turned OFF,
the current flowing in the chopper 800 is forced into the
line 708 through the free-wheeling diode 814 by the motor
reactor 812. The logic system for control of the chopper
800 during braking also monitors the voltage across the line
filter capacitor 910, and controls the chopper ON and OFF ~ ;~
ratio in such a manner as to prevent the capacitor 910
voltage from exceeding the line voltage 708, a condition -
that could result in increasing current during the chopper
OFF time and loss of braking control. If the capacitor 910
voltage during regeneration reaches a preset limit, the
logic removes regenerative braking by turning the chopper
800 OFF and keeping it OFF, with the remainder of the brak-
ing being achieved by friction brakes. The DC series motor
acts as a series generator and inherently has a maxlmum
generated voltage approximately twice the line voltage. To
provide for the maximum energy regeneration, resistors R2,
R3 and R4 are connected in series with the motors and the
line by the power brake changeover PBC. The IR drop across
the resistors opposes the generator voltage so that the
voltage across the capacitor 910 does not exceed the voltage
of supply line 708. As speed is reduced due to braking, khe
voltage o~ the series generators drops. When the ON and OFF
ratio of the chopper 800 reaches the point where the OFF
time is a minimum in order to maintain the motor current ak
the desired average value, the logic system triggers pickup
of one of the shorting contactors BCl, BC2 or BC3, which
reduces the IR drop in series with the generators in order
that the chopper 800 can continue to maintain substantially
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the same average braking current. The chopper 800 shifts
from a minimum OFF condition to a minimum ON condition
whenever a shorting contactor is picked up. In normal train
operation regeneration of power into the power supply some-
times is not possible because of a dead third rail, loss of
third rail power in the car or the absence of load being
taken from the third rail. In that event the circuit con-
sisting of thyristor T5 and resistor Rl provides almost
instantaneous shift from regeneration to dynamic braking.
The logic that controls the braking current makes the de-
cision at the time of each ON pulse as to whether T5 only ;-
will be turned ON or the chopper 800 also will be fired. If
the logic determines that the power supply is not receptlve
to regenerated energy, the chopper 800 is not turned ON and
only T5 is gated to divert the motor current through the
resistor Rl. At the time of the next fixed ON pulse the
logic again determines the need to fire the chopper 800 on
the basis of power supply 708 receptivity. Only when the
line 708 again becomes receptive will the chopper 800 be
gated and permit the voltage generated to rise to the point
where motor current again flows into the line 708.
In Figure 9 there ls illustrated a well known
chopper apparatus, with the chopper 800 being shown connec-
ted in the motoring mode. The first OFF pulse controls the
commutating thyristor T2 and the commutating capacitor Cc
charges to the same level as the line voltage; the capacitor
CC would charge to twice the line 708 voltage due to its
combination with the smoothing reactor L2 ~f it were not for
the free-wheeling diode 814. When the voltage on the capa-
citor Cc reaches line voltage level, the current through the
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capacitor Cc and thyristor T2 goes to zero and the thyristorT2 turns OFF. An ON pulse now occurs, simultaneously turn-
ing ON the main thyristor Tl and the reversing loop thyris-
tor T3. The load is then connected directly to the supply
voltage 708 causing the motor current to build up. Also the
voltage across the capacitor Cc beglns to decay as current
flows through the thyristor T3, the reversing loop reactor `
L3 and the thyristor Tl. The thyristor T3 turns OFF when
the current reaches zero and the voltage on the capacitor Cc
has reversed completely. Current is now flowing in the load
only and the circuit is ready for turn-off. Turn-off is
accomplished by turning the thyristor T2 ON. The load
çurrent now flows through the thyristor T2 and the capacitor
Cc. After a short delay due to the inductor L2, the thyris-
tor Tl turns OFF and the diode D4 conducts to help speed the
charging of the capacitor Cc. The reactor L4 limits the
rate of rise of current in the diode D4, and diode D4 stop~
conducting before the capacitor Cc charges to line voltage.
When the capacitor Cc is charged to line voltage, the free-
wheeling diode 814 conducts current and the thyristor T2turns OFF, leaving the circuit ready for another ON pulse
and the start of another cycle. The basic operation is the
same when the chopper is regulating current for motoring and
for braking.
The T5 pulse controls the operation of the T5
thyristor used in the brake mode to switch in the auxiliary
load resistor. When the power line is non-receptive to
regenerated current, the T5 thyristor is switched to lnlti-
ate dynamic braking. The braking resistors are shown as R2,
R3 and R4 in Figure 8, but there could be any number of
-20-
~- . 46,456
-
iO70375
series braking resistors provided, as desired. The zero ohm
field shunt in the braking mode can be operated when it is
desired to short the motor fields to try to kill all of the
field current and the residual magnetization of the field;
in the braking mode, the field may be shorted when desired
in an effort to collapse a magnetic field of the motor to
stop the car from electric braking when it is desired to
instead utilize the mechanical brake. The failsafe brake
effort is provided for energizing the vehicle mechanical
brakes and an analog control signal IP is provided for thi5 ~ -
purpose because of the fail safety requirement.
Figure 10 illustrates a code sheet that was used
to develop the program listing included in the Appendix. As
shown in Figure 10 and in reference to Figure 2, output port
1 (shown in Figure 2 as 153) was used for a test mode,
output port 3 (shown ln Figure 2 as 154) was used for analog ~ -
manipulation, output port 4 (shown in Figure 2 as 152) was
used for analog command signal output, output port 5 (~hown
in Figure 2 as 142) and output port 6 (shown in Figure 2 `~
20 divided into four bits each for 140 and 130) were used for
digital command signal outputs, input port 4 (shown ln
Figure 2 as 136) was used for digital input data, input port
5 (shown in Figure 2 as 124) was used for analog input data
and input port 6 (shown in Figure 2 as 137) was used for
test purposes in relation to manual input switches.
Figure 11 illustrates a performance chart for the
actual operation of the present control apparatus with the
propulsion motors of a train vehicle for a normal power run.
Curve 400 shows the speed of the vehicle in response to the
30 P signal shown in curve 402. The curve 404 shows the
-21-
--- 46,456
1~7(~375
resultin~ motor current and the curve 406 shows the re~ult~
ing line current. Curve 408 shows an individual first motor
circuit current sensed by a Hall current sensing device and
curve 410 shows a second individual motor circuit current
sensed by a Hall current sensing device. To illustrate that
the current increases at a predetermined rate with a slight
tilt to compensate for the losses in the motors, the abrupt
~9
step shown in the curves 404, 406, 408 and ~ illustrates
where the field shunt operation took place. When the P
signal drops, as shown by curve 402, the operation changes
from power to brake. The charts shown in Figure 11 are for
a power run operation of two train vehicles, where one car
was not powered and was pulled by the other powered car ln
an effort to lengthen the time response to see better what
was actually taking place.
In Figure 11, the top curve 400 is obtained as the
derivative of speed, with the second half actually going
negative. The bottom two curves 408 and 409 show the actual
outputs of the two sensors 750 and 752 shown in Figure 6.
The control operation is shown in the power mode, dragging
in ef~ect one car, and shows a field shunt change, whlch
changes the motor characteristics. When the vehicle starts
operating ln the motor mode the circuits are made up straight
through the switches 759 and 761 shown in Figure 6. When
the field shunt operates to change the motor characteris-
tics, the center switch 759 opens and the outer two switche~
763 and 765 are closed to put half the current through each
of the fields 760 and 762 in relation to motors 704 and 706
and the center switch 761 opens and the outer two switches
767 and 769 are closed to put half the current through each
- 22 -
-~ 46,456
107037.5 ~
of the fields 771 and 773 in relation to the motors 700 and '
702 to result in field weakening to change the motor charac- ~-
teristics. The microprocessor and the hall effect devices
750 and 752 combined with the high-speed analog controller
108 provides an improved control operation with less spikin~
action and this means the less prone the control is to
respond to an abnormal fault condition. Any increase in the
spiking action means a greater probability of blowing out ~ -
fusçs and the like and an increased possibility of sensing a
la false overload condition. There is energy wound up in thls
,: .
inductive circuit, and when there is a change in the motor
characteristics such as operation of the field shunt, the
motor current has to correspondingly change very rapidly.
In relation to the performance curves shown in -~
Figure 12, the two cars were operative with a receptive line
and both energized in power and in brake so they were work-
ing together in ef~ect as a single car operation. The ^ i
vehlcle speed shown by curve 420, initially increases for ;
acceleration and then decreases for deceleration in accord-
ance with the P signal shown by the curve 422. The line
çurrent I2 is shown by the curve 424 as the train speeds up
and then goes into the brake mode, the combined motor cur-
rent is shown by the curve 426 and the individual first
motor current Il by the curve 428 and the second motor
current I2 by the curve 430. When the P signal change~ from
power mode to brake mode, the spikes on the motor current
curve 426 correspond to the closing of the various braking
resistor switches.
Figure 13 illustrates performance charts for the ;
actual operation with a partially receptive supply line o~
~ ~:
~`~ 46,456
11970375
the present control apparatus with a two vehicle train.
These charts show the effects of trying to have a regener-
ation operation without the line being fully receptive. The
curve 440 shows the line voltage. This is an effort during
regeneration to put as much power back into the supply line
as can be practically accomplished, and this is done by
raising the line voltage up to a limit. The charts shown in
Figure 13 illustrate the superior per~ormance of the present
control apparatus including the microprocessor compared to
10 prior art type of control logic apparatus for the reason ;
that the computer program enables a better comparison of the
line voltage with the generated voltage and a better control
of cutting back the motor current each time the computer
pro~ram cycles, which current is cut back by changing the
ON-OFF ratio cycle of the chopper apparatus supplying thç
motor current. The prior art control apparatus cannot
function in this way in tha~ for each of the desired level~
of action, depending upon the level of voltage, a different
control circuit would be required.
In Figure 14 there is shown a motor characteristic
for a well-known series Westinghouse traction motor of Type
1463 operative through a 5.58 to 1 gear ratio with 30 inch
vehicle wheels.
In Figure 15 there is illustrated the well-known
response of the propulsion motor control apparatus to the P
signal 30. When the P signal 30 is below a value of about
60 milliamps, the control apparatus operates in the brake
mode and for a P signal above this value of 60 milliamps,
the control apparatus operates in the power mode.
In Figure 16 there is illustrated the commutative
-24-
~ ~6,456
1070375
capability of a typical chopper apparatus. From a minimum
level of about 10 amperes~ there i9 a substantially linear
characteristic relationship 61 between the line voltage and - ;
the commutation capability. ~he typlcal maximum requested
current 63 is such that there is an excess capability 65
above this maximum requested current le~Jel 63. In the pro-
gram line 134 the statement is made that anytime the current
request IRW exceeds the line voltage then increase the ~ ~
retard effort parameter R~ by two. At program line 14 if ;
the llne voltage is less than a determinea mlnimum ~alue,
then go back to the beginning of the program is another :
condition provided for the control operation, otherwise the
motors cannot obtain adequate current, there are commutation
problems and so forth. As shown in Figure ~ , it is desired
that the present control apparatus be operative with a line
voltage between 450 volts up to about 900 volts, and with a
current request below the determined maximum request level
63. As set forth in program line 134, the weighed current ~ ~*
request is kept below the line voltage to enable proper
commutation operation.
The program listing included in the Appendix i8
written in a language called PLM which was developed for use
with the INTEL microprocessor, such as the central processor
94. This is a hlgh level assembly language which can be
compiled lnto machine language. The numbers used in the
listing are in the hexadecimal number system, which is ~
base 16 number system. The first part of the listing in
lines 1 to 6 is for bookkeeping purposes and identifies for
the program the variables, the constants and the labels used
in the course of the program. More speclfically, K i~ an
-25-
~ 46,456
1~70375
artificial constant that is set in the brake mode ~or con-
trolling the brake buildup. IRW is the current request tha~
has been load weighed to compensate ~or the weight of the
car. I0 is the old current, Il is one of the motor circuit
currents and I2 is the other motor circuit current. IR ls
the current request. LVL is the modified line voltage. PR
is the permission to regenerate. RE is the retard the
effort due to a number of conditions such as overline voltage
or overcurrent or the like. TI is a timer. IL is line
current. L~ is line voltage. M is the mode of the external
equipment. M0 is the old mode and Ml is the transitory mode
as determined by the mode request and the position o~ the
power brake switch. N is a counter. PH is the phase that
the external analog controller is controlling and that ls
brought back in to establish the field shunting. PI is the
P signal that is used internally to do mode changes, PN 18
the new presently read P signal and P0 is the ~erk limited P
signal. TT is a timer. SI is the speed after the hyster-
esis has been applied. TOS is blank. ZI and Q are carriers
20 to the external analog controller and establishes certain ,
modes of operation. S is the currently read speed signal
and SS is the speed signal after it has been modified for
the taper on the power and brake modes. T is a timer, TP i8
a timer and TS is a timer. X, Xl, X2, Y and Z are external
controls ~or the analog controller. The three upper lines
ln the program listing are the variables used ln the pro-
gram. The next three lines are labels that identify in the
program certain starting points where the program can ~ump
to if needed. The compiler asSigns memory locations for ~;
each variable, and any time a given variable is read, the
-26-
.. . . . .. ... ~ - .
~ 46,456
11~7037S
computer knows the memory location. The mode labels are
used to assign locations in the program. `
The program defines tne desired sequence of s~eps
to be followed in controlling the propulsion and electric
braking operation of a transit vehicle. The safe mode of
operation is the brake mode. Therefore, the present control
program listing always starts up through the brake mode. If ~
an abnormal condition is detected, the program operation ~;
returns to the beginning and resequences through the brake --
mode. In comparison, the prior art control systems shu~ the
chopper OFF and did not try to reinitialize the equipment o~
to make sure the start of the operation was always ~rom the
same base.
In line 8 and mode 1 of the program an output port .
is dlrected to take a certain state, which is output port 1,
and the constant Q is init~alized to equal zero. In lines g ~ ~r
to 14 of mode 1 the program sets the output line swltch out
and checks i~ it is satisfactory and then reads the line
voltage. The program looks at the inputs, the slip slides,
and so forth to see that they are in proper form and then
tests for line voltage. If the llne voltage at line 14 is
not satisfactory, the program goes back to line 8 and the
start. If the line voltage is satisfactory, a false boost
signal is output at line 16 of the program because the line
switch cannot be picked up until a boost is provlded, so a
false boost is provided for this purpose. The motors will
not be energized at this time because the ON and OFF pulses
for the thyristors have been suppressed. If the line voltage
is all right, then in line 17 of mode 2 of the program the
line switch is closed for charging the commutating capacitor8
-27-
-` 46,456 `
107~375 ` `
and a check is made at line 18 to see i~ all the inputs are
as desired, and if they are satisfactory, the program at
lines 20 and 21 initializes certain timer variables.
In line 24 of mode 3 of the program the program
waits for a pulse ~rom an external clock at 218 Hz from a
crystal oscillator and when the program sees the rising edge
of the clock pulse, it provides the front end of the boost
to fire the ON pulse and puts the ON pulse positioner up to
output the request through output port 106 shown in Figure
3.
Lines 26 to 30 of mode 4 of the program are con-
trolling the external analog phase controller 108 to provlde
a boost interval ~or interpreting the current signals and
other things as to where the ON pulse will be and whether or
not it is allowed, and providing the ON suppress and the OFF
suppress. ,
In mode 5 lines 40 to 64, the program reads analog `
inputs and sets some variables. The P slgnal which is a
linear monotonic type signal is converted to effort. When
2~ the P signal is above 60 milliamps as shown in Figure 15,
this is a power request, when the P signal is below 60 ;-
mllllamps it ls a brake request, and below 20 milllamps it
is superbrake. I~ the line voltage LVL is less than some
predetermined number then the operator RE is set to retard
the effort. In addition, a speed taper is provided whereby
the speed aignal S is read in the outside world and is
modified SG that the internal speed signal SS stays at the - -
given level as long as the external speed signal is withln
predetermined limits. The external speed S is the actual
vehicle speed and the internal speed SS is the value that
-28-
1070375 46,456
the program is using t'or its operatlons. In e~fect a window
is p~t on the real vehicle speed and then used inside the
program as a bracketed speed such that as the outside speed
starts moving up, then the inside speed SS does not change
for as long as the outside speed S is within this provided
window, thereby if the outside speed S has noise inter~er-
ence, this provides a dead band for filtering the nolse and
other disturbances out of the actual speed signal S.
In lines 32 to 38 of mode 6, a determination is ;
made to go to power or go to brake and to confirm that the ;
control is in power or the control is in brake for the
purpose of setting up the request.
Starting at line 65 of mode 7, the P signal is
considered, which P signal has a value from 0 to 100, for
the generation o~ requested effort. If the control i9 in
power and the P signal is above 60 milliamps, thls requlres
more e~fort. If the P signal is below 60 milliamps and the
control is ln power, this maintains a minimum e~fort. If
the control is set in brake and the P signal is below 60
milliamps, this requests an increased brake effort down to
20 mllllamps, at which time the same ef~ort is held. If the
P signal is above 60 milliamps but the BRK signal does not
allow the control to go into power, a minimum brake effort
is maintained. In addition, a ~erk limit is provided ln
lines 75 to 82 of the program because the P signal can
change instantly to a full 100 milliamps and must be ~erk
limited such that the effort signal has to increase on a
ramp in one program cycle step at a time. The ~erk limited
P slgnal ls incremented by one unit each program cycle to
provide the desired ramp and repeatedly incrementlng one at
-29-
46,456
1~370375
a time determines how quick the effort increases. When
going into brake to prevent an abrupt fade-out of the
electric motors and to permit a smoother blending of the
friction brakes, a false fade-out is provided in lines 84 to
89 of the program so the electric braking fades out on a
softer slope to permit the friction brakes to maintain a
smooth and total braklng effort.
Lines 94 to 98 of mode 8 of the program provides a
check for a zero speed when the actual speed is less than a `
defined amount such that the vehicle is considered to be
standing still at zero speed. In addition, zero speed
clears the Z carrier within the program used in a situation ~ ,
when there is too much current in brake, which indicates an
overload and the operation should be shut down. In line 99
of the program, if the vehicle is at zero speed and a re-
~ quest for power is received, then the Z carrier is cleared
i to go back into power. A check is made at llne 100 to see ~.
if the llne voltage is too low, and if it is too low, the
program returns to the beginning of the program since there ;~
~o is not enough energy for the commutating capacitor and thepresent control apparatus is not requlred to operate below a ~`
predetermined voltage level, which could mean that the
vehicle is operating in a rail gap and the normal mode is to
; shut down the equipment when going into a rail gap. In
additlon in line 101 of mode 8, a check is made for exces-
sive line voltage which is used for incrementing the RE
request. If the voltage is too high, the Y carrier is set
~or the purpose of skipping ON pulses, and the RE request
starts reducing the motor current and this reduces the line
current. A check is made for LCOC whlch is a signal that
~ 3
,, ~ . .. . . " , ... . , .,,., ., . .,.. . .; ~ -
' 46,456
.
~70375 :
lndicates that all the power circultry is made up properly.
If any of the conditions, such as a thermal overload or a
slip/slide signal or the like, indicates improper action, ~-
the effort request is reduced and a suppression of the ON
pulse is effected. The Y carrier controls the ON pulse, the
OFF pulse and the T5 pulse. A check is made to see if motor ~ :
current Il is greater than motor current I2 or vice versa to
maintain the desired balance in the motors. A check is made
at line 105 to see that I0, which is a sum of Il and I2, i8
~0 not exceeding the request IR by more than a certain amount; ;
and if it is, the ON pulses are skipped.
The line current limit check in line 103 of mode 8 -
is provided to establish that the respective currents in ;~
each of the motor circuits are within a predetermined match ;~
of each other in relation to balance, if they are, the
operation is satisfactory; and if not, corrective action is
taken. Towing protection is provided in line 104 to enable ;
a train vehicle to be pulled or towed; if there is a failure
in the external equipment of a given vehicle, it i8 desired
that this be recognized and the vehicle operated such that
the other operating cars in the train can tow the disabled
vehlcle.
In lines 110 to 113 of mode 9 of the program the
current request is generated from the PR signal from which
the retard effort RE is subtracted to get the IR request
signal, and a speed tilt is provided in relation to a power
mode or brake mode of operation to change the current re-
quest IR on the field shunt and check of the inputs. The
effort request is the modified P signal which has been
modifled, then a speed tilt is added to the modl~ied P
31
,. . . . . ..
--~ 46,456
1(170375
signal by looking at the speed and tiltlng the P signal plus
when power operation is desired and tlltlng the P signal
negative for brake operation. The speed tilt is provided ~n
lines 114 and 115 by chopping off a little bik of the re-
quested current to compensate for the effort required to
maintain acceleration as speed increases; in effect, the
requested current is added to or subtracted from, depending
upon whether the control is in power or in brake, and this
adds or subtracts an increment o~ vehicle speed. In this
regard, during brake, the motor is dragging and the car is
dragging, so less effort is needed ~rom the motor current
because the drag is additive; however, ln power operation,
the drag is against the propulsion effort, so additional
motor current and effort is provided to compensate for the
needed extra power to properly operate the vehicle. The
~ provided speed tilt accomplishes this function in relatlon
'i to the speed of the vehicle. For the change of the current
request on field shunt in lines 116 to 118, if in field
shunt operation, then the motor characteristics are differ-
ent; the field shunt is field weakening, and there is a
different current level needed to get the desired motor
torque. The input check is provided at lines 120 to 123 to
make sure that all the switches and so ~orth are set where
they should be. The input 4 relates to the temperature o~
the semiconductors; this temperature in the prior art was
sqnsed and lf too high was previously used to shut every-
thing down as an irrevocable control move. In the present
system, restarting of the program is permitted after a too
high semiconductor temperature ls sensed. Input 4 is pre-
sently checked to see i~ the temperature is not too hlgh,
-32-
-- 46,456
~.0'70375
if it is satisfactory the ON pulse for the chopper ls :
allowed, and the incremental loop timer goes to mode 10. Ir
the semiconductor temperature is too high, the program goe8 ~ -*
to mode 10 and if necessary, a T5 pulse is fired; for a
given cycle of program operation, it may be desired to
cancel the ON pulse for that cycle or suppress the OFF pulse
or shut off the T5 pulse, or e~en to turn on the T5, depend- ~
ing on what is desired. If the semiconductor temperature i~ ;
the next cycle is back to a desired level, the program ;~
continues as normal to avoid a total shut-down and permit
the transit vehicle to continue running. The present control
provides a lessening of the provided effort to permit the
equipment to continue running within capabilities and con
tributing some partial desired e~fort to the traln movementt
Mode 10 of the program includes four selectable
control operations--namely, CYCPP which is confirmed power,
CYCBB which is confirmed brake, CYCBP which is cycling ~rom
brake to power, and CYCPB which is cycling from power to -
brake. These relate to differences in the desired vehicle
; 20 control as to when a particular control is desired and what
kind of control i5 desired. More specifically, ~or the
first control operation of CYCPP which is confirmed power,
it is desired to stay in power and to confirm that the
control is presently in power; the field shunt is closed in
lines 129 to 132 in relation to phase angle and the line
voltage i8 cut back in line 134 in relation to low voltage.
The close of the field shunt is provided to increase the
train speed. ~o keep the current flowing in the motor, it
is necessary to keep turning the chopper ON for longer
periods of time to keep increasing the percentage of voltage
-33-
46,456
~o~70375
to counte~act the counter EMF of the motor. At some control
point, lt is desired to move to field weakening, and the
control approach taken here senses the chopper being ON for ~
95% of the time and ~ield weakening is then provided. - -
In the second operation o~ CYCBB which is confirmed '~
brake, the request is to be in brake and the control opera_
tion is confirmed to be already in brake. This portion o~ ~
the program permits improved control in the braking mode in ~ -
relation to regeneration of power, wherein a sequence of
control steps is provided in lines 147 to 151 taking pro- Ix
gressively stronger action if the line voltage gets beyond ~
defined limits in an effort to control the maximum level of -
line voltage. If the line voltage starts gettling above a ;
~ predetermined first limit CE, then the request is cut bac~
¦ by two; if the line voltage gets above a predetermined
second limit D4, then the previous action has added to it a
stronger reduction and so forth through greater predeter-
mined limits to effect progressively increased current
reductions due to excess line volts by suppressing ON pul~es `
2a for the chopper to provide this current reduction.
A hysteresis for brake build-up is provided at
lines 152 to 156 by trying to get at least a minimum prede- I
termined current level in the brake mode after the motor
armature current has been reversed for braking; this portio~
; of the program provides the requested brake effort in co~-
~unction with a minimum effort to assure an ade~uate brake
current. The problem is to assure after the propulsion
motors are established in the proper way to start generatin~
brake current, that the armature current is built up in tlme
to prevent loss of the armature current because when chang.
-34-
,,, , ~ . :
- 46,456
:, ...i~.
~L070375
ing from power to electric braking, the braking armature r
current results from the residual magnetism left over ln the
field circuits of the motor. If the control apparatus does
not operate ~ast enough and lets this residual magnetism go
to zero, the armature current will not build up. In rela-
tion to a contribution to regenerative braking or electrical
braking, the present control apparatus enables a build up of ~-
; brake current after going to the brake mode, such that when
~ the build up contactor is closed thereafter only ON pulses ~
- 10 are provided with a defeat of OFF pulses until a minimum ~;
armature current is present in an effort to assure that the
armature current gets started as qui~kly as it can and ~;
before there occurs a loss of the residual field magnetlsm~
The propulsion motor is a series motor, so the armature and
fleld windings are in series. A~ter cutting the armature
current to go into a brake operation, it takes a whlle for
the field to be reenergized and this is the residual magne- --
tism that is involved in this operatlon; the armature circuit
is reversed for brake operation, but the field does not go
to zero lnstantly because of residual magnetism. When it 1~ -
~desired to go into the brake mode of operation, the program
maintains a minimum level of current in the brake mode and
permits the armature current build up in the opposite direc-
tion to an adequate level to maintain the field magnetism
and still reverse the current flow in the armature; the
control operation desires a current above a certaln value
and assures that at least thls value of armature current i8
maintained.
In the operation of the prior art analog system lf
something went wrong, one of the parallel operative analog
-35-
..
" . 46,456
~o70375
circuits was caused to reduce the effort request P signal to
maintain a reduced level for as long as necessary, and when
the system operation was again satisfactory the effort
request P signal would ramp up again on a ~erk limiter :.
basis, The previous analog control apparatus modified the P
signal in response to undesired line voltage and line cur~
rent conditions before the P signal was applied to control
the chopper apparatus. The previous analog control apparatus ; .:
did not have the capability of providing the time variable :~
control operation as well as the high and low limits deter~
mined.
RETARD EFFORT PARAMETER
The retard effort parameter RE is a false parameter ~ `
that is used to modify the current request I+ output by the ~l~
analog output 106 to a level that i9 determiend by a number .
of operational conditions, and when RE is increased then a ;
bigger number is subtracted from the current request I+. ;
~he current request IR is determined primarily by the P ~;
slgnal coming into the analog input 102, and then the P
signal is modified in the program to develop the current
request I+. One of the factors which affects this is the
level of RE.
At line 76 of the program, a first condition is
established such that if the line voltage is less than a
determined value of oc8 hexadecimal, then there is subtracted
one unit quantity from RE everytime the computer program
goes through three cycles, such that N equals 3.
To increase RE at line 101 of the program, a
second condition is established that if the line current IL
is greater than a predetermined value corresponding to 0C7
-36-
_ 46,456
1070375
hexadecimal, then RE is increased by the quantity of plu8 2
every cycle through the program. This monitors the line
current IL, whlch is brought into the analog input 102, and
if IL goes above a certain predetermined maximum number,
then RE is increased. IL is the supply line current and it `
can be related in power by the sum of the two motor curren~s
Il plus I2 times the percentage of the ON time of the chop~
per, and in braking it is the sum of the two motor currents
Il plus I2 times the percentage of the OFF time. Line
current is measured physically in actual practice by moni-
toring the current in the supply line ~ith a Hall devlce.
At line 101 of the program, if line current IL exceeds a
certain predetermined amount, then RE is increased by a
factor of 2 every cycle of the program, and this is cumula-
tive. The purpose of this operation is to reduce the current
; request I~ because too much current is being drawn from the
line; there are control system considerations that desire a
llmit on the amount of power that a vehicle can draw from
the line.
At line 102 of the program, a third condition is
provided such that if RE is less than 2, then RE is set
equal to 2 to provide a boundary on the minimum value that
RE can have. For example in the operation of the statement
at line 76, i~ the line voltage were to remain continuously
less than this number OC8 hexadecimal, then RE would con-
tinuously be reduced by one for every three program cycle~
and it would go from a positive number and eventually become
negative, and RE should be stopped at a reasonable boundary.
The first portion of the statement in line 102 establlshes a
minimum quantity for RE equal to 2.
-37-
--~ 46,456
107~375
A fourth condition is provided by llne 102 in the
next portion, stating that if RE + 1 is greater than PR, ~ ;
which is related to the P signal, then RE is set equal to -~
PR - 1. What this says is that RE can never exceed the
current request by o~e. If RE, for some reason, keeps
growing bigger and bigger, and it is then subtracted from
the current request, the most that ls desired to be sub-
tracted is a value slightly less than the current request~
Therefore, RE is bounded by the relationship that it can
never be less than 2 and it can never be greater than one
less than the current request, with the current request
always being at least one. The first statement at line 76
operates every three program cycles on RE ln relation to
line current, and the next statement at line 102 establishes ;~
the upper and lower bounds of RE, and this is done every
cycle through the program.
PR is the current request that is determined by
the P signal; at line 111 of the program PR ls set equal to
P0, which is the ~erklimited and modified P signal. And
then at line 112 PR is set equal to PR + PR + PR + a con-
stant, which is a simple way of multiplication and setting
PR equal to three times itself plus a constant. At line 113
the current request IR, which is actually outputted from the
analog output 106 as the signal I+ in terms of the outside
world and is IR inside the computer, is set equal to PR
mlnus the parameter RE, and this signal IR then goes to ~he
analog phase controller 108 to control the chopper apparatus.
~ t line 134 of the program, if IRW is greater than
LVL then RE is set equal to RE+2. This statement provides
that lf the current request IRW, which has been load-welghed,
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~07~375 46,456
is greater than line voltage LVL whlch is a processed line
voltage, then RE is incremented by 2. The purpose of khis
statement is to modify the current request that is supplied
to the chopper, since the commutating circuit in the chopper
operates as a function of the line voltage. That is, as the
line voltage decreases, the energy storage elements in the
commutating circuit respond to the line voltage decreases
and the com~.utating capability of the chopper is decreased -
~as the energy stored in the commutative capacitor is de-
creased, so that the current request that is permitted isreduced as a function of the decreased line voltage, and
this is done once per cycle, by increasing the retard effort
RE as required for this purpose. ~ :~
At lines 147 to 151 of the program, there are a
number o~ conditions where the retard effort parameter is
modi~led in relation to measuring the llne voltage LV. In
line 147 if the line voltage LV is greater than a predeter-
mined value OCE hexadecimal, then RE is set equal to RE + 2.
In line 148, if the line voltage LV ls greater than a second
and larger predetermined value oD4 hexadecimal, then retard
effort RE ls set equal to the previous value of RE ~ 2 with
the addition of 3. In line 149, lf the llne voltage LV is
greater than a thlrd and stlll larger predetermlned value
ODA hexadeclmal, then retard effort RE ls set equal to the
prevlous value of RE + 2 ~ 3 with the addition of 4. In
llne 150, if the llne voltage LV ls greater than a fourth
and blgger predetermined value OEO hexadecimal, then retard
effort RE is set equal to the previous value RE + 2 + 3 ~ 4
wlth the addition of 5. And in line 151, if the line voltage
LV is greater than a fifth and still bigger predetermined
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~ ` 46,456
io70375
value OE6 hexadecimal, then a total suppression of ON pulses -~
to the chopper is provided by Y set equal to 02 hexadecimal.
This procedure is used to ad;ust the current request I+ to a -~
value such that the line voltage is regulated at a proper
reference point in the braking mode.
The operation of this is seen in Figure 13 in
terms of motor current as shown by curve 439 and line voltage,
as shown by curve 440 with the line voltage being increased
due to the switching of the braking resistors in the motor
circuit and the associated and resultant decrease in the
motor current which is caused by the effect of the retard
effort parameter RE being increased. The third curve 439
shows the slow reestablishment of motor current after each
such decrease and due to the operation of the first state-
ment in line 76 where the retard effort RE is reduced once
every third program cycle, to result in the decrementation
of RE at a slower rate than at which it was incremented.
A desired current request PO is established and
this control parameter RE modifies the desired current
request to determine the actual current request I+ that goes
to the analog phase controller 108. Line current modiflca-
tion of RE is a very slow process, since drastic action is
not desired in this regard, while line voltage is a very
quick process, and it is a progressive incrementation of RE
to make sure that the controlled operation does not exceed
the commutative ability of the chopper.
The retard effort parameter RE is responsive to
several input signals in the computer operation because the
several input signals are better correlated in a nonlinear
manner at one time. The line voltage will change in response
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,. . ,, .. .. . ~ ,...... .
`` 46,456
~L070375
to the current drawn by the train vehicle or in response to
the current supplied back into the line. If the line voltage
drops because too many vehicles are drawing current from the .
line, and if the individual vehicle system were uncontrolled
it would request still more current from the line, and this
would drop the line voltage still more. If the line voltage
is less than a predetermined value, such as oC8H, then the
retard effort RE is reduced by one unit every third cycle of
the program operation and this permits the retard effort RE
to recover to a minimum value as desired. As retard effort ;~
RE increases to put more of a current restriction on the
line supply, the requested effort is retarded and corres-
pondingly the line-supplied current is reduced, and this can
occur when the line voltage is getting too low for a glven
vehicle speed and tractive effort request. The retard
effort RE function is such that as the line voltage drops
for any reason, then the retard effort parameter RE is
lncreased to reduce the line-supplied current to a given
vehicle and the corresponding requested effort is retarded.
If the line voltage returns to a predetermined limit or
above, then retard e~fort RE has to be reduced toward zero.
If line volts are greater than some value such as 800 volts,
the retard effort RE is reduced for permltting the line-
supplled current to increase to the vehlcle as otherwlse
requested by the control system, and the retard effort RE 1
reduced at a ~erk llmited rate every third cycle of program
operation for providing a ramp effect.
The supply line current curve 424 of Figure 12
shows that as the vehicle speed is increased, the chopper is
phased ON more and more, and then using the relationship of
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.. . . .. . .... . .. . .. ... . ...... ..
. 46,456
1~7~375
the sum of the two motor currents times the chopper ON time
equals line current, there is shown the regulation of the
line current and the resultant leveling off and the regula-
tion action taking place and provided by the operation of
the parameter RE.
The retard effort parameter RE in its application
for ~he control of line voltage control in braking at pro-
gram lines 147 to 151 has four different levels of control
and each one of those acts as a different control operation
in relation to and also in a different time sense also.
Each time through the program loop a sample of line voltage
is taken to establish a value for RE. For each program
cycle the previous value of RE is changed according to the
value of the line voltage LV. Because the magnitude of line
voltage is not linear, it provides a different response time
with an accumulation or incrementation of RE, because the
operation is additive in relation to what RE was before,
until the RE reaches a level where the equation is satisfied.
