Note: Descriptions are shown in the official language in which they were submitted.
The present application i~ related l;o a pre-
viously f'iled and copendin~ Canadla~ pa~ent application
- Serial Mo~, 303,699 whieh wa~ fi~ed on M~y 1~, 197~ b~
F~ J~ P~nes et al and is erltitlad 'ITraction ~tor
Curr~nt Control Apparatus ~
BAC~ROUND OF T~E I~VENTION
~t is }cnown ~n th~ p~ior ark to c~ntrol ~he
cu~rent and volta~e, and t~us the speed and torque" o~
direct current propul~ion motors for a mass transit train
~ehicle using chopper appar~tu3 includlng ~olid ~ate
thyristors a~ con~rolled re~i~ier devices. An artlcle
e~itled "Alte~ate Systems for ~pid rran~it Propulsion
And ~lectricaï ~reaking~ th~ was published ~n ~he
- ~ ~or ~rch9 19739 a~ pages 34~41
describe~ ~he opera~ion o:E such c~o~er
~ ~. ~ S 3 ~ ' 1
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apparatus.
In an effort ~o reduce the noise interference w:Lth
wayside train control s:lgnalling ~yStem~, a b~o~,d b~nd ~o. l~e
spectra limitation may be desired for propulsion control
equipment on the train. The broad band nolse specLficatlon
typically will depict the peaks of each harmonic that exists
as a con-tinuous curve instead of the line spectra that
really exist such that the worst case chopper noise environ-
ment is thereby specified.
SUMMARY OF' TXE INVENTIO_
An improved multiple phase chopper apparatus is
provided for controlling the energization of a load such as
the one or more propulsion motors of a train vehicle, with a
reduced noise characteristic resulting from that chopper
apparatus. A train vehicle load operates in an environment
including operation control signals, such as speed control
signals, that require a minimum noise disturbance caused by
that chopper apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a single phase prior art chopper
apparatus;
Figure 2 shows a two phase prior art, chopper
apparatus including two chopper units;
Figure 3 shows the equivalent circuit f'or the
single phase chopper apparatus o~ Figure l;
Figure 4 shows the equivalent circuit for the two
phase chopper apparatus of Figure 2;
Figure 5 shows sig~al waYeforms to illustrate the
operation of the single phase chopper apparatus of Figure l;
Figure 6 shows current ~ave~orms to ilustrate the
--2--
S~54
1~7, 2~7
operakion of the two phase chopper apparatus of ~igure 2; t
Figure 7 shows the general waYeform of a typical
rectangular pulse provided in the output of a chopper appa~
r~tus;
Figure ~ shows current wave~orms ~or the two phas~
chopper apparatus o~ Figure 2, ~or the prior art l~0~ pha~
relationship operation
Figure 9 illustrate~ a chopper apparatus embodi-
ment of the present in~ention;
Figure 10 ~llustrates the conduction control
signal~ ~or the chopper apparatus of Figure 9 in accordance
with the present invention~ ~
Figura ll illustra~es a chopper apparatus o~ the
present invention connected to energi~ a common load;
Figurc 12 shows cu~rent waveforms for the two
phase chopper apparatus o~:Figure 1l, when operated in
: accordance with the present~inven~ion;
Figure 13 is a graph showing the enYelope of the
peak nolse spectra for a`tw~ phase chopper apparatus con-
trolled in a~1~0 phase relationship operation in accorfiance
with Pigure ~ as oompared to a two phase chopper apparatus
controlled wikh adjacent phase rela~ionship control pulses
in accordan~e with Figure 12; and
: Figure 14 (on the :same~ sheet as Pigure Il) shows a
suitable circuit arrangement ~or providing the control pulses
shown in Figure lO.
: ~ESCRIPT N N OF THE`PREFERRE~ ~MRODIMENT
In Figure 1 there is sho~n a prior a~ sîng1e
phase chopper apparatu~: operati~ ~ith a DC vo1tage source
lO and including a line resis~ance 12, a co~mu~ating inductor
14, a comm~ta~i~g~capacitor 16, Q commuta~ing resistor l~ a
~3~
P,5~3~
47, 287
main thyristor swltch device or controllable rect.l~ier 20, a
motor reactor 22, a load 24, illustrated to inc~ude ~ mo~or
armature 26 and a mo~or field 28, and ~ ~eewh~el.in~ diode
30. ~ conduction control apparatu~ 32 is opera~.iye ~o
provide control pulses to determine the ON conduc~ion period
of the th~ristor 20.
In Figure 2 there is shown a prior art two phase
chopper apparatus operative with the DC voltage source 10
and including the line resistor I2, the commutating inductor
14, t.he commutating capacitor 16 and the commutating resistor
18. The first chopper unit includes the main thyristor or
controllable rectlfier 20, the motor reactor 22 and the
freewheeling diode 30 operative with the load 24, whereas
the second chopper unit i~ncludes the main thyristor or
controllable rectifier 21~ the~motor reactor 23 and the
freèwheeling diode 31 operative with a load 25. Each of the
loads 24 and 25 are 111ustrated as a motor armature and a
series field winding, with the load 24 including the armature
26 and the field winding 28 and the load 25 including the
armature 27 and the field winding 29. The conduction control
apparatus 32 is operative to turn ON one of the chopper
units and when that one chopper unit has been commutated OFF
then to control the turn ON of the second chopper unit, and
when the second chopper unit has been commutated OFF to
control the turn ON of the first chopper unit, with this
operatlon being repeated as:desi~ed to determine the current
supplied to the respective loads 12 and 13.
~n Figure 3 there is sho~n the equiva~ent circuit
for the single phase chopper apparatus of Figure 1.
3 In ~igu~e 4 there is sho~n the equivalent circuit
--4--
.
. ~p;J~ ~ ~ 4
47,2g7
for the t~o phase chopper apparatus of Figure. 2.
~ n Flgu.re S ~here ~re sho~n the si~n~ Y5f~X~
to illustrate the operation of the pr~or art.single pha~e
chopper apparatU5 shown in ~igure 1. The ahoppe~ contro:l
signal shown in curve 5A determines the ON condition o~
operation, where the main thyristor 20 is conducting lvad
current, and the OFF condition Or operation~ where the main
thyristor 20 i.s not conducting load current and the freewheeling
; : : diode 30 provides load current during the OFF condition of
~ 10 operation of the main thyristor 20. The resulting load
: current sho~n in curve 5B passes through the load 24. The
: ~ current flow through the main thyristor 20 is shown in curve
5C:and the current~suppl~ed by the line including the DC
voltage source~lO is shown by ~the curve 5D.
In Figure 6:there are shown the current waveforms
to illustrate the~ o~perat~ion of the prior art two phase~:~
chopper apparatus~as~shown:in:Figure 2. The curve 6A~shows
the chopper current supplied by the first thyristor 20 and
: the curve 6B shows the ~current~ supplied by the second thyristor
20 device 21. The current:passing through the line filte~r,
including the resis'tor 12 and the inductance 14, is shown by
the curve 6C. The curve 6D shows the current supplied by
. . ~
the line including the~DC~voltage~source lO. It should be~
understood that the current control apparatus 32 prov1dès~ON:
control pulses to:the respective thyristor switches 20 and~
~: ~ 21, which control puls~es are 180V out of phase such that the
position of a current pulse of;~the first'thyristor~swi:te~h 20
is halfwa~ bçtween the current pulse~ provided.P~ the thyristor
switch devicç 21, as~sho~n b~ ~he respecti~e curves 6A and
~: 3Q. 6B, to in e:~fec't~pull pulses o~ current from the' 1lne that
: 5
~ ' . '
, '
: :
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.
,
are double the frequency o~ the ~N control pulses proYided
by the conduc~io~ contro~ apparatus 32 to each of the t~is~or
switch devices 2q:and 2I. This creates ],lne ~ol.se in rel~t~on
to the AC current flow ln the inductive branch of ~hiS pro- :
pulsion motor power supply circuit. ~hen the chopper appara~us
shown in Figure 2 is connected to ener~ize the propulsion
~ ~ motors of a train vehicle operating in a mass transit system,
: including train control signals in the track rails and which
~ train control signa}s have various~coded frequencies, it is
~: lO ~desired that the chopper~apparatus:shown in Figure 2 not:
interfere with t:hose traln control~signals and otherwise
: potentially result~in safety problems in relation to the :
operatlon of the train~vehicle.
In the normal~operation~of a chopper apparatus,
the thyristor switch~devices when~:closed switch the current
~ : into the load from the~line,:and;~when the thyristor swit:oh
is~open~the load~current~is~provlded through the operatlon
of~t:he freewheèling diode. :The filter, including the line:
resistor and llne~inductance, lsolates the line source from~ :
-: `20 the switching action going on inside the chopper apparatus;,
but the actual line~current has a lesser peak to peak ampli~
: tude because of~the~provided~filtering action. When the ;
; : chopper apparatus~is ~applying current to a large motor~
reactor, the induct~ance in the motor fields in effect ~draws
current from the line,:which~includes the filter consisting
of~the~line resistance,~the~line inductance and.the commutatlng~
: re~i~stor, assumi~ng that~the voltage~sourcè is a~zero impedance
sQurce~as~far as looking~t t:he ~C:characteristics are
concerned. It l.s known~ln~the~prior art that ~a two` phase : .
:30 chopper, such as sho~n~in Figures 2.and l~, shquld provide ~ .
~ ; -6- . : :
:~ ~ : :.
47,287
some reduction in the line noise. The prior art te~c~es
operating the two chopper un-Lts, of the t~o ph~se chQpper
apparatus shown in Figure 2, 180~ out of phase such that the
position of the current pulse in one chopper unit is hal~y
between the current pulses of the other chopper unlt, which
in effect pulls pulses of currents from the line ~ilker that
are double the frequency and can create the undesired line
noise in relation to the AC current flow in the inductive
branch of the circuit.
If it is assumed that the chopper apparatus operates
in a continuous current mode, such that if the thyristor
switch is ON, it is supplying motor currentS and if the
thyristor switch is OFF, then the freewheeling action will
maintain the load current until the thyristor switch is
turned ON again, then the equivaIent circuit arrangement
shown in Figures 3 and 4 can be made.
In Figure~7 there is illustrated the typical
rectangular waveform of a general rectangular pulse series
having an amplitude AB, having a pul~e repetition rate of
fBASE = l/T, where T is a time period between the leading
edges of the current pulses and the pulse width t = T/K,
where t is the width of a given current pulse and K = T/t.
A Fourier analysis can mathematically illustrate
the current pulse thàt the chopper apparatus is drawing from
the equivalent line filter circuit and permits calculating
the amplitude ILINE of the nth harmonic which, for a propulsion
motor control system normally run at 218 Hz, would be the
2Qth or 30th harmonic. The a~mpli~ude of this harmonic by
using these equations is a maximum for a 50~ 0~ duty cycle,
3Q and assu~ing ~he provided typical values for the line reactors
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.
in terms of inductance, ~esistance, line capacitor and
filter inductance, resistance and a t~pical load cur~ent,
when the impedance Or the inductive branc,h iS calculated,
this determines what the line current noise in the line is
by the ratio of -the two impedances times the harmonic cur~ent
amplitude. The calcultion for various n's provides a plot
of poin~s showing the peak noise current limit.
An = amplitude of harmonic n.
AB = amplitude of base current.
A A 2 Sin nR K = 2 A Sin nR - , for n = 1~2~ 3, 4 -- (1)
As stated above, the generated noise will be a line spectra,
so n will have integer values only. To calculate the amount
of noise current flowing in the line, the current is calculated
at each harmonic. This current is~then applied to the line
filter, whose attenuation at the harmonic frequency is
completed. The result is the noise spectra. Assume the
follo~ing typical values
Line reactor LL = 3 henry
RL = .0011 ohm
1ine cap CL = .014 farad
RC = 75 ohm
Base current AB - 1350 amps.
The impedance of the parallel resonant circuit can
be determined as
(RL2 t ~2 L2~ (R 2 ~ 1/w2 c2~ 1/2
tRL ~ Rc~ ~ (WL ~ C~ ~2~
:
and the impedance of the LR branch can be determined as
--8--
. . .. .
'~ ~" 7 J 5 ~
47,287
ZL = (R2L2 ~ ~2L2~ 1~2
ILIN~ ZL Qn (4~
The above mathematical calcula,tion determines the
amount of noise in the current pulses flowing in the track
rails.
Figure 8 shows the current waveforms ~or t,he two
phase chopper of Figure 2, operated with the ON control
pulses to the respective thyrlstor switch devices being
supplied in a 180 phase relationship. For example, the
curve 8A for a 10% ON condition of operation of the thyristor
switch 20 could illustrate the current flow through the ..
thyristor switch 20, with the cur~e 8B showing the current
: pulse ~low through the thyristor switch 21 for a 10~ ON duty
cycle of operation. The curve 8C could show the current
flow through the thyristor switch 20, with the curve 8D
.
showing the current flow through the thyristor switch 21,
for a 25% ON duty cycle of the chopper apparatus in relation
to energizing the propulsion motors represented by the loads
24 and 25. ~ :
In Figure 9, there is shown a two phase direct ~.'
current chopper apparatus connected for controlling the
: average current supplied from a direct current source 50 to -:
DC motor loads 52 and 54:, and a first chopper unit includes ; '
a s,eries mai.n thyristor switch deYice 5~ that repetitively
operates in an 0N condition and an OFF condition.to chop the ::
voltage appli.ed to the load 52. ~ second chopper unit
includes a series main thyristor switch device 58 that
repetitively~ operatés in an ON condition and an OFF condition '~
5B5~
47,287
to chop the voltage applied to the load 5LI. The control of
this voltage to earth load ls determined by changin~ the ~N
operation time in relation to the O~'F operation time o~ the
conduction by the main thyristors 3 ~or controlling the ~peed
B of the respective motor ~ loads 52 and 54. The speed of a
DC series field traction motor is proportional to the arma-
ture voltage and inversely proportional to the field current
or field flux in accordance with the relationship S propor-
tional to E/~. To reduce the speed of such a motor, the
armature voltage is decreased, and to increase the motor
speed the armature voltage is increased. The power supply
for a typical traction motor application can ke a relati.vely
constant direct current voltage source such as 900 volts
~rom a central power station. Each main thyristor switch 56
and 58 is gated to close and become conductive and subse-
quently commutated to open and blook as required to provide
an average voltage across the respective motors_52 and 54
which determines the motor speed. Each of the chopper units
shown in Figure 9 operates in accordance with the disclosure
of the above referenced related patent application, the
disclosure of which is incorporated herein by reference.
Each of the main thyristor switches 56 and 58
requires a commutation circuit to become blocked when it is
desired that the main thyristor switch no longer conduct
current to the motor. A commutation circuIt for th~ main
thyristor switch 56 is shawn to include a parallel connected
com~utating capacitor 6Q and a commutating thyristor switch
62 operatiYe to shunt the m~tor current and stop conduction
by the main thyristor switch 56. To block the main thyristor
3 switch 56 and st~op conduction ~of motor current b~v the main
-10- `
r~
1,7,287
thyristor switch 56, the commutating thyrlstor 62.is g~ted
by the conduction co~rol apparatus 32 ~o conduct ~d ~pplle~
a reverse bias voltage from the capaçitor 6~.across the maln
thyristor switch 56 to block the thyristor switch 56.
Similarly~ the capacitor 64 and commutating thyristor s~itch
66 operate to shunt the motor load current and stop conduction
of the motor current by the main thyristor switch 58. The
thyristor 66 is gated by the conduction control apparatus 32
to conduct and apply a reverse bias voltage from the capacitor
10 64 across the main thyristor switch 58 to block the thyristor
switch 5 8.
The conduction control apparatus 68 shown in
Figure 9 provides in accordance with the present invention
ON conduction control pulses to each of the main thyristor
switch devices 56 and 58 and provides OFF commutation control
pulses to each of the commutating thyristor switches 62 and :
66 as shown by the signal waveforms of Figure lQ. The
conduction control apparatus 68 provides an ON conduction
control pulse to the main thyristor switch device as shown
20 by the curve 80 to initiate the current conduction by the ~
main thyristor s~itch device 56 in accordance with the curve ::
82 showing the ON conduction time period of the thyristor
switch device 56. The conduction control apparatus 68 then
provides an OFF control pulse 84 to the commutating thyristor
switch device 62 for terminating the ON conduction time
period 82 Qf the main thyristor switch device 56. The
conduçtion control apparatus provides the~ON control pulse ~:
86 to the maln thyristor switçh device 58 to initiate the
current conduction by the main thyristor switch device 5~ as
3 shown by the curve~of the O~ conduction time period of the
:
~2~
1l7,287
main thyristor switch deYlce 58. The conduct~ con~rol
apparatus 68 then provides an OF~ cont~ol pulse ~ ~o ~he
commutating thyristor switch de~ice 66 ~or ~er~ln~ting khe
ON conduction time period of the main thyrls~or Swltch
device 58.
In Figure 11 the two phase chopper apparatus of
Figure 9 is shown connected to energize a common load, whlch
can include traction propulsion motors connected as shown at
page 36 in the above mentioned published article.
In Figure 12 there are shown current waveforms to
illustrate the operation of the two phase chopper apparatus
shown in Figure 11, when operated in accordance with the
teachings of the present invention. For a 10% ON duty cycle
condition of operation, the curve 12A shows the current flow
through the thyristor switch device 56 and the curve 12B
shows the current flow through the thyristor switch device
58, and the curve 12C represents the resulting current
supplied to the load 68. For a 25% ON duty cycle condition
of operation, the curve 12D shows the current flow through
2Q the thyristor switch device 56 and the curve 12E shows the
current flow through~the thyristor switch device 58, such
that the curve 12F represents the load current supplied to a
load device 68 by the chopper apparatus. For a 50% ON duty
cycle of operation, the curve 12G shows the current flo~
through the thyristor switch device 56 and the curve 12H
shows the current flow through device 58, such that the
curve 12I represents the load cu~rent supplied by the chopper
apparatus. For a 75~ ON duty cycle condition of ope~ation,
the curve 12J shol~s the current supplied by the thyr~stor
3a switch device 56, the curve 12K shows the curren~ supplied
-12-
~ 5~-~ 47,287
by the thyristor switch device 58, and the curve 12L sho~s
the current .supplied to the load 68 k~ the ch~ppe~ appa~rat
To reduce the AC nolse provided from ~h~e po~er
supply line, the respective chopper units ln the chop~er
apparatus are fired ON to become conductive by control
pulses arranged as shown in Figure 12 which are ad~acently
positioned. When supplying 1,300 amperes to energize a
propulsion motor, the chopper apparatus is already typically
built with multiple paths o~ components which may typically
include six main thyristor switch devices. These:can be
split up into multiple phase chopper units, without:adversely
changing the operating stresses on each individual component~
~ith some slightly additional wiring complexity and control
complexity. However, thls chopper~apparatus arrangement :~
will operate to reduce the noise and permit working with a
signal rail system having longer signaI block track rails
:
and longer runs between signal blocks. It is believed that
prior art propulsion motor controlling chopper apparatus
: will not be able to satis~y more restrictive speciflcations
in relation to noise limits that are permitted to be caused
by the line AC noise. This could necessitate a multiple
phase chopper apparatus arrangement as shown in Figures 9
and ll and controlled in the manner set forth in Figure 12
to reduce the noise lntroduced into the signal track rails
by the.propulsion motor po~er supply line. The chopper ~;
apparatus in accordance with the present inventlon pr.ovides
mult~ple chopper units as sho~n in Figures 9 and ll and
operated by adjacent contrQl slgnals, and can include ~
c~opper units ~here ~ is: a re~li.s~ic and practical number
3Q from .th.e: vie~point o~ cost and complexity.
~ -
~ 5~ Ll 7,287
In Figure 13 a graph is ~hown providln~ the
envelope of the peak nolse spectra ~or a two phase chopper
appara~us controlled by each Or the pr:Lor ar~ 18~ ou~ o~
phase relationship operatlon and the adJ~cen~ phase rel~tion
ship operation of the present inventi~n. The abscis$~,
represents the frequency times a thousand and the ordinate
represents the AC noise current in amperes, with the scale
being logrithmic. A typical more restrictive specification
for noise current above 5,000 cycles can be in the order of'
15 milliamps or less. The curve 13A shows ~he noise current
envelope ~or the prior art 180 out of phase conduction
operation as illustrated in ~igure 8. The curve 13~ shows
- the noise current envelope for the present adjacent con-
duction operation illustrated in Figure 12. With the prior
art chopper apparatus operatlon at 5,000 cycles, the noise
current is about 32 milliamps as shown by curve 13A. The
present chopper apparatus operation at 5,0Q0 cycles as shown
by curve 13B provides a noise current of about 15 or 16
milliamps.
As illustrated in ~igure 12, increasing the duty
cycle from 10% to 251 and then to 50% shows that at a 50% ON
duty cycle a continuous current is drawn from the line, with
substantially no AC line noise except ~or a small transient
overlap. If the duty cycle is then increased to 75% ON, the
same AC line noise is present as ~as present for a 25% ON
duty cycle. The normal operation of a propulsion motor
controlling chopper apparatuS is to start at a ~ery low duty
cycle and increase t~e du~y cycle as required to keeP ~he
current increasin~ as it is desired for the motor speed to
3Q increàse. ~t a 25% ON dut~ cycle, the maximum ~C line noise
14-
5 ~ 5'~
47~2~7
wlll occur because this pro~ldes the biggest amount of
ripple and then at 75% ON duty cycle a maximum noise condi~
tion again oocurs. A typical operatlon ~or propul~lo~ motor
chopper apparatus is at about a 50% ON duty cycle~ with mos~
of the running time being at this 50~ duty cycl~. The
curves in Figure 13 show the signi~icant improvement in
noise in~er~rence obtainable, with an improved noise factor
o~ two or more, with the propulsion motor chopper apparatus
being run with ad~ace~k control pulses as sho~m in Figure 12
In Figure 14 there i~ ~hown one suitable arrange-
ment that can be:~provided within the conduction control
apparatus 6~ to de~elop the conbrol pulses shown ~n Figure
10. The first ON pulse ~0 is pro~ided by a pulse source
100. This first ON pulse ~0 ~s fed into a DC flip-flop
deYice 102 which changes state in its output~ That output
i~ then fed into an opera~ional amplifier integrating de~ice
104 to result in a posltive going ~oltage change signal.
When the pulse ~4 is provided by the pulse source 100, the
flip-flop 102 will be reset and its output goes to zero.
The integrator 104 then s~arts a negative~goin~ voltage
change signal, a~d ~hen this voltage signal returns to zero
the operational ampli~ier 106 triggers a one-shot device 10
to generate the OFF eontrol pulse 90. ~n this wa~ the time
period between the control pulses ~O and ~ can be made to
e~ual the ti~ne per~od betwaen the co~rol ~ulses ~6 a~d 90.
The pulse source 100 ie responsive to the current
flowing in the:motor power equipment as well kno~ to persons ~-
skilled in this artO The ti~e period between the ON control
; pulse ~0 and the OFF control pulse ~4 is establ~shed ~or
15-
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regulating the cu~rent in the propulsion motor, such that a
desired average voltage i5 provided. A known reference
level is compared for adjustlng the deslred current leve~ in
the motor circuit.
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