Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to heat purnps and to
control sys-tems for polyphase motors, and, in particular, the
present invention relates to a heat pump suitable for use as an
automotive air condi-tioning unit and to a control system for
a polyphase mo-tor used to power -the heat pump.
In conven-tional automotive air conditioning systems,
' the compressor is driven directly from the motor vehicle engine
and thereforè the speed of the compressor is dependent directly
upon the speed of the motor vehicle engine. Accordingly
regulation of tempera-ture must be brought about by means other
than the speed of the compressor. However, in the present
invention, temperature regulation is brought about directly by
regulatiny the speed of the motor driving the compresso~. In'
the preferred embodiment relating to automotive air condition-
ing, a relatively low cos-t induction motor is used to drive
the compressor and a control system is provided which permits
the induction motor to be powered from the vehicle battery via
a control system which permits the speed of the induction
motor to be controlled and, hence, the temperature of the
lnterior of the motor vehicle.
According to one aspect of the present invention
there is disclosed a heat pump comprising an evaporator, a
' condenser, a pressure control device connected between the
outlet from said condenser and the inlet to said evaporator,
a compressor connected b'etween the outlet of said e~aporator
and the inlet to said condenser, an electr'ic motor arranged to
drive said compressor and a control system for said motor
arranyed to enable the speed o;E said motor to be controlled
as desired to adjust the amount of heat transferred from said
evaporator to said condenser in use.
,
~ ccordiny to another aspect of the present inVention
there is disclosed a control system for a polyphase motor
havinq one winding per phase and being eneryised from a DC
supply, said control system comprising a pair of electrically
operable switches for each phase of said motorr one switch of
each pair being operative to connect the correspondin~ windiny
of said motor to one terminal oE said DC supply and the other
switch of each pair being operative to connect said correspond-
ing winding to the other terminal of said DC supply; se~uenciny
means connected to said switches to operate the switches of
each pair alternatively and to simultaneously ope;rate one
switch of every pair in sequence; and rate means connected to
said sequencing means to control the rate o~ operation of said
.
sequencing means whereby the rate of oneratio,n of said se~uencin-
means controls the speed of operation of said polyphase motor,
One embodiment of the ~resent invention will now be
described with reference to the drawings in ~hich
Fig, 1 is a diagrammatic perspective view of a heat
pump system according to the invention;
Fig. 2 is a cross-sectional diagrammatic view of the
sealed unit used in the heat pump shown in Fig. l;
Fig. 3 is an e~ploded perspective vie~ of the com-
ponents of the motor and pump lncorporated within the sealed
unit shown in Figure 2;
Figs. ~A - ~H are sequential cross-sectional views of
the imneller section of the pump shown in Fig~ 3 at different
stages in the pumping cycle.
Fiy. 5 is a block diayram of the preferred embodiment
of the control system;
30 , Fiy. 6 is a circuit diagram of the oscillator and 5
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volt logic power supply;
Fig. 7 is a circuit diagram of the master clock,
switch controls and phase sequencer,
Fig. 8 is a circuit diagram of the phase controller;
Fig. 9 is a circuit diagram of the main switch, and
Fig. 10 is a yraph of the phase voltages applied to
the induction motor as a function of time,
In the preferred form of the invention a heat pump is
constructed as an au-tomotive air-conditioning system although
it will be appreciated that the invention may be equally well
applied to a large number of heat pump applications.
Referring to Figure 1 the heat pump comprises a con-
denser 101 which would normally be mounted towards the front of
; the vehicle, and whlch may be assisted by a fan 102 to draw
cooling air through the condenser. An evaporator 103 is pro-
vided, mounted within the vehicle and fans or blowers 104 may
also be provided to force air through the evaporator 103 for
the cooling of the interior of the vehicle. The evaporator and
condenser are connected by a conduit 105 in which is incorpor-
ated two unidirectional refrigerant limiters 106 and a receiver-
drier 107. The refrigerant limiters act as expension valves,
each in con~unction with a non-return valve orientated in
opposite directions so that only one refrigerant li~iter is in
operation at any one time. In the preferred form of the invent-
ion the refrigerant limiters are in fact simple non-return
valves arranged to have a predetermined amount of"leakage" in
the normally closed direction. They therefore achieve substant-
; ially unrestricted flo~7 in one direction and restricted flo~
against a predeterm1ned resistance in the opposite direction
- 30 The air-conditioning unit is reversible as will be described
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hereinafter so that in use as a heat pump the oppositely
orientated refrigerant limiter comes into use to control the
pressure distribution in the system.
The evaporator 101 and condenser 103 are further
linked by a conduit 108 in which is mounted a compressor 109
driven by a motor 110. The motor is preferably provided in
` the form o~ an electric induction motor and the motor and com-
pressor are preferably sealed together as a sealed unit within
a casing 113. Electric power is supplied to the motor from an
automotive battery B14 by way of a controller 112 which will be
described in detail below.
When the system is used for cooling the interior of
the automobile, heat is pumped using a suitable working fluid
in the sy.stem, from the evaporator 103 to the condenser 101
where it is discharged to the atmosphere by the motion of
ambient air through the condenser assisted, if necessary, by
th~ fan 102. When it is desired to heat the interior of the
automobile, the motor 110 is reversed by suitable switching in
the control system 112, so that heat is then pumped from the
condenser 101 which now acts as an evaporator to the evaporator
103, now acting as a condenser. In this reverse cycle, the
oppositely orientated refrigerant limiter 106 comes into
operation to giye pressure control in the desired direction.
The use of two refrigerant lim;ters, with non-return valves,
acting as a by-pass, allows the refrigerant ~orking fluid to be
bi directionally controlled by the operation of the sealed unit
- comprising the compressor 109 and the motor 110. A dixect
curxent is supplied by the bat~ery B14 to the control unit 112
which conyerts the current to alternating current for use by
3Q the sealed unit induction motor 110, The motor 110 drives the
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compressor 109 in a direction which determines the function of
the heat exchangers 101 and 103 as either condensers or evap-
orators and the function of the refriyerant limiters 106 as
expansion or by-pass devices.
In the preferred form of the invention the motor 110
and the compressor 109 are sealed within a sealed case 113
(Figure 2). The only lines piercing the shell of the sealed
unit are the two connec-tions 114 and 115 to the evaporator and
the condenser and the electrical connections 116A to the con-
troller 112. In this manner the motor and purnp can both be
provided in an ideal working enviromnent which is beneficial
for lubrication of the bearings in the motor and the pump and
which keeps any dirt or foreign matter from becoming entrained
in the motor or pump which is particularly advantageous in an
automotive operating environment to ensure long life of the
working components. Furthermore by mounting the motor and
pump within a sealed casing it is possible to eliminate
individual bearing seals. This has the advantage of firstly
reducing the friction on the motor/pump shaft which therefore
allows the unit to operate at a higher efficiency and secondly
permitting the compressor to operate at higher speed than would
be possible with wiping seals, The sealed unit also oyercomes
problems of fluid loss from the system.
The compressor may be provided in any suitable form,
but is preferably provided in the form shown in Fi~ures 3 and
4A - 4H. In this configuration the pump or compressor takes
the form of an outer rotor 117 and an inner rotor 116 mounted
to rotate on a shaft 118 within a housing 119~ The inner
rotor, the outer rotor and the housing are all of substantially
the same thickness (apart from working clearancesl and are
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mounted be-tween end plates 120 and 121. The end plate 120
incorporates an inle-t port communicating with an inlet openiny
122 and the end plate 121 incorpora-tes an outlet port which
may communicate with an outlet openiny or in the case of the
two staye compressor in Fiyure 3, may communicate with the
inlet port of a further set of inner and outer rotors 123 and
I24 mounted within a housing 125 against a final end plate 126.
The end plate 126 incorporates an outlet port 127 in communi-
cation with an outlet aperture 128. The shaft 118 is mounted
at one end in a beariny 129 housed in the end plate 120 and
in a further bearing 130 mounted in a motor pump adaptor plate -~
131 and end plate 126 as will be described further below. The
end plates, housings and motor pump adaptor plates are fastened
toyether in asandwich-like manner, by mounting bolts 132
passing through holes 133 in each plate as shown. Each housing
plate 119 has an off-set circular aperture therein, in which
the outer rot~r 117 rotates. The inner rotor 116 has male
lobes 134 which mate with female lobes 135 in the outer rotor.
The operation of the compressor will now be described
with reference to Figures 4A - 4~1, which show in sequence the
stages during one complete rotation of the inner rotor of the
compressor. The outer rotor is provided with more female lobes
135 than the male lobes 134 of the inner rotor which may for
example have seven and six lobes respectively as shown in
Fiyure 3. In the form of compressor shown in Fic~s. 4A - 4H,
the inner rotor is shown with 4 male lobes and the outer rotor
with 5 female lobes for the sake of simplicity. In Fiyures
4A - 41-1 the inlet port is shown in broken outline at 136 and
the outlet port, also in broken outline~ at 137. These ports
are formed in the end plates 12Q and 121 resoectively. Durin~
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rotation of the compressor, because the outer rotor rotates
in a circular housing which is offset with respect to the
center of rotation of the shaft 118, one male lobe, for
example 138, of the inner rotor meshes with the corresponding
female lobe 139, whereas the opposite male lobe 140 passes
across the arcuate portion 141, between 2 female lobes 142 and
143. As -the inner and outer rotors are rotated by the shaft
118 from the position shown in Fig. 4A to the position in
Fig. 4B, the chamber 144 formed between the two rotors and
shown shaded in the diagram is increased in volume, while being
in communication with the inlet port 13~. This increase in
volume continues through the position shown in Figure 4C and
Figure 4D until, when the position shown in Figure 4D is
reached, the chamber 144 is no longer in communication with
the inlet port 136. As the rotation of the rotors continues
to thepositionshown in Figure 4E the chamber 144 comes into
communication with the outlet port 137, and the volume of the
- chamber decreases through the positions shown in Figure 4F and
Figure 4G. The ~orking fluid drawn into the ch~mber 144,
through the inlet port, by the expansion of the chamber between
the position shown in Figure 4~ and Figure 4D is then pressur-
ized by further rotation of the rotors so that the working
fluid is then forced out through the outlet port 137 between
the positions shown in Figure 4E and Figure 4G, By virtue of
the arcuate shapes between the male lobes of the inner rotor
and between the female lobes of the outer rotor there is rolling
line contact from lobe to lobe in the position shown in Fig.
4H. This contact effectively seals the inlet port from t~e
outlet port and prevents any leakage, It will be seen from
the relative ~otion of the dots 145 and 146 on the outer and
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inner rotors respectively, between the position shown in Fiyure
4A and the position in Figure 4H, that the outer rotor moves
more slowly according to the ratio of the lobes on the rotors.
The rotors also act as slide valves over the ports 136 and 137
and may be improved in their sealing efficiency by a suitable
coating such as a TEFLON (Registered Trade Mark) coating, over
the end plate surface~
The compressor may be constructed as a single stage
, compressor in the simple form, as shown in Figures 4A - 4H
or alternatively may be ganged as shown in Figure 3, where
there are two such rotors, sandwiched either side of an end
plate 121. This has the advantage that a compressor of any
desired capacity (,~ii,thin the design range) may be assembled
by simply adding further sets of components to give the
required number of stages to achieve the desired compression
ration. Manufacturing costs are thus kept to a minimum by
reducing the number of different components required. In the
form shown in Fig. 3, when viewed for clockwise rotation
the transfer port 147 in the end plate serves as the outlet
port for the rotors housed within the housing 119, and the in-
let port for the rotors within the housing 125. To achieve -~
the desired working relationship, the circular aperture in
the housing 119 is offset by 180 to the offset of the aperture
.
in the housing 125. The outlet port 127 in the end plate 126
then corresponds with the outlet port 137 as shown in Figures
4A - 4H. The inlet and outlet apertures 122 and 128 are
connected tothe conduits 114, 115 as shown in Figure 2.
It will be appreciated that although the compressor
has been sho~n as a single stage in Figues 4A - 4H and a double
stage in Figure 3, any number of stages may be provided to
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achieve the desired degree of compression simply by ganging or
sandwiching together further rotor components of the form shown
in Figure 3.
The compressor is provided with scavenge ports 148
protruding from the end plate 120 into the sealed area within
the casing 113. One of the scavenge ports is connected through
a non-return valve to the inlet port in the end plate 120 and
the other scavenge valve is connected through an oppositely
orientated non-return valve and through aligned apertures in
the end plates and housing to the final port in the end plate
126. These scavenye valves serve to maintain the sealed
pressure vessel 113 at reduced system pxessure, whether the
heat pump is heating or cooling and prevents excessive buildup
of lubricant within the pressure vessel. The scaVenge valves
also maintain the motor and compressor at a lower temperature
thus increasing efficiency.
It will be understood from a consideration of Figures
: 4A - 4H that the compressor will serve to pump working fluid
~ ' in the opposite direction, if the direction of ~otation of the
shaft 118 is reversed, and so the flow direction of the working
fluid is dependent upon the direction o,f rotation of the motor
110. Because two scavena,e valves 14~ are provided with.oppo-
sitely orient~ted non~return valves incorporated, there will
always be a scaven~e valve open between the lnside of the
pressuxe vessel and the inlet compressor port,
It will bé apparent that by simply switching the
direction of rotation of the motor 110, using the controller
switching 112, the direction of flow of working fluid between
the evaporator and the condenser may be reversed so that heat
ma~ be pumped from the heat exchange unit 101 to the unit 103
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or visa versa as selected. .The remainder of the circuit,
including the refrigerant limiters 106, is symm.etrical SQ that
the only change necessary to reverse the heat flow direction
is to change the direction of rotation of the compressor
The compressor is driven by an electric motor and
preferably by an induction motor comprising a motor frame 149
containing windin~s which connect to the power supply through
the connections 116. The motor frame is mounted to the motor
pump adapter plate 131~ A squirrel cage rotor 15Q is proyided,
mounted directly onto the integrated compressor drive-shaft
118 which rotates in the bea.rings 129 and 130, The inner rotors
116 and 123 are keyed to the shaft 118 by way of shaft keys
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In this manner a heat pump is proyided which. is
particularly suitable for automotive air conditioning and
heating in that po~er may be drawn from the direct current
power sup~ly of the vehicle and used to control in a simple
yet effective ~ashion, the hea-t trans~er o.~ the heat pump
~ unit. Because the motor drive is independent from the dri~e
from the engine of the automobile, it may be separ~tely
;~ mounted on:a part of the vehicle which is not prone to vibration
and which will therefore minimize fatigue failure in the
conduit line-108, The sealed motor compressor unit may also
be mounted on the yehicle in any convenient locationl which
will considerably simplify installation of air conditioning
within the vehicle ~ecause the system is si~ple and fully
reversible there is no need to provide a separate heating
system within the vehicle, which therefore considerably
reduces the cost of installation. The system is simple and
because the motor and compressor may be constructed as described
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and mounted together within a sealed casing 113, service
failure and maintenance should be kept to an absolute minimum.
The compressor characteristics can be desiyned specifically
for the optimum working speed range of the motor, so that a
high degree of efficiency and maximum utilization of the
current drawn from -the battery B14 may be obtained.
Because the motor and compressor are designed to
operate at a speed range in excess of 8,000 rpm, the size of
- the sealed unit containing the motor and the compressor is able
to be kept small and low in weight which leads to manufacturing
economies. It is envisaged that the working speed range of
the motor and compressor may extend to the region of 30,000
rpm. Because the unit operates at such high speed lt is pos-
sible to achieve a high horse power output in a small size and
also to achieve a high compression ratio from a lightweight
and compact unit. Even in the least efficient example of the
preferred form of the invention, i.e. with a single stage
compressor operating at 8,000 rpm, it has been shown that an
output pressure of 140 psi may be achieved from an input pres-
sure of 40 psi. This is better than a 3:1 compression ratio
and may be quickly e~tended as the speed of the motor is
increased.
- The polyphase induction motor is also suitable to run
at ideal turbine compressor operating speed and for some
applications it may be desirable to substitute a turbine
compressor for the positive displacement comp~essor described
above. The turbiné compressor is likely to be particularly
suitable for larger stationary applications.
Although the invention has been described in a pre-
ferred form for application to a hea-t pump which may be used
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for the ~ir condi.tioning or heatiny of vehi.cles or any other
air conditioning and he.at pump applications, it will be
appreciated that the invention may also be applied to situations
requiring an efficient and compact refrigeration system. The
invention may be adapted to any refri~eration situation but is
particularly suitable where portable refri~eration is required,
for example fox use with refrigerated shipping or transportation
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Turning now to Figs. ~ tol~, the preferred embodi-
ment of a control system 112 for the heat pump motor 110 will
now be described. A block diagram of the control system of the
preferred embodiment is illustrated in Fig. 1 and, in addition,
the interconnection of the detailed circuit diagrams illustrated
to Figs. 6 to 9 is also illustrated in Fig. 5.
- ~n oscillator 1 provides a pulse train to a logic
supply ~ and also to a phase controller 6. The logic supply 2
converts the 12 volt DC voltage available at the vehicle batt-
10 ery B14 to a 5 volt DC supply re~uired for some of the various
integrated circuits forming the control system 112. A master
clock 3 supplies a pulse train of variable pulse repetition
rate to a phase sequencer 5, both the master clock 3 and phase
sequencer 5 being controlled by switch controls 4. ~ terminal
; TS of the master clock 3 permits a feedback signal derived in
any kno~n fashion to control the pulse xepetition rate of the
master cloc~ 3. The output of the phase sequencer 5 is passed
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to a phase controller 6 which provides correctly timed switch-
ing signals to a main switch 7 which connects each phase of the
20 nine phase delta, or preferably mesh, connected induction motor
110 to the correct terminals of the vehicle battery B14 in the
correct sequence as will be explained here1nafter in detail.
In Fig. 6 the circuit details of the oscillator 1
and logic power supply 2 are shown. The oscillator 1 comprises
IC13 (National 555) and resistors R114 and R115 together with
capacitor C119. IC13 oscilates with a pulse repetition rate
in the range of 60K Hz to 160K Hz, this rate being governed
by the resistance value of resistors R114 and R115 in series
which charge ca~acitor C119 until a threshold voltage is
reached on the capacitor Cll9 which then discharges through
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resistor R11~, this cycle being repeated.
The remainder of the circuit illustrated in Fig. 6
comprises the logic supply 2 and it will be seen that the out-
put from IC13 is passed to a divide-by-2 flip flop IC14A which
divides the oscillator pulse repetition rate by 2 and, in
addition, has complementary outputs with a precise 50% duty
cycle.
The output of IC14A is passed to a DC to DC converter
which comprises a push-pull arrangement operating through a
transformer Tlll in which both the primary and secondary wind-
ings are centre tapped. The outputs of IC14A are each passed
through a series connected resistor and capacitor (R116 and
CllO together with R117 and Clll) to respective buffer tran-
sistor switches ~111 and Q112. The series connected resistor
and capacitor prevent overload o.f the buffer transistors Qlll
and Q112 in the event of failure of either IC13 or IC14A and
also in the event of low input voltage to IC14A. Resistors
R118 and Rll9 in the collector circuits of transistors Qlll
and Q112 respectively reduce the load on the outputs of IC14A
and also limit the current through transistors Qlll and Q112.
It will be seén that transistors Qlll and Q112
toge~her with their respectively connected switching transist-
ors Q113 and Q114 permit current to flow through their res-~
pective halves of the primary winding of transformer Tlll in
alternate directions at a rate yoverned by the output of IC13
via IC14A~ Inductors Llll and L112 in.the collector circuits
of transistors Q113 and Q114 respectivel~ present a high
impedance to any parasitic oscillations whilst capacitors C112
and C113 introduce positive feedback to the bases of transist-
ors Q113 and Q114 so as to reduce their switching times by
removal of charge from their base-emitter junctions. Resistors
R112 and R113 dampen this positive feedback to prevent self-
oscillation. ~iodes Dll9 and D110 protect transistors Q113 and
Q114 from any induced voltages of high magnitude and reverse
polarity, and also permit current to decay after the transist-
ors Q113 and Q114 have been switched off.
Transformer Tlll has a ferrite core and is a step-
down transformer having only half the number of secondary wind-
ings relative to the number of primary windings. Accordingly,
a time varying vol-tage of approximately 6 volts a~pears across
the secondary winding and this voltage is rectified by diodes
Dlll and D112 and smoothed by capacitor C114 to provide a 5V
supply for some of the integrated circuits used throughout the
control system. The lnterconnection of the logic power supply
2 to the re~aining integrated circuits is not illustrated in
detail and will be clear to those s~illed in the art. -~
As seen in Fig. 7, the switch control~ 4 include a
manually operated 3 position switch having ganged contacts Sl
and S2, the centre position represents an OFF position whilst
the two operative positions represent COLD (forward) and HOT
(reverse).
It will be seen that operation of the s~itch controls
4 causes one of capacitors C121 or C122 to be charged via
resistors R121 or R122 respectively to the 12V supply from the
vehicle hattery B14 whilst simultaneously the other one of
capacitors C121 and C122 is discharged via diode D121 or D122
respectively to ground. In conse~uence, the in-put of only one
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of two Schmitt trigyers IC9A and IC9B goes positive thereb~
causing the output of AND ya-te IC8 B,C to go negative. This
change of logic state is passed via inverter ICllD to divide-
by 2 flip flop IC14B of Fig. 8 to enable same. In addition,
the change of logic s-tate is passed via resistor R123 and diode
D123 to the positive input of integrator IClA.
The integrator IClA is connected to provide a voltage
ramp to series connected resistors R126 and R127 which is
initially positive and reduces in magnitude within increasing
time. The change of logic state produced by ~ND gate IC8B,C
ensures that a maximum positive voltage is initially present
at the output of integrator IClA thereby ensuring that the
master clock IC2 is slowed to a low starting speed in the
vicinity of 200Hz. As the voltage on the positve input of
the integrator IClA decays, due to the charging of capacitor
C123, simultaneously the voltage at the negative input of
integrator IClA rises due to current through resistor R125 and
diode D125 discharging the capacitor C124. In consequence, th~
voltage at the output o integrator IClA falls, thereby causing
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the voltage at the ~unction o~ resistors R126 and R127 to fall
and producing an increase in the pulse repetition rate of the
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master cloc~ IC2 to a preset maximum. This preset maximum will
be be determined by the preset value of resistor R120 and also
by a voltage applied to the terminal TS by a conventional temp-
erature sensor (not illustrated).
The master cloc~ IC2 is an LM322 timer operating in
an astable mode by feeding a fraction of its output bac~ to
its trigger input via capacitor C126. The operating frequency
of the master clock IC2 is 1/(R120+R129).(C125) Hz whilst the
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output is a narrow negative pulse o width approximately
2(R128).(C126) seconds.
The output of the master clock IC2 is passed directly
to line l~ of Fig. 8' and also to two cascaded counters IC3 and
IC4 via a potential divider formed by resistors R1212 and R1213.
The outputs of counters IC3 and IC4 are connected to the address
'inputs of three memories IC6, IC7 and IC12. The counters IC3
and IC4 always count in the same direction and are reset by
NAND gate IC8A~
10It will be seen that the output of Schmitt trigger
- IC9B is connected to flip flop IC5 which determines whether
. forward or reverse operation is to ta]~e place. This is achiev-
ed by the output of fli flop IC5 comprising the most signifi-
cant bit of the address input to memories IC6, IC7 and IC12,
as illustrated in Table I~ The reseting of the counters IC3
and IC4 via NAND gate IC8A is the same for both forward and
reverse functions, however, the output of flip flop IC5
switches the memories IC6, IC7 and IC12 to two distinct and
dlfferent fields of addresses where the forward.and reverse
programmes respectively are stored.
It will be seen from Table I that the outputs of the
memories IC6, IC7 and IC12 comprise 9 bits and the complement
of each of these bits is provided by nine inverters IClOA to
IClOF and ICllA to ICllC respectively. The output,bits of-
the memories IC6, IC7 and IC12, and their complements, are
passed directly to the phase controller 6 illustrated in Fig.
8 .
In addition, the output of integrator IClA of Fig.
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-7 is passed via resistor R1~14 to Schmi-tt triyger IC9C, the
output of which is connected to the base of transistor Q125.
The collector of transistor Q125 is connected to the 12V supply
whilst the emitter transistor Q125 is connected to line Z of
Fig. 8 . The volta~e ramp appearing at the output of integrat-
or IClA initially enables Schmitt trigger IC9C thus turning
transistor Q125 ON. Therefore initially line Z of Fig. 8 is
effectively connected to the 12V supply, however after a pre-
determined delay, transistor Q125 is turned OFF, thereby
effectively disconnecting line Z of Fig.-8- from the 12V
su~ply.
In Fig. 8 , the circuit details of the phase con-
- troller 6 are illustrated, however, only the details of a
single phase of the 9 phases of the preferred embodiment are
illustrated in order to avoid repetition.-
Some aspec-ts of the circuit of Fig. 8 are similar
to the circuit of Fig. 6 . ~ divide-by-2 flip flop IC14B is
provided and, like the divide-by-2 flip flop IC14~ of Fig. 6~,
IC14B is also connected to the output of IC13 of Fig. 6 which
comprises the output of the oscillator 1 of Fig. 5 . In
- addition, the output of invert0r ICllD of Fig. 7 is also
connected to IC14B in order to provide an on/off control for
the operation of the divide-by-2 -flip flop IC14B.
In a manner similar to that of Fig. 6~, the outputs
of flip flop IC14B of Fig. 8 are passed via series connected
capacitors and resistors C131 and R135, R136 respectively,
to transistor switches Q135, Q136 and Q137, Q138 respectively.
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These transistor switches switch the lines X and Y of Fig. 8
to ground alternately at half the rate determined by the pulse
repetition rate of the oscillator 1.
Each phase of the phase controller 6 comprises two
identical circuits which'are required to produce complementary
outputs for the two switches per phase terminal of the main
switch 7 illustrated in detail in Fig. 9 . Each of the
identical circuits of the phase controller 6 comprises one of
bistables IC15 to IC32 respectively and one of transformers
T131 to T149 respectively togetner with associated circuitry.
Each of the bistables IC15 to IC32 comprises a National 555
- which is switchable between a monostable state and a set-reset
flip flop state.
The trigger input of each bistable IC15 to IC32 is
connected to line W and therefore receives the output of
master cloc~ IC2. In addition, the output and input of the
inverter for eacn phase of the phase sequencer 5 are connected
to the inhibit/enable input of the corresyonding bistable for
~that phase. Thus the outpu-t (IClOA) of inverter IClOA is
connected to the inhibit/enable input of bistable IC15 and
~ ~ the input (IClOA) of inverter IClOA is connected to ~he inhibit/
;~ enable input of bistable IC16.
.
Each of the bistables IC15 to IC32 is respectively
connected to the line Z by means of a respective resistor.
For example bistables IC15 and ICl~ are connected to the line
Z by means of resistors R1324 and R1235 respectively. ~he out-
put of each bistable IC15 to IC32 is connected to the centre
tap of the primary w-ndlng of the corresponding transformer and
., -, . '
- 20 -
-, .. :
,
-.
3~
therefore the output of bistable IC15 is connected to the
centre tap of the primary winding of transformer T131.
In order to avoid the voltage drop of the diodes D111
; and D112 of Fig. 6, transistors Q131 and Q132 are connected
to the secondary winding of transformer 131 with resistors
R131 and R132 respectively providing base current in order to
saturate the transistors Q131 and Q132 when they are required
to conduct. In this way the low collector-emitter saturation
voltage of the transistors replaces the relatively larye
forward voltage drop of the diodes, thereby avoiding a sub-
stantial power loss.
After operation of the switch controls 4 as described
in detail with reference to Fig. 7, line Z is initially conn-
ected to the 12V supply and therefore each of bistables IC15
to IC32 operates as a monostable producing a pulse of predeterm-
ined duration for each pulse applied to the trigger input via
line W.
Thus when bistable IC15 is enabled by the output
IC101~, for each pulse produced by master clock IC2 a corres-
ponding pulse of predetermined length appears at the output of
bistable IC15 and is applied to the centre tap of the primary
wlnding of transformer T131. However, wnen bistable IC15 is
inhibited by the output IClOP. no pulses are applied to the
transformer T131. ~ecause of the complementary relatlonship
be-tween outputs IClOA and IClOA, either bistable IC15 is enabl-
ed and bistable IC16 is inhibited or visa versa.
During the initial starting time the pulses produced
by master clock IC2- increase in repetitio~ rate and thus tne
output of
21
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33~ii
,, .
each of the bistables IC15 to IC32 comprises a pulse train in
which there are a plurality of pulses for half the period and
no pulses for the remainder of the period, the mark space ratio
of the plurality of pulses increasing as the frequency of the
master clock IC2 increases.
In this way the pulse w~ eform illustrated in Fig.-10
(to be described hereinafter) is altered so that the effective
voltage of each half period pulse is reduced by modulation.
The modulation is such that the effective applied voltage is
reduced from its maximum possible value by the provision of an
adjustable number of short pulses each of the same duration
during the time allocated for the half period pulse present
during normal operation.
The abovedescribed modulation permits the motor 110
to be s-tarted smoothly and run up to maximum speed. Thus
initially an effective phase voltage of only 0.3V is applied
compared with an effective full speed phase voltage of 12V.
Furthermore, the initial start up period is able to
be adjusted, as is the maximum speed, so that the control system
is able to drive a wide range of loads under different condit-
ions. The use of feedbac~ terminals TS permits this adjustment
to be automatically achieved by means of conventional feedback
techniques.
This initial method of operation continues until the
line Z is disconnected from the 12V supply after a predeter-
mined time thereby causing each of bistables IC15 to IC32 to
operate in a set-reset flip flop mode. In this mode, the first
pulse received by bistable IC15, for example, causes a single
pulse to be applied to the centre tap of the primary winding
of the transformer T131, the duration of this pulse being
, . .
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3~
determined when output IC10~ resets bistable IC15. Thus the
output of each bistable IC15 to IC32 comprises a square wave o~
50~ mark space ratio.
This timing sequence is used to permit the motor 110
to be started at a low speed and then, after the abovementioned
predetermined period, be operated at a faster speed.
It will be apparent to those skilled in the art that
the circuitry associated with each of the transformers T131 to
Tl~9 is very similar to that described in Fig. 6 save that there
10 is not filtering of the output of the secondary winding. Thus
for transformer T131, the output voltage a~appearing between
the centre tap of the secondary winding of transformer T131
and the emitters of transistors Q131 and Q132 is an amplified
or attenuated reproduction of the output voltage of the bi-
stable IC15. The degree of such amplification or attenuation
is dependent upon the turns ratio of each of transformers T131
t~ Tl~9. In additi~n, the
.
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- 10~1836
outpu-t voltage a of transformer T132 is the complement G~ vol-
tage a.
The main switch 7, to which the phase controller 6 of
Fig. 8 is connected, is illustrated in detail in Fig. 9
The main switch ~or 9 phases A, B, C, D, E, F, G, H and I" each
spaced 40 apart in time, comprises two transistor switches
for each phase. ~or phase A one transistor switch comprises
transistor Q141 together with resistor R141 and diode D141
whilst the other switch comprises transistor Q142, resistor
R142 and diode D142. The phase terminal A of Fig. ~ is
connected to the winding of phase A of the 9 phase delta, or
preferably mesh, connected induction motor 110, however, if
desired another type of polyphase motor such as a synchronous-
motor could be used instead. -~
The voltage a is applied to resistor R141 of Fig.-9 ,
that is the emitter of transistor Q141 iS connected to the
centre tapping of the secondary winding of transformer T13I
whilst the base of transistor Q141 is connected to the emitters ~-
~ of transistors Q131 and 132 of Fig. 8. Similarly voltage a
(the complement of voltage a) is connected across resistor
1~142.
When voltage a is positive transistor Q141 is turned
ON thereby connecting phase terminal A to -the positive terminal
o~ the vehicle battery ~14. At the same time as voltage a
ceases to be positive, voltage a becomes positive and therefore
transistor Q141 turns OFF whilst transistor Q142 turns ON there-
by connecting phase terminal A to the negative terminal of
battery B14. In this way a pulsed voltage waveform as illus-
,, .
, '' .
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trated in Fig. 10 is generated for each phase. ~ecause of the
inductance of each winding to which the pulsed waveform is
applied and the interphase coupling, the current for each phase
is substantially sinusoidal. The diodes D141 and D142 are
provided to ~ermi-t currel1t to flow when transistors Q141 and
Q142 have been turned OFF respectively.
It will be apparent tha-t the rate at which transistors
Q141 and Q142 are switched is the rate determined by the master
clock IC2 of Fig. 7 and therefore this rate determines the
speed at which the induction motor 110 operates.
Furthermore, the pair of switches for each phase are
operated so that each switch of a pair is turned on and off
alternately, however, corresponding switches of each pair are
operated ln sequence so that there is identical time displace-
ment between each phase resulting in the voltage waveform for
each phase as illustrated in Fig. 10, except durin~ the initial
start up.
The preferred make and type for each of the integrat-
ed circuits referred to above is as follows:-
ICl(A)National 3900
IC2 " LM322
IC3 " 74LS163
. .
IC4 " 74LS163
; IC5 " 4027
IC6 Harris HM7611
- IC7 Harris HM7611
IC8(A-C) National 7400
IC9(A-C) National 74C14
IC10(A-F) National 7404
.- '
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.' - : ~ ' '
8~i
ICll~A-D) National 7404
IC12 Harris HM7611
IC13 National 555
IC14(A-B) National 4027
IC15-IC32 National 555
It wlll also be apparent to those s]cilled in the art
that the two cascaded counters IC3 and IC4 and the memories
IC6, IC7 and IC12 can be replaced by a shift register in which
a word, comprising twice the number of bits as the memory out-
put, is initially stored in the shift register when power is -
applied to the circult and this word is shifted cyclically at
a rate determined by the master cloc~. In this way an output
: identical to that o~ memories IC6, IC7 and IC12 can be
obtained. In this arrangement reversal of the motor 110 is
achieved by reversing the shift direction of the shift register.
~he same res~lt _s lso able to be achieved with data selectors.
;, .
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