CA1037557A - Control of rotary-field electric machines - Google Patents
Control of rotary-field electric machinesInfo
- Publication number
- CA1037557A CA1037557A CA237,496A CA237496A CA1037557A CA 1037557 A CA1037557 A CA 1037557A CA 237496 A CA237496 A CA 237496A CA 1037557 A CA1037557 A CA 1037557A
- Authority
- CA
- Canada
- Prior art keywords
- control
- arrangement according
- inputs
- stator current
- vector
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/06—Rotor flux based control involving the use of rotor position or rotor speed sensors
- H02P21/10—Direct field-oriented control; Rotor flux feed-back control
Abstract
ABSTRACT
Disclosed is an arrangement for producing, in a rotary-field elect-rical machine, a stator current vector having an effective position between actual positions. The arrangement produces a stator current vector which can occupy alternately two adjacent actual positions at respective opposite sides of an effective position, and controls the durations for which the vector occupies the two adjacent actual positions thereby to control its effective position. A first signal generator generates a first periodic signal synchronised with the frequency of the electrical machine stator current, a second signal generator generates a second periodic signal hav-ing a higher frequency than the first periodic signal and a comparator coupled to the first and second signal generators compares the values of the first and second periodic signals. A change-over switch is arranged to be controlled in dependence upon the comparator for switching the stator current vector between the two adjacent actual positions in dependence upon the relationship between the values of the first and second signals.
Disclosed is an arrangement for producing, in a rotary-field elect-rical machine, a stator current vector having an effective position between actual positions. The arrangement produces a stator current vector which can occupy alternately two adjacent actual positions at respective opposite sides of an effective position, and controls the durations for which the vector occupies the two adjacent actual positions thereby to control its effective position. A first signal generator generates a first periodic signal synchronised with the frequency of the electrical machine stator current, a second signal generator generates a second periodic signal hav-ing a higher frequency than the first periodic signal and a comparator coupled to the first and second signal generators compares the values of the first and second periodic signals. A change-over switch is arranged to be controlled in dependence upon the comparator for switching the stator current vector between the two adjacent actual positions in dependence upon the relationship between the values of the first and second signals.
Description
S5~7 The present invention relates to ~he control of rotary-field ;
machines.
~ur Canadian patent Application Serial No. 177,060 filed July 23, 1973 concerns an arrangement for producing, in a rotary-field electrical ;~
machine, a stator current vector having an effective position between actual -~
positions, the arrangement comprising means for producing a stator current ~ ^
vector which can occupy alternately two adjacent actual positions at respect-ive opposite sides of an effective position, and control means for control-ling the durations for which the vector occupies said two adjacent actual `
positions, thereby to control its effective position. -~ ~
1~ According to the present invention, in an arrangement as defined ~- ;
in the preceding paragraph the control means comprises a first signal genera- ;
tor for generating a first periodic signal synchronised with the frequency ~ ;
of the electrical machine stator current, a second signal generator for generating a second periodic signal having a higher frequency than the first periodic signal, a comparator coupled to the first and second signal genera- ;
tor for comparing the values of the first and second periodic signals, and a changeover switch arranged to be controlled in dependence upon the com~
parator for switching the stator current vector between said two adjacent ;~i-actual positions in dep~ndence upon the relationship between the values of ~ -the first and second signals.
Since the stator current vector can be shifted pulsewise backwards and forwards between two adjacent actual positions~ the stator current vector -~
producing means may include an inverter which can be commutated in two modes which correspond to the two possible directions of current vector rotation.
According to a preferred embodiment, an arrangsment according to the present invention may be provided in conjunction with a control arrange~
ment as illustrated and described with reference to Figures 4 and 5 of the Pa~ent, or a control arrangement which is the operational equivalent thereof.
The latter arrangement may control the stator current vector po~ition at high stator current frequencies, while the arrangement according to the present . , , ~ ~
- . : . . . .
16~3~557 invention may control its position at lower stator current frequencies. As stator current frequency increases the harmonics of the torque lose signifi-cance and it is possible to change-over control from one to the other of the two arrangements. I~ order to avoid a sudden phase change in the stator current in this change-over it is possible to provide, where an inverter comprising n controllable inverter rectifier elements is employed in the vector producing means, a first group of control voltages and a second group ;`
of control voltages for the individual rectifier elements, the control voltages of the first group being electrically in advance of the corresponding control voltages of the second group by 180/n. The two groups of control voltages are for the low-speed and high-speed control of the stator current vector and the two groups can be changed-over, to determine which group is to be effective, by means of a further threshold value~signalling device ~`
which is acted on by a speed-proportional input signal and which is arranged ;;
to actuate a change-over switch. -It has been found particularly advantageous to employ in the vector producing means of an arrangement according to the present invention a novel type of inverter in the form o~ a three-phase current bridge comprising six -~
thyristors, wherein six diodes are connected in series with respective ones of the six thyristors and the thyristor anodes of one bridge half are ~
interconnected, and the thyristor cathodes of the other bridge half are ~ ;
interconnected~ by respective capacitors. Such an inverter is also suitable for other applications in which it becomes necessary during operation to change the phase sequence of the three-phase load supplied by the inverter.
.',"~
For a better understanding of the invention and to show how the ~ `
same may be carried into effect reference will now be made,by wa~ of example, , .~
to the accompan~ing drawings in which~
Figure 1 shows in simplified form an arrang~ment according to the ~ . .
present invention in operable combination with an electrical machine;
Figure 2 is a vector diagram associated with the electrical machine .,.
~ , . ,.: .. . .. , . ... : , , ;
~ 7S57 ~ : ~
of Figure l;
Figure 3 shows thyristor control signals produced in the arrange- ;
ment of Figure l; -Figure 4 shows a first circuit for producing the thyristor control ~ --signals of Figure l, and also a sawtooth vol~age;
Figure 5 shows a circuit for producing a relatively high-frequency sawtooth voltage;
Figure 6 shows signals produced in the circuits of Figures 4 and 5;
Figure 7 shows a comparison between the two sawtooth voltages; ~ -Figure 8 shows a second, alternative, circuit for producing the ~ `
thyristor control signals of Figure l;
Figure 9 shows signals produced in the circuit of Figure 8;
Figure lO shows a second alternative circuit for producing the sawtooth voltage as produced in the circuit of Figure 4;
Figure ll shows the sawtooth voltage as produced in the circuit of Figure 10; and Figure 12 shows a third alternative circuit for producing the saw-tooth voltage as produced in the circuit of Figure 4.
Figure 1 shows an as~nchronous machine l with stator windings R,S
and T supplied by an intermediate d.c.-circuit frequency changer as in the embodiment described in the aforementioned Canadian application Serial No.
17?,060. The frequency changer consists of a rectifier GR and a six-pulse inverter WR in the form of a three-phase bridge. There is produced in the direct-current intermediate circuit of the frequency changer, by means of a current controller 2, an impressed direct current I 1 which is then fed through controllable rectifier elements in the form of thyristors Sl to S6 ; of the inverter WR to the stator windings R,S and T of the asynchronous machine 1. Diodes Dl to D6 are connected in series with respective ones of the thyristors Sl to S6 of the inverter WR. The thyristors $~ to S3 provided ` 30 in the positive half of the three-phase bridge arrangement are connected on ~;
: ;
~3~
, ` ' `~:
1~37~5~
the cathode side to respective ones of commutating capacitors ~1 to C3, while in the other, negative, half of the three-phase bridge arrangement ~he anodes of the thyristors S4 to S6 are connected together by means of respective commutating capacitors C4 to C6. This arrangement has the property that any two thyristors, of which one is situated in one bridge half and the other in the other bridge half, can be fired at any time. The commutating capacitors Cl to C6 are then always charged with the oorrect polarity in such manner that, on firing of another thyristor, the thyristor which was previously ~`~
conducting in the same bridge half is extinguished. -The gate terminals gl to g6 of the thyristors Sl to S6 can be sub-jected either to a first group of control voltages Al to A6 or to a second group of control voltages Bl to ~6, depending upon the position of a change-over switch 4. The change-over switch 4 is actuated by a threshold value ;~
signalling device 5, to the input side o~ wh:lch there is applied a voltage ~ , .
Un proportional to the stator current frequency of the asynchronous machine 1. When the stator current frequency has a value corresponding to a value higher than the response threshold nl of the threshold-value signalling ~
device 5, the change-over switch 4 is actuated thereby and the gate terminals ~-gl to g6 of the thyristors Sl to S6 are acted on by the control voltages Bl to B6. On th~ other hand, the change-over switch 4 is brought into the `
:~ :
position illustrated in Figure 1, in which the control voltages Al to A6 ;
act on the gate terminals gl to g6, ~henever the value of the voltage U
~ ~
is below the response threshold nl, which is the case when the stator current ;~
frequency is at a correspondingly low value.
For periodic change-over between two adjacent discrete ac~ual , positions of the stator current vector there is provided a fur$her change~
over switch 6 which is arranged to be actuated by a threshold-value signalling device ?. There is applied to the input of the threshold-value signalling device 7, in a manner which will hereinafter be described in detail, the ~ ;
difference formed in a mixing element 8 (which is for example an operational -4- - ~
:. ' ' ~Le)37557 ~
amplifier) between an output signal SZf of a sawtooth gener~tor synchronised with the stator current frequency, and an output signal SZ of a further sawtooth generator which operates at a higher frequency.
The firing sequence of the thyristors Sl to S6, and hence the effect and therefore general form of their control voltages Al to A6 and Bl to B6, `~ -may be seen from Figure 2 and wqll be described, by way of example, with ~ "
reference to one revolution of the stator current vector: There is used ~ :
as a reference axis the winding axis of the phase R, and the respective angle of the stator current vector in relation to this axis is denoted by ~ t = 2 t, wherelU is the angular frequency and T is the period of revolution of .'`'`" ', .' the stator current vector. The six possible discrete actual positions of the resultant stator current vector are denoted by vector arrows Ll to L6 and are produced at each firing of the pair of thyris~ors indicated in Figure 2 at these vector arrows. In order that the stator current vector may move in the anticlockwise direction, starting f`rom ~ t_= 0, in jumps of 60 , it would thus first of all be necessary to put the thyristors Sl and S6 in the con-ducting condition, then the thyristors S2 and S6, thereafter the thyristors ;
S2 and S4, and so on. In the angular ranges denoted by I to VI the thyristors ~ -must be fired in the indicated manner and, with the use of a continuously rotating preset control vector for the stator current vector, the latter is brought into its next possible actual position, as seen in the anticlockwise direction, as soon as the control vector exceeds the limit of one of these ranges. This takes place in the state of operation in which the threshold~
value signalling device ~bnQte~ by 5 in Figure 1 has responded, i.e. at higher stator current frequencies. To this extent, this manner of operation corresponds to that embodiment illustrated and described in the aforemention~
; ed Canadian application 177,060, to which reference should be made if more information is desired.
~ However, when the frequency of the stator current falls below the ; 30 response value nl of the threshold-value signalling device 5, a quasi-contin~
~, ..
:
~)31755'7 uous con~rol of the stator current vector takes place in pulsed mode, in such manner that the vector is periodically charlged over between two adjacent `~
discrete actual positions with continuously varying pulse duty ratio, the two adjacent positions being at the extremeties of one of the ranges denoted by I to VI . These ranges have a phase difference of ~/6, i.e. a time dif-P P
ference of T/12, in relation to the ranges I to VI in order to avoid a sudden phase change in the stator current. Thus, when the previously mentioned preset control vector enters for example the range denoted by Ip, the thyristor S6 is rendered continuously conducting and the thyristors Sl and S2 are fired alternately in rapid sequence. Whenever the preset control `
vector is situated in that half of the range Ip between 7~/6 and 7f/3, the ~` ~
stator current vector occupies the position Ll for a longer time than the ~ `
position L2. Whenever the angular position of the preset control vector is 7~/3, the times for which the stator current vector remains in the positions ;~
L1 and L2 are exactly equal, and for the second half of the range Ip the control current vector occupies the position L2 for a longer time than the position Ll. Since the ratio of the times of stay of the stator current vector in the discrete actual positions Ll and L2 determines its effective '~
position intermediate Ll and L2, the latter can be quasi-continuously varied -`
between these two positions Ll and L2, if the ratio of the times of stay of -~
the vector in these two positions is correspondingly changed. Similar considerations apply to the remaining ranges ~f pulsed operation which are denoted by II to VI , that is to say, in which ranges the change-over switch 6 in Figure 1 is continually periodically actuated by the threshold-value signalling device 7 in dependence upon the difference between its input signals SZf and SZp.
Figure 3 is a pulse diagram for the control voltages Al to A6 and and Bl to B6 which are necessary in the previously described modes of operation and which are applied through the change-over switches 6 and 4 illustrated in Figure 1 to the gate terminals gl to g6 of the thyristors ', ~'.:
~3~S57 ;~
Sl to S6. The control voltage group Al to A6 is utilised for pulsed operat-ion at low frequencies and consists of six square-wave pulse voltages of the duration 2 ~f which are offset from one another by ~ as shown in Figure 3. The same applies to the second control voltage group Bl to B6, each of the control voltages o~ this group being offset from a corresponding control voltage of the first group by ~. In addition, there are plotted in Figure 3 the angular ranges I to VI (unpulsed operation) and I to VI
(pulsed operation), which represent the correspondingly designated angular ranges of Figure 2.
The mode of energisation of the individual gate terminals of the ~ -thyrsitors of the inverter WR will now be described in detail by way of example with reference to the angular range Ip. Of the control voltage group Al to A6, only the control voltages A2 and A3 carry a firing signal in this ~^ anngular range I , so that the thyristors S6 and S2 are fired when the change-over switch 6 is in the position illustrated in Figure 1, while the thyristors Sl and S6 are fired when the change-over switch 6 is in its other position.
Since the position of the change-over switch 6 is continually periodically changed, the thyristors Sl and S2 are therefore alternately fired in the annular range I , while the thyristor S6 is continuously conducting.
1 If the stator current frequency is so high that the response thres-~ 20 hold nl of the threshold-value signalling device 5 is exceeded, the change-over switch 4 is brought into its other position and the gate terminals of the thyristors Sl to S6 are then energised in unpulsed mode by the second ~; control voltage group Bl to B6, of which only the control voltages Bl and ;-B2 are operative in the angular range I, so that the thyristors Sl and S6 are ,~
'~ fired, as will be seen by a comparison with Figure 1. Thus, in this angular range3 the stator current vector occupîes the position denoted by Ll. ;~
Figure 4 illustrates a simple embodiment of a control set by which the two voltage control groups ~1 to ~6 and Bl to B6 and the frequency-synchronised sawtooth generator signal SZf can be produced. This control set consists substantially of a voltage-frequency convertor 9, the output signal ' :
-7_ '!. : ,, ~3~5~
of which acts on the inputs of two six-stage ring counter~10 and 11. The stator current frequency of the rotating-field machine ' i9 indicated by the unidirectional voltage U applied to the input of the voltage-frequency converter 9. This voltage U is applied, both directly and through an amplif- -ier 12 which changes the voltage polarity, to a change-over switch 13 which ; is actuated by the output signal of a bistable trigger stage 14. The bistable trigger stage 14 is activated by the output signals of two limit- `
value signalling devices 15 and 16, one of which has a response threshold h and the other a response threshold 0. The input signals of the limit-value signalling devices 15 and 16 consist of the output signal of an ~.
integrator 17, which depending upon the position of the change-over switch - -13, varies periodically and linearly with respect to time from the value 0 `~ :
. to the constant value h determined by the response threshold of the limit- ;
~ value signalling device 15, and from this value h back to the value 0.
`t Whenever the output signal UI of the integrator 17 reaches one of these values ,';
the change-over switch 13 is actuated by the output signal UB of the bistable : tri.gger stage 14, UB being a square-wave pulse voltage having a pulse duty factor of 1, If the ring counter 10 is stepped forwards by each rising edge of the square-wave pulse voltage UB, and the ring counter 11 is stepped for-20~ards by each of the falling pulse edges of this voltage U , the control :
~' B
voltages Al to A6 as shown in Figure 3 can be derived in known manner from . the output of the ring counter 10, and the control voltage Bl to B6 as shown : in Figure 3 can be derived similarly from the output of the ring counter 11.
If the periodicity of the square~wave pulse voltage U is denoted by T/6, : B
then T is the periodicity o~ t~e st2tor c~re~t ~nd the ~ e ~tage ~B ca~
be regarded as a digital representation of the angular position of the preset .~
stator current vector rotating with the period T.
The output signal UI of the integrator 17 is applied~ directly and .
through an amplifier 19 which reverses its polarity~ to two contacts of a change-over swi~ch 18 which is also actuated by the output signal of the ;~ ;
'.''`; `
1{~3 7557 bistable trigger stage 14 for the production of the stator current frequency- ~ -synchronised sawtooth signal SZf. ~ -Figure 5 illustrates a generator f~r the production of the second sawtooth signal SZ . This sawtooth generator consists of a voltage-frequency convertor of the type illustrated in Figure 4, but in which the two limit-`- value signalling devices 20 and 21 have symmetrical response values +h and -h respectively and the polarity of the output~signal of the integrator 22 is ` ;-not changed. The input voltage U is a constant voltage and is so adapted to the integration time of the integrator 22 that the signal SZp has a sub-stantially higher repetition frequency that the frequency-synchronised saw- -~
tooth generator signal SZf. The generator also comprises a change-over switch 23, an amplifier 24, and a bistable trigger stage 25.
Figure 6 illustrates the variation, as a function of time, of the output voltage UI of the integrator 17, of the output voltage UB of the bistable trigger stage 14 and of the sawtooth signals SZf and SZ . It can -be seen how the output voltage UI varies in t:riangular form with the periodicity T/6, between the values 0 and h, which then results in the square-wave pulse output voltage UB of the bistable trigger stage 14, owing to the limit-value signalling devices 15 and 16 and the bistable trigger stage 14. Since the polarity of the integrator output voltage U is reversed at each instant tu by the change-over switch 18 actuated by the bistable trigger stage 14, the signal SZf is given a sawtooth form with a vertical negative-going edge and a positive-going edge extending linearly between the limits -h and +h~ In the case of the signal SZ , a triangular signal is obtained between the limits -h and +h.
The dif~erence, formed in the mfixing stage 8 illustrated in Figure 1, between the frequency-synchronised sawtooth signal SZf and the higher-frequency sawtooth sifgnal SZ is employed for the periodic actuation of the change-over switch 6 in the pulsed mode of operation. Figure 7 helps explain ;~
this. During each of the times in which the signal SZ exceed the signal ,, ~9~ :
.-', : ' ~ . .
~ ~375~i7 SZf there appears at the output of the limit-value signalling device 7 (see Figure 1) a signal which brings the change-over switch 6 from the position illustrated in Figure 1 into its other position. During each of the times when the signal SZ is lower than the signal SZf no signal appears at the output of he limit-value signalling device 7 and therefore the change-over switch 6 occupies the position illustrated in Figure 1. In this position, -~
for example, the rectifier elements S2 and S6 would be in the fired condition -in the angular range Ip, while the rectifier elements Sl and S6 would be in ~-~
the fired condition in the other position of the change-over switch 6. With constant stator current frequency, this would mean that the stator current vector continuously changes over between the actual positions Ll and L2 and the time for which it stays in the position Ll decreases continuously, and with constant stator current frequency it decreases linearly with respect to time, while its period of stay in the position L2 continuously increases.
Thus the effective position of the vector moves continuo~sly from position ~-Ll towards position L2.
For the case where the effective vector position is not to be ` changed, but a constant definite position (for example between Ll and L2) is desired it would be simple at the moment in time, in the travel from Ll to L2 of the effective vector, at which the desired effective vector position is -~ 20 reached to set the condition that the stator current frequency be zero i.e.
Un = The sawtooth SZ then does not rise any more after this moment in time but retains the value it had reached at that moment so that the corres-ponding vector position remains fixed at the desired position.
Instead of the control voltages Al to A6 and Bl to B6 being formed by means of a voltage-frequency converter and two ring counters as shown in Figure 4, they may be formed by means of an angle switch 26, shown in `.... ~- .... .
Figure 8, to the input side of which there are applied component voltages sin ~ and cos ~ of a continuously rotating preset control vector, similar-ly to the manner in which a preset control vector is ulilised in the afore-~' ' ~:' . . .
-10~ , ",, .. .. . .
~ ~375~7 :
mentioned Canadian application 177,060. ~ corresponds to the angular dt frequency ~ Ol the stator current, cos ~ ~' being proportional to that com~
ponent of the preset vector ~lich points in the direction of the winding axis ~ ~ -R of the rotating-field machine 1, while sin ~ is proportional to that component of the preset vector which is perpendicular thereto.
Figure 8 in fact shows the construction of an angle switch which is disclosed in German Patent Specification 1,~41,312, modified for the purposes of the present arrangement. The inputs of four operational amplif-iers 29 to 32 are so connected to input terminals 27 and 28 through corres-pondingly chosed resistances that there is set up at the output of the amplifier 29 a voltage which lags by 30 behind the component voltage sin ~ * -present at the terminal 28, there is set up at the output of the amplifier 30 a voltage which lags by 60 behind the component voltage sin ~, there is set up at the output of the amplifier 31 a voltage which lags by 120 behind the component voltage sin ~, and at the output of the amplifier 32 a voltage which lags by 150 behind the same co'mponent voltage. In addition, ;
there are provided six limit-value signalling devices 33 to 38 of which the `
limit-value signalling devices 35 and 38 are connected to respective ones of the aforementioned component voltages, while the remaining devices 33, 34, 36 and 37 are acted on by the output signals of the amplifiers 29 to 32 respectively. Polarity reversing stages 39 to 44 are connected to the out-puts of the limit-value signalling devices 33 to 38 respectively so that pulse trains WTl to WT12 illustrated in Figure 9 are obtained, these pulse trains being 7t. apart and each pulse corresponding to a half-revolution of the preset vector. In addition, there are provided twelve AN~ gates 45 to 56 each of which is acted on, in the indicated manner, by two of the pulse trains WTl to WT12. Each of the gates 45 to 56 outputs a signal whenever the two pulse trains acting on it have a value different from 0. As can ~ ~
readily be deduced from Figure 9, there are thus set up at nutput terminal ~ ~ ;
57 to 62 of the angle switch 26 the control voltages which are denoted by Al ' , . ~ . , ~1~375S7 to A6 in Figure 3, whilst at the output terminals 63 to 68 the control volt- ~
ages denoted by Bl to B6 in Figure 3 are produced. - `
Figure 10 illustrates an alternative generator 71 for the formation of the frequency-synchronised sawtooth signal SZf. For this purpose the pulse trains WTl, WT3, WT5, WT7, WT9 and WTll and the output signals of the amplifiers 30 and 31 of the angle switch 26 are taken from the output term-inals 69 to 76 of the latter and applied to the correspondingly denoted in-put terminals of the sawtooth generator 77. The component voltage sin ~ ~' of the preset vector is connected to a further terminal. The pulse trains -~
WTl, WT3, WT7, WT9 and WTll are so combined in six AND gates 78 to 83 in the indicat0d manner .that the outputs of these AND gates successively supply, :
each during a period of T/6, actuating signals for six switches 84 to 89 which pass one of six sinusoidal voltages which are 60 apart in phase to ~`
the input of an amplifier 90.
Those portions of the six sinusoidal voltages which are passed by the ` switches 84 to 89 are illustrated in the voltage diagram of Figure 11. Each portion extends from -30 to +30 of the respective sinusoidal voltage. In this range, the sine function has an approximately linear form so that the generator 77 produces approximately the same frequency-synchronised sawtooth voltage form as is shown in Figure 6.
'` A third possible alternative form of a frequency-synchronised saw- ;`~
tooth generator is illustrated in Figure 12. This is based upon the idea of ;~
simulating, from four control voltages of the voltage control group employed ; ~ .
in pulsed operation, two phase currents iR and i9 of a stator current vector which in its rotation occupies six discrete positions which are, however, advanced by an angle of 30 in relation to the positions denoted by Ll to L6 in Figure 2. There are then formed from these phase currents, with due regard to the condition of symmetry iR + iS ~~ iT = ~ two orthogonal components of this simulated stator current vector, and the sine of the difference angle between the position of this vector and the angular position ~f the contin~
uously rotating preset vector is formed therefrom. The sine -12 ~`
... ... .
~ 37~7 ~ :
of this difference angle has a maximum negative value whenever the preset vector reaches any one of the ranges I to VI , always has the value 0 a~ ;
the middle of any of these ranges, and has a m~ximum positive value when the preset vector leaves any of these ranges. There are then obtained, through-out one rotation of the preset vector, voltage forms as illustrated in Figure 11 . -The phase currents iR and i~ are formed by means of two amplifiers 91 and 92, to the inputs of which there are applied the control voltages Al -~:
and A4, and A5 and A2, respectively. By means of a further amplifier 93 there is then formed that component i~ of the simulated stator current vector :
which falls in the direction denoted by L2 in Figure 2, while the other :. component i~ , orthogonal thereto, is assumed to descend in the direction of .~ the winding axis R of the rotating-field machine 1. By means of a vector rotator VD comprising two multipliers 94 and 9S and an amplifier 96, there ! is formed from the two orthogonal components i~ and iB of the simulated stator ~ current vector and the two components, also c\rthogonal, of the control voltage vector sin ~ and cos ~ *, a quantity corresponding to the sine of the angle ~ :
difference between the respective angular positions of these vectors, which quantity appears at the terminal 97 as sawtooth signal SZ~. There again ;~
appear here voltage forms of the kind illustrated in Figure 11. ~`
"' i/ ~,` ' ' -13_ ~ :
:
.
.
machines.
~ur Canadian patent Application Serial No. 177,060 filed July 23, 1973 concerns an arrangement for producing, in a rotary-field electrical ;~
machine, a stator current vector having an effective position between actual -~
positions, the arrangement comprising means for producing a stator current ~ ^
vector which can occupy alternately two adjacent actual positions at respect-ive opposite sides of an effective position, and control means for control-ling the durations for which the vector occupies said two adjacent actual `
positions, thereby to control its effective position. -~ ~
1~ According to the present invention, in an arrangement as defined ~- ;
in the preceding paragraph the control means comprises a first signal genera- ;
tor for generating a first periodic signal synchronised with the frequency ~ ;
of the electrical machine stator current, a second signal generator for generating a second periodic signal having a higher frequency than the first periodic signal, a comparator coupled to the first and second signal genera- ;
tor for comparing the values of the first and second periodic signals, and a changeover switch arranged to be controlled in dependence upon the com~
parator for switching the stator current vector between said two adjacent ;~i-actual positions in dep~ndence upon the relationship between the values of ~ -the first and second signals.
Since the stator current vector can be shifted pulsewise backwards and forwards between two adjacent actual positions~ the stator current vector -~
producing means may include an inverter which can be commutated in two modes which correspond to the two possible directions of current vector rotation.
According to a preferred embodiment, an arrangsment according to the present invention may be provided in conjunction with a control arrange~
ment as illustrated and described with reference to Figures 4 and 5 of the Pa~ent, or a control arrangement which is the operational equivalent thereof.
The latter arrangement may control the stator current vector po~ition at high stator current frequencies, while the arrangement according to the present . , , ~ ~
- . : . . . .
16~3~557 invention may control its position at lower stator current frequencies. As stator current frequency increases the harmonics of the torque lose signifi-cance and it is possible to change-over control from one to the other of the two arrangements. I~ order to avoid a sudden phase change in the stator current in this change-over it is possible to provide, where an inverter comprising n controllable inverter rectifier elements is employed in the vector producing means, a first group of control voltages and a second group ;`
of control voltages for the individual rectifier elements, the control voltages of the first group being electrically in advance of the corresponding control voltages of the second group by 180/n. The two groups of control voltages are for the low-speed and high-speed control of the stator current vector and the two groups can be changed-over, to determine which group is to be effective, by means of a further threshold value~signalling device ~`
which is acted on by a speed-proportional input signal and which is arranged ;;
to actuate a change-over switch. -It has been found particularly advantageous to employ in the vector producing means of an arrangement according to the present invention a novel type of inverter in the form o~ a three-phase current bridge comprising six -~
thyristors, wherein six diodes are connected in series with respective ones of the six thyristors and the thyristor anodes of one bridge half are ~
interconnected, and the thyristor cathodes of the other bridge half are ~ ;
interconnected~ by respective capacitors. Such an inverter is also suitable for other applications in which it becomes necessary during operation to change the phase sequence of the three-phase load supplied by the inverter.
.',"~
For a better understanding of the invention and to show how the ~ `
same may be carried into effect reference will now be made,by wa~ of example, , .~
to the accompan~ing drawings in which~
Figure 1 shows in simplified form an arrang~ment according to the ~ . .
present invention in operable combination with an electrical machine;
Figure 2 is a vector diagram associated with the electrical machine .,.
~ , . ,.: .. . .. , . ... : , , ;
~ 7S57 ~ : ~
of Figure l;
Figure 3 shows thyristor control signals produced in the arrange- ;
ment of Figure l; -Figure 4 shows a first circuit for producing the thyristor control ~ --signals of Figure l, and also a sawtooth vol~age;
Figure 5 shows a circuit for producing a relatively high-frequency sawtooth voltage;
Figure 6 shows signals produced in the circuits of Figures 4 and 5;
Figure 7 shows a comparison between the two sawtooth voltages; ~ -Figure 8 shows a second, alternative, circuit for producing the ~ `
thyristor control signals of Figure l;
Figure 9 shows signals produced in the circuit of Figure 8;
Figure lO shows a second alternative circuit for producing the sawtooth voltage as produced in the circuit of Figure 4;
Figure ll shows the sawtooth voltage as produced in the circuit of Figure 10; and Figure 12 shows a third alternative circuit for producing the saw-tooth voltage as produced in the circuit of Figure 4.
Figure 1 shows an as~nchronous machine l with stator windings R,S
and T supplied by an intermediate d.c.-circuit frequency changer as in the embodiment described in the aforementioned Canadian application Serial No.
17?,060. The frequency changer consists of a rectifier GR and a six-pulse inverter WR in the form of a three-phase bridge. There is produced in the direct-current intermediate circuit of the frequency changer, by means of a current controller 2, an impressed direct current I 1 which is then fed through controllable rectifier elements in the form of thyristors Sl to S6 ; of the inverter WR to the stator windings R,S and T of the asynchronous machine 1. Diodes Dl to D6 are connected in series with respective ones of the thyristors Sl to S6 of the inverter WR. The thyristors $~ to S3 provided ` 30 in the positive half of the three-phase bridge arrangement are connected on ~;
: ;
~3~
, ` ' `~:
1~37~5~
the cathode side to respective ones of commutating capacitors ~1 to C3, while in the other, negative, half of the three-phase bridge arrangement ~he anodes of the thyristors S4 to S6 are connected together by means of respective commutating capacitors C4 to C6. This arrangement has the property that any two thyristors, of which one is situated in one bridge half and the other in the other bridge half, can be fired at any time. The commutating capacitors Cl to C6 are then always charged with the oorrect polarity in such manner that, on firing of another thyristor, the thyristor which was previously ~`~
conducting in the same bridge half is extinguished. -The gate terminals gl to g6 of the thyristors Sl to S6 can be sub-jected either to a first group of control voltages Al to A6 or to a second group of control voltages Bl to ~6, depending upon the position of a change-over switch 4. The change-over switch 4 is actuated by a threshold value ;~
signalling device 5, to the input side o~ wh:lch there is applied a voltage ~ , .
Un proportional to the stator current frequency of the asynchronous machine 1. When the stator current frequency has a value corresponding to a value higher than the response threshold nl of the threshold-value signalling ~
device 5, the change-over switch 4 is actuated thereby and the gate terminals ~-gl to g6 of the thyristors Sl to S6 are acted on by the control voltages Bl to B6. On th~ other hand, the change-over switch 4 is brought into the `
:~ :
position illustrated in Figure 1, in which the control voltages Al to A6 ;
act on the gate terminals gl to g6, ~henever the value of the voltage U
~ ~
is below the response threshold nl, which is the case when the stator current ;~
frequency is at a correspondingly low value.
For periodic change-over between two adjacent discrete ac~ual , positions of the stator current vector there is provided a fur$her change~
over switch 6 which is arranged to be actuated by a threshold-value signalling device ?. There is applied to the input of the threshold-value signalling device 7, in a manner which will hereinafter be described in detail, the ~ ;
difference formed in a mixing element 8 (which is for example an operational -4- - ~
:. ' ' ~Le)37557 ~
amplifier) between an output signal SZf of a sawtooth gener~tor synchronised with the stator current frequency, and an output signal SZ of a further sawtooth generator which operates at a higher frequency.
The firing sequence of the thyristors Sl to S6, and hence the effect and therefore general form of their control voltages Al to A6 and Bl to B6, `~ -may be seen from Figure 2 and wqll be described, by way of example, with ~ "
reference to one revolution of the stator current vector: There is used ~ :
as a reference axis the winding axis of the phase R, and the respective angle of the stator current vector in relation to this axis is denoted by ~ t = 2 t, wherelU is the angular frequency and T is the period of revolution of .'`'`" ', .' the stator current vector. The six possible discrete actual positions of the resultant stator current vector are denoted by vector arrows Ll to L6 and are produced at each firing of the pair of thyris~ors indicated in Figure 2 at these vector arrows. In order that the stator current vector may move in the anticlockwise direction, starting f`rom ~ t_= 0, in jumps of 60 , it would thus first of all be necessary to put the thyristors Sl and S6 in the con-ducting condition, then the thyristors S2 and S6, thereafter the thyristors ;
S2 and S4, and so on. In the angular ranges denoted by I to VI the thyristors ~ -must be fired in the indicated manner and, with the use of a continuously rotating preset control vector for the stator current vector, the latter is brought into its next possible actual position, as seen in the anticlockwise direction, as soon as the control vector exceeds the limit of one of these ranges. This takes place in the state of operation in which the threshold~
value signalling device ~bnQte~ by 5 in Figure 1 has responded, i.e. at higher stator current frequencies. To this extent, this manner of operation corresponds to that embodiment illustrated and described in the aforemention~
; ed Canadian application 177,060, to which reference should be made if more information is desired.
~ However, when the frequency of the stator current falls below the ; 30 response value nl of the threshold-value signalling device 5, a quasi-contin~
~, ..
:
~)31755'7 uous con~rol of the stator current vector takes place in pulsed mode, in such manner that the vector is periodically charlged over between two adjacent `~
discrete actual positions with continuously varying pulse duty ratio, the two adjacent positions being at the extremeties of one of the ranges denoted by I to VI . These ranges have a phase difference of ~/6, i.e. a time dif-P P
ference of T/12, in relation to the ranges I to VI in order to avoid a sudden phase change in the stator current. Thus, when the previously mentioned preset control vector enters for example the range denoted by Ip, the thyristor S6 is rendered continuously conducting and the thyristors Sl and S2 are fired alternately in rapid sequence. Whenever the preset control `
vector is situated in that half of the range Ip between 7~/6 and 7f/3, the ~` ~
stator current vector occupies the position Ll for a longer time than the ~ `
position L2. Whenever the angular position of the preset control vector is 7~/3, the times for which the stator current vector remains in the positions ;~
L1 and L2 are exactly equal, and for the second half of the range Ip the control current vector occupies the position L2 for a longer time than the position Ll. Since the ratio of the times of stay of the stator current vector in the discrete actual positions Ll and L2 determines its effective '~
position intermediate Ll and L2, the latter can be quasi-continuously varied -`
between these two positions Ll and L2, if the ratio of the times of stay of -~
the vector in these two positions is correspondingly changed. Similar considerations apply to the remaining ranges ~f pulsed operation which are denoted by II to VI , that is to say, in which ranges the change-over switch 6 in Figure 1 is continually periodically actuated by the threshold-value signalling device 7 in dependence upon the difference between its input signals SZf and SZp.
Figure 3 is a pulse diagram for the control voltages Al to A6 and and Bl to B6 which are necessary in the previously described modes of operation and which are applied through the change-over switches 6 and 4 illustrated in Figure 1 to the gate terminals gl to g6 of the thyristors ', ~'.:
~3~S57 ;~
Sl to S6. The control voltage group Al to A6 is utilised for pulsed operat-ion at low frequencies and consists of six square-wave pulse voltages of the duration 2 ~f which are offset from one another by ~ as shown in Figure 3. The same applies to the second control voltage group Bl to B6, each of the control voltages o~ this group being offset from a corresponding control voltage of the first group by ~. In addition, there are plotted in Figure 3 the angular ranges I to VI (unpulsed operation) and I to VI
(pulsed operation), which represent the correspondingly designated angular ranges of Figure 2.
The mode of energisation of the individual gate terminals of the ~ -thyrsitors of the inverter WR will now be described in detail by way of example with reference to the angular range Ip. Of the control voltage group Al to A6, only the control voltages A2 and A3 carry a firing signal in this ~^ anngular range I , so that the thyristors S6 and S2 are fired when the change-over switch 6 is in the position illustrated in Figure 1, while the thyristors Sl and S6 are fired when the change-over switch 6 is in its other position.
Since the position of the change-over switch 6 is continually periodically changed, the thyristors Sl and S2 are therefore alternately fired in the annular range I , while the thyristor S6 is continuously conducting.
1 If the stator current frequency is so high that the response thres-~ 20 hold nl of the threshold-value signalling device 5 is exceeded, the change-over switch 4 is brought into its other position and the gate terminals of the thyristors Sl to S6 are then energised in unpulsed mode by the second ~; control voltage group Bl to B6, of which only the control voltages Bl and ;-B2 are operative in the angular range I, so that the thyristors Sl and S6 are ,~
'~ fired, as will be seen by a comparison with Figure 1. Thus, in this angular range3 the stator current vector occupîes the position denoted by Ll. ;~
Figure 4 illustrates a simple embodiment of a control set by which the two voltage control groups ~1 to ~6 and Bl to B6 and the frequency-synchronised sawtooth generator signal SZf can be produced. This control set consists substantially of a voltage-frequency convertor 9, the output signal ' :
-7_ '!. : ,, ~3~5~
of which acts on the inputs of two six-stage ring counter~10 and 11. The stator current frequency of the rotating-field machine ' i9 indicated by the unidirectional voltage U applied to the input of the voltage-frequency converter 9. This voltage U is applied, both directly and through an amplif- -ier 12 which changes the voltage polarity, to a change-over switch 13 which ; is actuated by the output signal of a bistable trigger stage 14. The bistable trigger stage 14 is activated by the output signals of two limit- `
value signalling devices 15 and 16, one of which has a response threshold h and the other a response threshold 0. The input signals of the limit-value signalling devices 15 and 16 consist of the output signal of an ~.
integrator 17, which depending upon the position of the change-over switch - -13, varies periodically and linearly with respect to time from the value 0 `~ :
. to the constant value h determined by the response threshold of the limit- ;
~ value signalling device 15, and from this value h back to the value 0.
`t Whenever the output signal UI of the integrator 17 reaches one of these values ,';
the change-over switch 13 is actuated by the output signal UB of the bistable : tri.gger stage 14, UB being a square-wave pulse voltage having a pulse duty factor of 1, If the ring counter 10 is stepped forwards by each rising edge of the square-wave pulse voltage UB, and the ring counter 11 is stepped for-20~ards by each of the falling pulse edges of this voltage U , the control :
~' B
voltages Al to A6 as shown in Figure 3 can be derived in known manner from . the output of the ring counter 10, and the control voltage Bl to B6 as shown : in Figure 3 can be derived similarly from the output of the ring counter 11.
If the periodicity of the square~wave pulse voltage U is denoted by T/6, : B
then T is the periodicity o~ t~e st2tor c~re~t ~nd the ~ e ~tage ~B ca~
be regarded as a digital representation of the angular position of the preset .~
stator current vector rotating with the period T.
The output signal UI of the integrator 17 is applied~ directly and .
through an amplifier 19 which reverses its polarity~ to two contacts of a change-over swi~ch 18 which is also actuated by the output signal of the ;~ ;
'.''`; `
1{~3 7557 bistable trigger stage 14 for the production of the stator current frequency- ~ -synchronised sawtooth signal SZf. ~ -Figure 5 illustrates a generator f~r the production of the second sawtooth signal SZ . This sawtooth generator consists of a voltage-frequency convertor of the type illustrated in Figure 4, but in which the two limit-`- value signalling devices 20 and 21 have symmetrical response values +h and -h respectively and the polarity of the output~signal of the integrator 22 is ` ;-not changed. The input voltage U is a constant voltage and is so adapted to the integration time of the integrator 22 that the signal SZp has a sub-stantially higher repetition frequency that the frequency-synchronised saw- -~
tooth generator signal SZf. The generator also comprises a change-over switch 23, an amplifier 24, and a bistable trigger stage 25.
Figure 6 illustrates the variation, as a function of time, of the output voltage UI of the integrator 17, of the output voltage UB of the bistable trigger stage 14 and of the sawtooth signals SZf and SZ . It can -be seen how the output voltage UI varies in t:riangular form with the periodicity T/6, between the values 0 and h, which then results in the square-wave pulse output voltage UB of the bistable trigger stage 14, owing to the limit-value signalling devices 15 and 16 and the bistable trigger stage 14. Since the polarity of the integrator output voltage U is reversed at each instant tu by the change-over switch 18 actuated by the bistable trigger stage 14, the signal SZf is given a sawtooth form with a vertical negative-going edge and a positive-going edge extending linearly between the limits -h and +h~ In the case of the signal SZ , a triangular signal is obtained between the limits -h and +h.
The dif~erence, formed in the mfixing stage 8 illustrated in Figure 1, between the frequency-synchronised sawtooth signal SZf and the higher-frequency sawtooth sifgnal SZ is employed for the periodic actuation of the change-over switch 6 in the pulsed mode of operation. Figure 7 helps explain ;~
this. During each of the times in which the signal SZ exceed the signal ,, ~9~ :
.-', : ' ~ . .
~ ~375~i7 SZf there appears at the output of the limit-value signalling device 7 (see Figure 1) a signal which brings the change-over switch 6 from the position illustrated in Figure 1 into its other position. During each of the times when the signal SZ is lower than the signal SZf no signal appears at the output of he limit-value signalling device 7 and therefore the change-over switch 6 occupies the position illustrated in Figure 1. In this position, -~
for example, the rectifier elements S2 and S6 would be in the fired condition -in the angular range Ip, while the rectifier elements Sl and S6 would be in ~-~
the fired condition in the other position of the change-over switch 6. With constant stator current frequency, this would mean that the stator current vector continuously changes over between the actual positions Ll and L2 and the time for which it stays in the position Ll decreases continuously, and with constant stator current frequency it decreases linearly with respect to time, while its period of stay in the position L2 continuously increases.
Thus the effective position of the vector moves continuo~sly from position ~-Ll towards position L2.
For the case where the effective vector position is not to be ` changed, but a constant definite position (for example between Ll and L2) is desired it would be simple at the moment in time, in the travel from Ll to L2 of the effective vector, at which the desired effective vector position is -~ 20 reached to set the condition that the stator current frequency be zero i.e.
Un = The sawtooth SZ then does not rise any more after this moment in time but retains the value it had reached at that moment so that the corres-ponding vector position remains fixed at the desired position.
Instead of the control voltages Al to A6 and Bl to B6 being formed by means of a voltage-frequency converter and two ring counters as shown in Figure 4, they may be formed by means of an angle switch 26, shown in `.... ~- .... .
Figure 8, to the input side of which there are applied component voltages sin ~ and cos ~ of a continuously rotating preset control vector, similar-ly to the manner in which a preset control vector is ulilised in the afore-~' ' ~:' . . .
-10~ , ",, .. .. . .
~ ~375~7 :
mentioned Canadian application 177,060. ~ corresponds to the angular dt frequency ~ Ol the stator current, cos ~ ~' being proportional to that com~
ponent of the preset vector ~lich points in the direction of the winding axis ~ ~ -R of the rotating-field machine 1, while sin ~ is proportional to that component of the preset vector which is perpendicular thereto.
Figure 8 in fact shows the construction of an angle switch which is disclosed in German Patent Specification 1,~41,312, modified for the purposes of the present arrangement. The inputs of four operational amplif-iers 29 to 32 are so connected to input terminals 27 and 28 through corres-pondingly chosed resistances that there is set up at the output of the amplifier 29 a voltage which lags by 30 behind the component voltage sin ~ * -present at the terminal 28, there is set up at the output of the amplifier 30 a voltage which lags by 60 behind the component voltage sin ~, there is set up at the output of the amplifier 31 a voltage which lags by 120 behind the component voltage sin ~, and at the output of the amplifier 32 a voltage which lags by 150 behind the same co'mponent voltage. In addition, ;
there are provided six limit-value signalling devices 33 to 38 of which the `
limit-value signalling devices 35 and 38 are connected to respective ones of the aforementioned component voltages, while the remaining devices 33, 34, 36 and 37 are acted on by the output signals of the amplifiers 29 to 32 respectively. Polarity reversing stages 39 to 44 are connected to the out-puts of the limit-value signalling devices 33 to 38 respectively so that pulse trains WTl to WT12 illustrated in Figure 9 are obtained, these pulse trains being 7t. apart and each pulse corresponding to a half-revolution of the preset vector. In addition, there are provided twelve AN~ gates 45 to 56 each of which is acted on, in the indicated manner, by two of the pulse trains WTl to WT12. Each of the gates 45 to 56 outputs a signal whenever the two pulse trains acting on it have a value different from 0. As can ~ ~
readily be deduced from Figure 9, there are thus set up at nutput terminal ~ ~ ;
57 to 62 of the angle switch 26 the control voltages which are denoted by Al ' , . ~ . , ~1~375S7 to A6 in Figure 3, whilst at the output terminals 63 to 68 the control volt- ~
ages denoted by Bl to B6 in Figure 3 are produced. - `
Figure 10 illustrates an alternative generator 71 for the formation of the frequency-synchronised sawtooth signal SZf. For this purpose the pulse trains WTl, WT3, WT5, WT7, WT9 and WTll and the output signals of the amplifiers 30 and 31 of the angle switch 26 are taken from the output term-inals 69 to 76 of the latter and applied to the correspondingly denoted in-put terminals of the sawtooth generator 77. The component voltage sin ~ ~' of the preset vector is connected to a further terminal. The pulse trains -~
WTl, WT3, WT7, WT9 and WTll are so combined in six AND gates 78 to 83 in the indicat0d manner .that the outputs of these AND gates successively supply, :
each during a period of T/6, actuating signals for six switches 84 to 89 which pass one of six sinusoidal voltages which are 60 apart in phase to ~`
the input of an amplifier 90.
Those portions of the six sinusoidal voltages which are passed by the ` switches 84 to 89 are illustrated in the voltage diagram of Figure 11. Each portion extends from -30 to +30 of the respective sinusoidal voltage. In this range, the sine function has an approximately linear form so that the generator 77 produces approximately the same frequency-synchronised sawtooth voltage form as is shown in Figure 6.
'` A third possible alternative form of a frequency-synchronised saw- ;`~
tooth generator is illustrated in Figure 12. This is based upon the idea of ;~
simulating, from four control voltages of the voltage control group employed ; ~ .
in pulsed operation, two phase currents iR and i9 of a stator current vector which in its rotation occupies six discrete positions which are, however, advanced by an angle of 30 in relation to the positions denoted by Ll to L6 in Figure 2. There are then formed from these phase currents, with due regard to the condition of symmetry iR + iS ~~ iT = ~ two orthogonal components of this simulated stator current vector, and the sine of the difference angle between the position of this vector and the angular position ~f the contin~
uously rotating preset vector is formed therefrom. The sine -12 ~`
... ... .
~ 37~7 ~ :
of this difference angle has a maximum negative value whenever the preset vector reaches any one of the ranges I to VI , always has the value 0 a~ ;
the middle of any of these ranges, and has a m~ximum positive value when the preset vector leaves any of these ranges. There are then obtained, through-out one rotation of the preset vector, voltage forms as illustrated in Figure 11 . -The phase currents iR and i~ are formed by means of two amplifiers 91 and 92, to the inputs of which there are applied the control voltages Al -~:
and A4, and A5 and A2, respectively. By means of a further amplifier 93 there is then formed that component i~ of the simulated stator current vector :
which falls in the direction denoted by L2 in Figure 2, while the other :. component i~ , orthogonal thereto, is assumed to descend in the direction of .~ the winding axis R of the rotating-field machine 1. By means of a vector rotator VD comprising two multipliers 94 and 9S and an amplifier 96, there ! is formed from the two orthogonal components i~ and iB of the simulated stator ~ current vector and the two components, also c\rthogonal, of the control voltage vector sin ~ and cos ~ *, a quantity corresponding to the sine of the angle ~ :
difference between the respective angular positions of these vectors, which quantity appears at the terminal 97 as sawtooth signal SZ~. There again ;~
appear here voltage forms of the kind illustrated in Figure 11. ~`
"' i/ ~,` ' ' -13_ ~ :
:
.
.
Claims (28)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An arrangement for producing, in a rotary-field electrical machine, a stator current vector having an effective position, between actual posit-ions, the arrangement comprising means for producing a stator current vector which can occupy alternately two adjacent actual positions at respective opposite sides of an effective position, and control means for controlling the durations for which the vector occupies said two adjacent actual positions thereby to control its effective position, the control means comprising a first signal generator for generating a first periodic signal synchronised with the frequency of the electrical machine stator current, second signal generator for generating a second periodic signal having a higher frequency than the first periodic signal, a comparator coupled to the first and second signal generators for comparing the values of the first and second periodic signals, and a change-over switch arranged to be control-led in dependence upon the comparator for switching the stator current vector between said two adjacent actual positions in dependence upon the relation-ship between the values of the first and second signals.
2. An arrangement according to claim 1, wherein the stator current vector producing means comprises an inverter including n controllable rectifier means having control inputs, said change-over switch being operable to vary control signals applied to said control inputs by a control signal generat-ing means which is part of said control means and is coupled to said control inputs.
3. An arrangement according to claim 2, wherein said control means com-prises a further control signal generating means, the two control signal generating means being such that the further control signal generating means will generate control signals which will lead the respective control signals generated by the first-mentioned control signal generating means by an angle .pi./n, and there being a change-over device for changing-over the connection of said control inputs from one to the other of the two control signal generating means in dependence upon the value of the frequency of the electrical machine stator current.
4. An arrangement according to claim 3, wherein the two control signal generating means share electrical circuitry to form a common angle switch.
5. An arrangement according to claim 3, wherein said change-over device comprises a threshold signalling circuit and a further change-over switch connected to be controlled by the threshold signalling circuit.
6. An arrangement according to claim 4, wherein said change-over device comprises a threshold signalling circuit and a further change-over switch connected to be controlled by the threshold signalling circuit.
7. An arrangement according to claim 2, 3 or 4 wherein the inverter is a three-phase bridge comprising as controllable rectifier means six thyristors, and the inverter further comprises six diodes connected in series with respective ones of the thyristors and capacitors interconnecting the thyristor anodes of the negative side of the bridge, and further capac-itors interconnecting the thyristor cathodes of the positive side of the bridge.
8. An arrangement according to claim 6, wherein the inverter is a three-phase bridge comprising as controllable rectifier means six thyristors, and the inverter further comprises six diodes connected in series with respect-ive ones of the thyristors and capacitors interconnecting the thyristor anodes of the negative side of the bridge, and further capacitors intercon-necting the thyristor cathodes of the positive side of the bridge.
9. An arrangement according to claim 2, 3 or 4 wherein the first-mention-ed control signal generating means comprises a voltage-to-frequency convertor and two n-stage ring counters arranged to be controlled by the voltage-to-frequency convertor.
10. An arrangement according to claim 5 or 6, wherein the first-mentioned control signal generating means comprises a voltage-to-frequency convertor and two n-stage ring counters arranged to be controlled by the voltage-to-frequency converter.
11. An arrangement according to claim 6 wherein the inventer is a three-phase bridge comprising as controllable rectifier means six thyristors, and the inverter further comprises six diodes connected in series with respect-ive ones of the thyristors and capacitors interconnecting the thyristor anodes of the negative side of the bridge, and further capacitors intercon-necting the thyristor cathodes of the positive side of the bridge, and wherein the first mentioned control signal generating means comprises a voltage-to frequency convertor and two-n-stage ring counters arranged to be controlled by the voltage-to-frequency converter.
12. An arrangement according to claim 1, 2 or 3 wherein the first and second signal generators are sawtooth generators.
13. An arrangement according to claim 4, 5 or 6 wherein the first and second signal generators are sawtooth generators.
14. An arrangement according to claim 11, wherein the first and second signal generators are sawtooth generators.
15. An arrangement according to claim 1, 2 or 3, wherein the first and second signal generators are sawtooth generators, and wherein the first signal generator comprises an integrator and means for applying to said integrator an input signal the polarity of which reverses periodically.
16. An arrangement according to claim 4,5 or 6, wherein the first and second signal generators are sawtooth generators, and wherein the first signal generator comprises an integrator and means for applying to said integrator an input signal the polarity of which reverses periodically.
17. An arrangement according to claim 11, wherein the first and second signal generators are sawtooth generators, and wherein the first signal generator comprises an integrator and means for applying to said integrator an input signal the polarity of which reverses periodically.
18. An arrangement according to claim 14, wherein said integrator is part of the voltage-to-frequency convertor.
19. An arrangement according to claim 2, 3 or 4, wherein the first-mentioned control signal generating means comprises an angle switch includ-ing inputs for components (sin .beta.* and cos .beta.*) of a control stator current vector and circuitry arranged for deriving from these components the control signals for the controllable rectifier means.
20. An arrangement according to claim 5 or 6, wherein the first-mentioned control signal generating means comprises an angle switch including inputs for components (sin .beta. * and cos .beta. * of a control stator current vector and circuitry arranged for deriving from these components the control signals for the controllable rectifier means.
21. An arrangement according to claim 2 wherein the first and second signal generators, are saw-tooth generators and wherein the first-mentioned control signal generating means comprises an angle switch including inputs for components (sin .beta. * and cos .beta. *) of a control stator current vector and circuitry arranged for deriving from these components the control signals for the controllable rectifier means.
22. An arrangement according to claim 21 wherein the first-mentioned control signal generating means comprises an angle switch including inputs for components (sin .beta. * and cos .beta. *) of a control stator current vector and circuitry arranged for deriving from these components the control signals for the controllable rectifier means, and wherein the first signal generator comprises an integrator and means for applying to said integrator an input signal the polarity of which reverses periodically.
23. An arrangement according to claim 4,wherein the first-mentioned con-trol signal generating means comprises an angle switch including inputs for components (sin .beta. * and cos .beta. *) of a control stator current vector and circuitry arranged for deriving from these components the control signals for the controllable rectifier means, and wherein said circuitry for acting on said components is the shared circuitry of the common angle switch and comprises six limit-value signallers two of which are connected by their in-puts directly to the input of the angle switch and the other four of which are connected by their inputs to said angle switch input via operational amplifi-ers, the six limit-value signallers having outputs connected directly and via polarity-reversing circuits of said common circuitry to twelve AND gates of said common circuitry, said common circuitry being so arranged that the control signals for the controllable rectifier means can be supplied by said twelve AND gates.
24. An arrangement according to claim 14, wherein said circuitry for acting on said components is the shared circuitry of the common angle switch and comprises six limit-value signallers two of which are connected by their inputs directly to the input of the angle switch and the other four of which are connected by their inputs to said angle switch input via operational amplifiers, the six limit-value signallers having outputs connected directly and via polarity-reversing circuits of said common circuitry to twelve AND
gates of said common circuitry, said common circuitry being so arranged that the control signals for the controllable rectifier means can be supplied by said twelve AND gates, and wherein said first signal generator comprises six switches and six AND gates arranged for controlling the six switches, the six switches being arranged for conducting selectively six respective sinusoidal signals which are .pi./3 apart and which are derived from component voltages sin .beta.* and cos .beta.* of a rotary preset control vector such that portions of the six sinusoidal signals form the sawtooth waveform.
gates of said common circuitry, said common circuitry being so arranged that the control signals for the controllable rectifier means can be supplied by said twelve AND gates, and wherein said first signal generator comprises six switches and six AND gates arranged for controlling the six switches, the six switches being arranged for conducting selectively six respective sinusoidal signals which are .pi./3 apart and which are derived from component voltages sin .beta.* and cos .beta.* of a rotary preset control vector such that portions of the six sinusoidal signals form the sawtooth waveform.
25. An arrangement according to claim 13, wherein inputs of said six AND
gates are coupled to the outputs of said four limited-value signallers.
gates are coupled to the outputs of said four limited-value signallers.
26. An arrangement according to claim 14, wherein said first signal generator comprises a component former for the simulation of orthogonal components of an imaginary stator current vector, the component former being arranged to receive four control signals from the first-mentioned control signal generating means and to produce two output quantities i.alpha. and i.beta. , the first signal generator also comprising a vector rotator having a first pair of inputs connected to receive the quantities i.alpha. and i.beta. , and a second pair of inputs available for receiving components of a rotary preset control vector.
27. An arrangement according to claim 21, wherein said first signal generator comprises a component former for the simulation of orthogonal components of an imaginary stator current vector, the component former being arranged to receive four control signals from the first-mentioned control signal generating means and to produce two output quantities i.alpha. and i.beta. , the first signal generator also comprising a vector rotator having a first pair of inputs connected to receive the quantities i.alpha. and i.beta. , and a second pair of inputs available for receiving components of a rotary preset control vector.
28. An arrangement according to claim 14, wherein said circuitry for acting on said components is the shared circuitry of the common angle switch, and comprises six limit-value signallers two of which are connected by their inputs directly to the input of the angle switch and the other four of which are connected by their inputs to said angle switch inputs via operational amplifiers, the six limit-value signallers having outputs connected directly and via polarity-reversing circuits of said common circuitry to twelve AND
gates of said common circuitry, said common circuitry being so arranged that the control signals for the controllable rectifier means can be supplied by said twelve AND gates, and wherein said first signal generator comprises a component former for the simulation of orthogonal components of an imaginary stator current vector, the component former being arranged to receive four control signals from the first-mentioned control signal generating means and to produce two output quantities i.alpha. and i.beta. , the first signal generator also comprising a vector rotator having a first pair of inputs connected to receive the quantities i.alpha. and i.beta. , and a second pair of inputs available for receiving components of a rotary preset control vector.
gates of said common circuitry, said common circuitry being so arranged that the control signals for the controllable rectifier means can be supplied by said twelve AND gates, and wherein said first signal generator comprises a component former for the simulation of orthogonal components of an imaginary stator current vector, the component former being arranged to receive four control signals from the first-mentioned control signal generating means and to produce two output quantities i.alpha. and i.beta. , the first signal generator also comprising a vector rotator having a first pair of inputs connected to receive the quantities i.alpha. and i.beta. , and a second pair of inputs available for receiving components of a rotary preset control vector.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2514557A DE2514557C3 (en) | 1975-04-03 | 1975-04-03 | Device for controlling the position of the stator current vector of a converter-fed induction machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1037557A true CA1037557A (en) | 1978-08-29 |
Family
ID=5943004
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA237,496A Expired CA1037557A (en) | 1975-04-03 | 1975-10-14 | Control of rotary-field electric machines |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS51122720A (en) |
| AT (1) | AT341046B (en) |
| BE (1) | BE832608R (en) |
| CA (1) | CA1037557A (en) |
| CH (1) | CH589968A5 (en) |
| DE (1) | DE2514557C3 (en) |
| FR (1) | FR2306564A2 (en) |
| GB (1) | GB1504605A (en) |
| SE (1) | SE410683B (en) |
| ZA (1) | ZA755222B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2704533C2 (en) * | 1977-02-03 | 1986-06-05 | Siemens AG, 1000 Berlin und 8000 München | Device for controlling the position of the stator current vector of a three-phase machine fed by a converter with controllable valves and with impressed intermediate circuit current |
| DE2726410A1 (en) | 1977-06-09 | 1978-12-21 | Licentia Gmbh | METHOD FOR DAMPING THE POLE WHEEL SUSPENSION OF ROTARY FIELD MACHINES |
| DE2750020A1 (en) * | 1977-11-05 | 1979-05-10 | Licentia Gmbh | AC-commutated static converter circuit - has diodes and circuit turning thyristor off independently of input voltage |
| DE2818933C2 (en) * | 1978-04-28 | 1982-06-16 | Siemens AG, 1000 Berlin und 8000 München | Control method for an asynchronous machine and circuit arrangement for carrying out the method |
| JPS6018198B2 (en) * | 1978-12-06 | 1985-05-09 | 株式会社東芝 | Inverter control device |
| DE2954430C2 (en) * | 1979-05-04 | 1986-10-30 | General Electric Co., Schenectady, N.Y. | Reversible static speed control device for an AC motor |
| DE2918083C2 (en) * | 1979-05-04 | 1986-09-18 | General Electric Co., Schenectady, N.Y. | Speed control device for an AC motor |
| DE3131361A1 (en) * | 1981-08-07 | 1983-02-24 | Siemens Ag | METHOD AND DEVICE FOR CONTROLLING THE LOAD CURRENT OF A POLE INVERTER |
| US4414609A (en) * | 1982-10-08 | 1983-11-08 | Sylvan R. Shemitz And Associates, Inc. | Luminaire for a visual display terminal |
| DE3280229D1 (en) | 1982-10-18 | 1990-09-20 | Elin Union Ag | METHOD FOR SETTING THE STATE FLOW VECTOR. |
| DE3411572C2 (en) * | 1984-03-29 | 1986-12-04 | Joetten, Robert, Prof.Dr.-Ing., 6100 Darmstadt | Method for regulating an asynchronous machine fed by a current-impressing intermediate circuit converter |
| CN114274581B (en) * | 2021-12-29 | 2022-09-30 | 金丰（中国）机械工业有限公司 | Electric energy management system of servo press |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT234221B (en) * | 1962-01-12 | 1964-06-25 | Licentia Gmbh | Arrangement for energy transfer |
| US3670235A (en) * | 1970-09-25 | 1972-06-13 | Borg Warner | Motor control system with compensation for low-frequency variations in motor energizing voltage |
| DE2236763C3 (en) * | 1972-07-26 | 1980-04-03 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Method and arrangement for controlling the position of the stator current vector of a three-phase machine fed by a converter with impressed intermediate circuit current |
-
1975
- 1975-04-03 DE DE2514557A patent/DE2514557C3/en not_active Expired
- 1975-07-11 AT AT536475A patent/AT341046B/en not_active IP Right Cessation
- 1975-08-01 GB GB32365/75A patent/GB1504605A/en not_active Expired
- 1975-08-13 ZA ZA00755222A patent/ZA755222B/en unknown
- 1975-08-21 BE BE159346A patent/BE832608R/en not_active IP Right Cessation
- 1975-10-14 CA CA237,496A patent/CA1037557A/en not_active Expired
-
1976
- 1976-02-03 FR FR7602964A patent/FR2306564A2/en active Granted
- 1976-02-09 SE SE7601371A patent/SE410683B/en not_active IP Right Cessation
- 1976-03-16 CH CH325076A patent/CH589968A5/xx not_active IP Right Cessation
- 1976-04-02 JP JP51037033A patent/JPS51122720A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| CH589968A5 (en) | 1977-07-29 |
| FR2306564A2 (en) | 1976-10-29 |
| DE2514557B2 (en) | 1977-03-10 |
| ZA755222B (en) | 1976-07-28 |
| ATA536475A (en) | 1977-05-15 |
| DE2514557A1 (en) | 1976-10-14 |
| GB1504605A (en) | 1978-03-22 |
| FR2306564B2 (en) | 1979-07-20 |
| SE7601371L (en) | 1976-10-04 |
| JPS562518B2 (en) | 1981-01-20 |
| BE832608R (en) | 1975-12-16 |
| AT341046B (en) | 1978-01-10 |
| DE2514557C3 (en) | 1981-09-24 |
| SE410683B (en) | 1979-10-22 |
| JPS51122720A (en) | 1976-10-27 |
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