CA1266089A - Method of adjustment of the electrical power in three phase systems and related three phase static voltage regulator - Google Patents
Method of adjustment of the electrical power in three phase systems and related three phase static voltage regulatorInfo
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- CA1266089A CA1266089A CA000479850A CA479850A CA1266089A CA 1266089 A CA1266089 A CA 1266089A CA 000479850 A CA000479850 A CA 000479850A CA 479850 A CA479850 A CA 479850A CA 1266089 A CA1266089 A CA 1266089A
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Abstract
ABSTRACT OF THE DISCLOSURE:
In a three phase static voltage regulator com-prising a set of parallel-connected thyristor and diode between each phase R, S and T of a three phase supply source and the corresponding phase of a three phase load, a pulse is produced in response to each single phase source voltage passing by a zero amplitude where the voltage amplitude changes from a negative to a positive value. A pulse is also produced in response to each such passage by a zero amplitude of the difference voltage between the phases R and S, which pulses are counted and digital-to-analog converted to produce a sawtooth signal of period To. During each period To, the sawtooth signal is compared with a reference signal to produce a control pulse. At the beginning of each control pulse, the pulses obtained from the difference voltage are applied to the gate of the thyristor interposed between the phase R and the corresponding phase of the load to turn the same on whereby a voltage is applied to the load. After the latter voltage is detected, the pulses obtained from the single phase voltage of each phase R, S and T are transmitted to the gate of the thyristor connected to this phase to turn the thyristors on and supply the load with power, until the control pulse ends. In operation, the electric power supplied to the three phase load is adjusted by adjusting the width of the control pulses through adjust-ment of the amplitude of the reference signal.
In a three phase static voltage regulator com-prising a set of parallel-connected thyristor and diode between each phase R, S and T of a three phase supply source and the corresponding phase of a three phase load, a pulse is produced in response to each single phase source voltage passing by a zero amplitude where the voltage amplitude changes from a negative to a positive value. A pulse is also produced in response to each such passage by a zero amplitude of the difference voltage between the phases R and S, which pulses are counted and digital-to-analog converted to produce a sawtooth signal of period To. During each period To, the sawtooth signal is compared with a reference signal to produce a control pulse. At the beginning of each control pulse, the pulses obtained from the difference voltage are applied to the gate of the thyristor interposed between the phase R and the corresponding phase of the load to turn the same on whereby a voltage is applied to the load. After the latter voltage is detected, the pulses obtained from the single phase voltage of each phase R, S and T are transmitted to the gate of the thyristor connected to this phase to turn the thyristors on and supply the load with power, until the control pulse ends. In operation, the electric power supplied to the three phase load is adjusted by adjusting the width of the control pulses through adjust-ment of the amplitude of the reference signal.
Description
12~8~
The present invention relates to a method and to a static, three phase voltage regulator for adjusting the electrical power supplied to a three phase load.
T~he subject invention is particularly suitable for use in automatic equipments for the adjustment of tem-perature and pressure or in electrical spot welding equip-ments.
Three phase static contactors are presently used to adjust the electrical power transmitted to a three phase load. In response to a control signal, the contactor connects the three phase load with the supply three phase voltage. Such a contactor presents the drawback of starting the load asynchronously, that is for a resistive load, the first half-cycle of the supply voltage transmitted to the load is not complete. This causes a high rate of variation of the load voltage with respect to time, which in some applicatnons, is not acceptable.
An object of the present invention is therefore to eliminate the above discussed drawback of the prior art contactorsby providing a method and a voltage regulator for adjusting the electrical power supplied to a three phase load which starts the latter load synchronously.
More specifically, in accordance with the in-vention, there is provided a method of adjusting the electric power supplied to a three phase load by an al-ternating, three phase source having first, second and third phases each supplying a single phase alternating voltage and being each connected to a corresponding one of the three phases of the load through an electronic switching unit with a gate electrode, said adjusting method comprising the steps of:
measuring the single phase voltage of the first, second and third phases of the alternating source;
producing first, second and third pulse signals -" ~
12~;60~
in response to the single phase voltage of said first, second and third phases, respectively, each pulse signal including a pulse produced upon each passage of the corresponding single phase voltage by a zero 5 amplitude where the voltage amplitude changes from .
a value of a first polarity to a value of a second polarity;
measuring an alternating, difference voltage between the first and second phases of the alternating source;
producing a fourth pulse signal in response to said measured difference voltage, said fourth pulse signal including a pulse produced upon each passage of the difference voltageby a zero amplitude where the vol-tage amplitude changes from a value of a first pola-rity to a value of a second polarity; ~ -generating, in response to the pulses of said fourth signal, a periodic sawtooth signal of period To and of increasing amplitude during each period To;
comparing, during each period To, the sawtooth signal with a re~e.ence signal of adjustable amplitude to produce a control pulse having a width varying with the amplitude of the reference signal;
transmitting, at the beginning of the- control pulse, the pulses of the fourth pulse signal to the gate electrode of a first one of said switching units inter-connecting one of the first and second phases of the source with the corresponding one of the three phases of the load, to turn said first switching unit on whereby a voltage is applied to the load; and detecting said voltage applied to the load, and upon detection of the voltage applied to the load, (a) interrupting transmission of the pulses of the fourth signal to the gate electrode of the first swit-. ~, .~ .
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ching unit, and (b) transmitting the pulses of the first pulse signal to the gate electrode of the switching unit interconnecting said first phase of the source with the corresponding phase of the load, the pulses of the second pulse signal to the gate electrode of the switching unit interconnecting said second phase of the source with the corresponding phase of the load, and the pulses of the third pulse signal to the gate electrode of the switching unit interconnecting said third phase of the source with the corresponding phase of the load, until the control pulse ends, whereby the switching units are turned on to supply electric power from the first, second and third phases of the source to the three phase load until said control pulse ends;
whereby, in operation, the electric power supplied to the three phase load is adjusted by adjust-ing the width of said control pulses through adjustment of the amplitude of said reference signal.
According to the invention, there is also pro-vided a static voltage regulator for adjusting the elec-tric power supplied to a three phase load by an alter-nating, three phase source having first, second and third phases each supplying a single phase alternating voltage and being each connected to a corresponding one of the three phases of the load through an electronic switching unit with a gate electrode, comprising:
means for measuring the single phase voltage of the first, second and third phases of the said alter-nating source;
means for producing first, second and third pulse signals in response to the single phase voltage of said first, second and third phases, respectively, each pulse signal including a pulse produced upon each passage of the corresponding single phase voltage by a ~P - 3 -~6~
zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second pola-rity;
means for measuring an alternating, difference voltage between the first and second phases of said alter-nating source;
means for producing a fourth pulse signal in response to said measured difference voltage, said fourth pulse signal including a pulse produced upon each passage of the differencevoltage by a zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second pola-rity;
means for generating, in response to the pulses of said fourth signal, a periodic sawtooth signal of period To and of increasing amplitude during each period To;
. means for producing a reference signal~of adjustable amplitude;
means for comparing, during each period To, the sawtooth signal with said reference signal to produce a control pulse having a width varying with the amplitude of the reference signal;
means for transmitting, at the beginning of said control pulse, the pulses of the fourth pulse signal to the gate electrode of a first one of said switching units interconnecting one of the first and second phases of the source with the corresponding one of the three phases of the load, to turn the first switching unit on whereby a voltage is applied to the load;
means for detecting said voltage applied to the load;
means responsive to said detection of the voltage applied to the load for interrupting transmission ~ t ~
of the pulses of the fourth signal to the gate electrode of the first switching unit; and means responsive to detection of the voltage applied to the load for transmitting the pulses of the first pulse signal to the gate electrode of the switching unit interconnecting the first phase of the source with the corresponding phase of the load, the pulses of the second pulse signal to the gate electrode of the switching unit interconnecting the second phase of the source with the corresponding phase of the load, and the pulses of the third pulse signal to the gate electrode of the switching unit interconnecting the third phase of the source with the corresponding phase of the load, until the control pulse ends, whereby the switching units are turned on to supply electric power from the first, second and third phases of the source to the three phase load until said control pulse ends;
whereby, in operation, the electric power supplied to the three phase load is adjusted by adjusting the width of said control pulses through adjustment of the amplitude of said reference signal.
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non restrictive description of a preferred embodiment thereof, given in conjuction with the accompanying drawings, in which:
Figure 1 is a schematic, block diagram of a three phase static voltage regulator in accordance with the present invention; and : 30 Figure 2 presents waveforms related to the operation of the voltage regulator of Figure 1.
As illustrated in Figure 1, the three phase static voltage regulator comprises (a) a thyristor 1 mounted in parallel with a diode 2 between a phase ~ of . ... ..... . ..
126~)89 a three phase, alternating supply source and a first phase 291 of a three phase load 29, (b) a thyristor 3 mounted in parallel with a diode 4 between a phase S of the supply source and a second phase 292 of the load 29, and (c) a thyristor 5 mounted in parallel with a diode 6 between the third phase T of the supply source and a third phase 293 of the three phase load 29. As can be noted, the thyristors 1, 3 and 5 conduct in directions opposite to that of their respective diodes 2, 4 and 6. In each case, the thyristor has its anode electrode and the diode its cathode electrode connected to the corresponding phase of the supply source.
A three phase transformer 7 measures the single phase, alternating voltage of each phase R, S and T of the source. The three so measured voltages are separa-tely amplified through amplifiers 8, 9 and 10, respectively, which amplifiers have a very high amplification gain.
When the amplitude of the single phase voltage of the phase R crosses zero, that is when this voltage passes by a zero amplitude where the voltage amplitude changes from a negative to a positive value, a monostable circuit 13 connected at the output of the amplifier 8 is triggered to produce a positive pulse of a duration suitable to turn the thyristor l on. Similarly when the amplitude of the single phase voltages of the phases S and T crosses zero, where the voltage amplitude changes from a positive to a negative value, the monostable circuits 12 and ll connected at the output of the amplifiers 9 and 10, respectively, are triggered to produce a positive pulse of the same duration as that produced by the monostable circuit 13, suitable to turn the thyristors 3 and 5 on.
The pulses from the monostable circuits 11, 12 and 13 are respectively supplied to a first input of AND gates 14~ 15 and 16. The pulses from the monostable ~, ...
0~9 circuits 13, 12 and 11 therefore turn the thyristors 1, 3 and 5 on synchronously, that is upon occurrence of the above defined zero crossings of the amplitude of the single phase voltages of the phases R, S and T, respectively, when transmitted to the gate electrodes of these thyristors.
A single phase transformer 17 measures the al-ternating voltage (voltage URs in Figure 2) between the phases R and S of the source. The so measured voltage is supplied to an amplifier 18 with a very high amplifi-cation gain. Upon each zero crossing of the measured voltage URs, that is when this alternating voltage passes by a zero amplitude where the voltage amplitude changes from a negative to a positive value, a monostable circuit l9 connected at the output of the amplifier 18 is triggered to produce a positive pulse having the same duration as the pulses from the monostable circuits 11, 12 and 13, that is suitable to turn the thyristor 1 on.
The pulses Ulg from the output of the monostable circuit 19 are illustrated by the curve a in Figure 2.
The pulses Ulg are counted by a 8-bit binary counter 20 generating a digital pulse count output signal converted into an analog signal by a 8-bit digital-to-analog converter 21.
A periodic sawtooth signal U21 of period To is produced at the output of the converter 21, which signal U21 has an amplitude which increases linearly from zero during each period To, for instance 3.56 seconds.
The sawtooth signal U21 is shown by curve _ in Figure 2.
The counter 20 is automatically reset after having counted a predetermined number of pulses, that is at the beginning of each period To. The period To therefore corresponds to a multiple of the period T of the single phase, alter-nating voltage of the phases R, S and T. The signal U
from the converter 21 is supplied to the inverting input ~Z66089 of a comparator 22 having a non inverting input supplied with a reference direct current voltage of adjustable ampli-tude produced by a direct current voltage through a poten-tiometer 23, During each period To, as long as the sawtooth voltage U21 has an amplitude lower than that of the reference vol-tage from the potentiometer 23, the output of the comparator produces a positive, control pulse U22 (curve c in Flgure
The present invention relates to a method and to a static, three phase voltage regulator for adjusting the electrical power supplied to a three phase load.
T~he subject invention is particularly suitable for use in automatic equipments for the adjustment of tem-perature and pressure or in electrical spot welding equip-ments.
Three phase static contactors are presently used to adjust the electrical power transmitted to a three phase load. In response to a control signal, the contactor connects the three phase load with the supply three phase voltage. Such a contactor presents the drawback of starting the load asynchronously, that is for a resistive load, the first half-cycle of the supply voltage transmitted to the load is not complete. This causes a high rate of variation of the load voltage with respect to time, which in some applicatnons, is not acceptable.
An object of the present invention is therefore to eliminate the above discussed drawback of the prior art contactorsby providing a method and a voltage regulator for adjusting the electrical power supplied to a three phase load which starts the latter load synchronously.
More specifically, in accordance with the in-vention, there is provided a method of adjusting the electric power supplied to a three phase load by an al-ternating, three phase source having first, second and third phases each supplying a single phase alternating voltage and being each connected to a corresponding one of the three phases of the load through an electronic switching unit with a gate electrode, said adjusting method comprising the steps of:
measuring the single phase voltage of the first, second and third phases of the alternating source;
producing first, second and third pulse signals -" ~
12~;60~
in response to the single phase voltage of said first, second and third phases, respectively, each pulse signal including a pulse produced upon each passage of the corresponding single phase voltage by a zero 5 amplitude where the voltage amplitude changes from .
a value of a first polarity to a value of a second polarity;
measuring an alternating, difference voltage between the first and second phases of the alternating source;
producing a fourth pulse signal in response to said measured difference voltage, said fourth pulse signal including a pulse produced upon each passage of the difference voltageby a zero amplitude where the vol-tage amplitude changes from a value of a first pola-rity to a value of a second polarity; ~ -generating, in response to the pulses of said fourth signal, a periodic sawtooth signal of period To and of increasing amplitude during each period To;
comparing, during each period To, the sawtooth signal with a re~e.ence signal of adjustable amplitude to produce a control pulse having a width varying with the amplitude of the reference signal;
transmitting, at the beginning of the- control pulse, the pulses of the fourth pulse signal to the gate electrode of a first one of said switching units inter-connecting one of the first and second phases of the source with the corresponding one of the three phases of the load, to turn said first switching unit on whereby a voltage is applied to the load; and detecting said voltage applied to the load, and upon detection of the voltage applied to the load, (a) interrupting transmission of the pulses of the fourth signal to the gate electrode of the first swit-. ~, .~ .
- ' ,' r -)8~
ching unit, and (b) transmitting the pulses of the first pulse signal to the gate electrode of the switching unit interconnecting said first phase of the source with the corresponding phase of the load, the pulses of the second pulse signal to the gate electrode of the switching unit interconnecting said second phase of the source with the corresponding phase of the load, and the pulses of the third pulse signal to the gate electrode of the switching unit interconnecting said third phase of the source with the corresponding phase of the load, until the control pulse ends, whereby the switching units are turned on to supply electric power from the first, second and third phases of the source to the three phase load until said control pulse ends;
whereby, in operation, the electric power supplied to the three phase load is adjusted by adjust-ing the width of said control pulses through adjustment of the amplitude of said reference signal.
According to the invention, there is also pro-vided a static voltage regulator for adjusting the elec-tric power supplied to a three phase load by an alter-nating, three phase source having first, second and third phases each supplying a single phase alternating voltage and being each connected to a corresponding one of the three phases of the load through an electronic switching unit with a gate electrode, comprising:
means for measuring the single phase voltage of the first, second and third phases of the said alter-nating source;
means for producing first, second and third pulse signals in response to the single phase voltage of said first, second and third phases, respectively, each pulse signal including a pulse produced upon each passage of the corresponding single phase voltage by a ~P - 3 -~6~
zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second pola-rity;
means for measuring an alternating, difference voltage between the first and second phases of said alter-nating source;
means for producing a fourth pulse signal in response to said measured difference voltage, said fourth pulse signal including a pulse produced upon each passage of the differencevoltage by a zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second pola-rity;
means for generating, in response to the pulses of said fourth signal, a periodic sawtooth signal of period To and of increasing amplitude during each period To;
. means for producing a reference signal~of adjustable amplitude;
means for comparing, during each period To, the sawtooth signal with said reference signal to produce a control pulse having a width varying with the amplitude of the reference signal;
means for transmitting, at the beginning of said control pulse, the pulses of the fourth pulse signal to the gate electrode of a first one of said switching units interconnecting one of the first and second phases of the source with the corresponding one of the three phases of the load, to turn the first switching unit on whereby a voltage is applied to the load;
means for detecting said voltage applied to the load;
means responsive to said detection of the voltage applied to the load for interrupting transmission ~ t ~
of the pulses of the fourth signal to the gate electrode of the first switching unit; and means responsive to detection of the voltage applied to the load for transmitting the pulses of the first pulse signal to the gate electrode of the switching unit interconnecting the first phase of the source with the corresponding phase of the load, the pulses of the second pulse signal to the gate electrode of the switching unit interconnecting the second phase of the source with the corresponding phase of the load, and the pulses of the third pulse signal to the gate electrode of the switching unit interconnecting the third phase of the source with the corresponding phase of the load, until the control pulse ends, whereby the switching units are turned on to supply electric power from the first, second and third phases of the source to the three phase load until said control pulse ends;
whereby, in operation, the electric power supplied to the three phase load is adjusted by adjusting the width of said control pulses through adjustment of the amplitude of said reference signal.
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non restrictive description of a preferred embodiment thereof, given in conjuction with the accompanying drawings, in which:
Figure 1 is a schematic, block diagram of a three phase static voltage regulator in accordance with the present invention; and : 30 Figure 2 presents waveforms related to the operation of the voltage regulator of Figure 1.
As illustrated in Figure 1, the three phase static voltage regulator comprises (a) a thyristor 1 mounted in parallel with a diode 2 between a phase ~ of . ... ..... . ..
126~)89 a three phase, alternating supply source and a first phase 291 of a three phase load 29, (b) a thyristor 3 mounted in parallel with a diode 4 between a phase S of the supply source and a second phase 292 of the load 29, and (c) a thyristor 5 mounted in parallel with a diode 6 between the third phase T of the supply source and a third phase 293 of the three phase load 29. As can be noted, the thyristors 1, 3 and 5 conduct in directions opposite to that of their respective diodes 2, 4 and 6. In each case, the thyristor has its anode electrode and the diode its cathode electrode connected to the corresponding phase of the supply source.
A three phase transformer 7 measures the single phase, alternating voltage of each phase R, S and T of the source. The three so measured voltages are separa-tely amplified through amplifiers 8, 9 and 10, respectively, which amplifiers have a very high amplification gain.
When the amplitude of the single phase voltage of the phase R crosses zero, that is when this voltage passes by a zero amplitude where the voltage amplitude changes from a negative to a positive value, a monostable circuit 13 connected at the output of the amplifier 8 is triggered to produce a positive pulse of a duration suitable to turn the thyristor l on. Similarly when the amplitude of the single phase voltages of the phases S and T crosses zero, where the voltage amplitude changes from a positive to a negative value, the monostable circuits 12 and ll connected at the output of the amplifiers 9 and 10, respectively, are triggered to produce a positive pulse of the same duration as that produced by the monostable circuit 13, suitable to turn the thyristors 3 and 5 on.
The pulses from the monostable circuits 11, 12 and 13 are respectively supplied to a first input of AND gates 14~ 15 and 16. The pulses from the monostable ~, ...
0~9 circuits 13, 12 and 11 therefore turn the thyristors 1, 3 and 5 on synchronously, that is upon occurrence of the above defined zero crossings of the amplitude of the single phase voltages of the phases R, S and T, respectively, when transmitted to the gate electrodes of these thyristors.
A single phase transformer 17 measures the al-ternating voltage (voltage URs in Figure 2) between the phases R and S of the source. The so measured voltage is supplied to an amplifier 18 with a very high amplifi-cation gain. Upon each zero crossing of the measured voltage URs, that is when this alternating voltage passes by a zero amplitude where the voltage amplitude changes from a negative to a positive value, a monostable circuit l9 connected at the output of the amplifier 18 is triggered to produce a positive pulse having the same duration as the pulses from the monostable circuits 11, 12 and 13, that is suitable to turn the thyristor 1 on.
The pulses Ulg from the output of the monostable circuit 19 are illustrated by the curve a in Figure 2.
The pulses Ulg are counted by a 8-bit binary counter 20 generating a digital pulse count output signal converted into an analog signal by a 8-bit digital-to-analog converter 21.
A periodic sawtooth signal U21 of period To is produced at the output of the converter 21, which signal U21 has an amplitude which increases linearly from zero during each period To, for instance 3.56 seconds.
The sawtooth signal U21 is shown by curve _ in Figure 2.
The counter 20 is automatically reset after having counted a predetermined number of pulses, that is at the beginning of each period To. The period To therefore corresponds to a multiple of the period T of the single phase, alter-nating voltage of the phases R, S and T. The signal U
from the converter 21 is supplied to the inverting input ~Z66089 of a comparator 22 having a non inverting input supplied with a reference direct current voltage of adjustable ampli-tude produced by a direct current voltage through a poten-tiometer 23, During each period To, as long as the sawtooth voltage U21 has an amplitude lower than that of the reference vol-tage from the potentiometer 23, the output of the comparator produces a positive, control pulse U22 (curve c in Flgure
2). The control pulses U22 from the output of the compa-rator 22 are supplied to a second input of the AND gates 14, 15 and 16 whereby,the pulses from the monostable circuits 13, 12 and 11 can be transmitted to the gate electrodes of the thyristors 1, 3 and 5, respectively, only when a pulse U~2 is generated, to turn these thyristors on. Of course, a control pulse U22 is produced only if a reference voltage is produced through the potentiometer 23, and the width g of the pulse U22 is adjusted through this potentiometer 23 by varying the amplitude of the reference voltage.
Each pulse transmitted to the thyristor 1 through the AND gate 16 is also supplied to an additional monostable circuit 24 which extends when necessary the width ~ of the control pulse U22 from the com~arator 22, to ensure supply of a pulse to the gate electrodes of the thyristors 3 and 5 through the AND gates 15 and 14 each time a pulse is supplied to the gate electrode of the thyristor 1. Accordingly, the thyristors 3 and 5 are always turned on following turning on of the thyristor 1, even if the non extended control pulse U22 from the comparator 22 ends just after transmission of a pulse to the gate electrode of the thyristor 1 or thyristor 3 through the gate I6 or 15. A same number of complete cycles of the single phase alternating voltages of the phases R, S and T of the supply source is accordingly supplied to the load 29 during each control pulse U22.
The three phase supply of the load 29 is accordingly balanced.
Any voltage applied to the load 26 is detected by a three phase transformer 30, and the so detected voltage is rectified through a three phase rectifier 31.
When no voltage applied to the load is detected, which corresponds to turning off of the thyristors 1, 3 and S, a threshold circuit 32, connected to the output of the rectifier 31 supplying on its output a low logic level signal. In response to the latter signal, an inverter 26 generates a high logic level signal.
When no voltage is detected by the transformer 30, the low logic level signal at the output of the thre-shold circuit 32 is supplied to a third input of the AND gates 14, 15 and 16 to prevent transmission of the pulses from the monostable circuits 13, 12 and 11 to the gate electrodes of the thyristors 1, 3 and 5, respectively.
Another AND gate 25 has a first input supplied with the pulses Ulg from the monostable circuit 19, a second input supplied with the pulses U22 from the compa-rator 22, and a third input supplied with the output si-gnal of the inverter 26. When no voltage is applied to the three phase load 29 and when a control pulse U22 from the comparator 22 is supplied to the second input of the AND gate 25 having its third input 3 supplied with a high logic level signal from the inverter 26 as no voltage is applied to the load, the pulses Ulg from the monostable circuit 19 are transmitted to the gate of the thyristor 1 through the AND gate 25, a pulse amplifier 27 and a pulse transformer 28 to turn the thyristor 1 on.
The thyristor 1 and the diode 4 then : conduct and a voltage is applied to the load 29, which voltage is detected through the transformer 30 and rectified by the rectifier 31. me output of the threshold ~L26~39 circuit 32 accordingly supplies a high logic level signal applied to the third input of the AND gates 14, 15 and 16, and to the input of the inverter 26 which then supplies a low logic level signal to the third input of the gate 25 to prevent this gate 25 to transmit the pulses from the monostable circuit 19 to the pulse amplifier 27.
As a high logic level signal is supplied by the threshold circuit 32 to the third input of the gates 14, 15 and 16 and the control pulse from the comparator 22 is supplied to the second inpu-t of these three AND gates, the pulses from the monostable circuit 13 are supplied to the gate electrode of the thyristor 1 through the gate 16, the pulse amplifier 27, and the pulse transformer 2~ to turn the thyristor 1 on, the pulses from the monostable circuit 12 are supplied to the gate of the thyris-tor 3 through the AND
gate 15, a pulse ampli:Eier 34 and a pulse transformer 36 to turn the thyristor 3 on, and the pulses from the monostable circuit 11 are supplied to the gate electrode of the thyristor 5 through the AND gate 14, a pulse amplifier 33 and a pulse transformer 35 to turn -the thyristor 5 on, and that until the control pulse U22 from the comparator 22 having its width ~ eventually extended by the monostable circuit 24 ends, as explained hereinabove. When the input c of each pulse amplifier 33, 34 and 27 is connected to ground, the control pulses of positive polarity from the input a of the pulse amplifier 33 or 34, or the input a or b of the pulse amplifier 27 determine the successive switching of the corresponding output of each pulse amplifier, and the pulses are transmitted to the secondary of the corresponding pulse transformers 35, 36 and 28.
When the inpu-t c of each pulse amplifier 33, 34 and 27 is connected to a positive potential with respect to the ground, the pulses from the inputs a and b are not transmi-tted, as a consequence of i-t, in the secondary of the ' corresponding pulse transformers 35, 36 and 28 there is no pulse.
This procedure is repeated for each of the successive period T (see Figure 2) of the periodic sawtooth voltage signal U21.
Accordingly, the number of cycles of the single phase voltages of each phase R, S, T of the supply source transmitted to the load 29 during each successive, basic time period T of the sawtooth signal V2~1 is adjusted by varying the width ~ of the pulses U22 of Figure 2, through adjustment of the level of the reference voltage produced through the potentiometer 23, which reference voltage is - lOa -` ~--compared with the amplitude of the sawtooth voltage U
of Figure 2 by the comparator 22.
The above described switching procedure provides for turning on of the thyristors 1, 3 and 5 synchronously with the zero crossings of the alternating voltages of the corresponding phases R, S and T, except for the short period at the beginning of each pulse U22 during which the pulses from the monostable circuit 19 are transmitted to the gate of the thyristor 1 through the AND gate 25, the pulse ampliier 27, and the pulse transformer 28.
Two current transformers 37 and 38 detect any overcurrent supplied to the three phase load 29. In response to sùch an overcurrent detection, a threshold circuit 39 supplies a control input of the pulse ampli-fiers 27, 34 and 33 with a pulse transmission interrup-tion signal to block any pulses to the gate of the thy-ristors 1, 3 and 5. Protection of the load 29 against overcurrent is thereby obtained.
The three phase static voltage regulator pre-sents in particular the following two advantages:
- it ensures supply of each phase of the load 29 with the same number of complete cycles of alternating voltage; and - variation in the amplitude of the source single phase voltages does not influence the number of complete cycles of alternating voltage supplied to the load.
Although the present invention has been des-cribed hereinabove by way of a preferred embodiment thereof, it should be pointed out that any modification to this preferred embodiment, within the scope of the appended claims, is not deemed to change or alter the nature and scope of the subject invention.
Each pulse transmitted to the thyristor 1 through the AND gate 16 is also supplied to an additional monostable circuit 24 which extends when necessary the width ~ of the control pulse U22 from the com~arator 22, to ensure supply of a pulse to the gate electrodes of the thyristors 3 and 5 through the AND gates 15 and 14 each time a pulse is supplied to the gate electrode of the thyristor 1. Accordingly, the thyristors 3 and 5 are always turned on following turning on of the thyristor 1, even if the non extended control pulse U22 from the comparator 22 ends just after transmission of a pulse to the gate electrode of the thyristor 1 or thyristor 3 through the gate I6 or 15. A same number of complete cycles of the single phase alternating voltages of the phases R, S and T of the supply source is accordingly supplied to the load 29 during each control pulse U22.
The three phase supply of the load 29 is accordingly balanced.
Any voltage applied to the load 26 is detected by a three phase transformer 30, and the so detected voltage is rectified through a three phase rectifier 31.
When no voltage applied to the load is detected, which corresponds to turning off of the thyristors 1, 3 and S, a threshold circuit 32, connected to the output of the rectifier 31 supplying on its output a low logic level signal. In response to the latter signal, an inverter 26 generates a high logic level signal.
When no voltage is detected by the transformer 30, the low logic level signal at the output of the thre-shold circuit 32 is supplied to a third input of the AND gates 14, 15 and 16 to prevent transmission of the pulses from the monostable circuits 13, 12 and 11 to the gate electrodes of the thyristors 1, 3 and 5, respectively.
Another AND gate 25 has a first input supplied with the pulses Ulg from the monostable circuit 19, a second input supplied with the pulses U22 from the compa-rator 22, and a third input supplied with the output si-gnal of the inverter 26. When no voltage is applied to the three phase load 29 and when a control pulse U22 from the comparator 22 is supplied to the second input of the AND gate 25 having its third input 3 supplied with a high logic level signal from the inverter 26 as no voltage is applied to the load, the pulses Ulg from the monostable circuit 19 are transmitted to the gate of the thyristor 1 through the AND gate 25, a pulse amplifier 27 and a pulse transformer 28 to turn the thyristor 1 on.
The thyristor 1 and the diode 4 then : conduct and a voltage is applied to the load 29, which voltage is detected through the transformer 30 and rectified by the rectifier 31. me output of the threshold ~L26~39 circuit 32 accordingly supplies a high logic level signal applied to the third input of the AND gates 14, 15 and 16, and to the input of the inverter 26 which then supplies a low logic level signal to the third input of the gate 25 to prevent this gate 25 to transmit the pulses from the monostable circuit 19 to the pulse amplifier 27.
As a high logic level signal is supplied by the threshold circuit 32 to the third input of the gates 14, 15 and 16 and the control pulse from the comparator 22 is supplied to the second inpu-t of these three AND gates, the pulses from the monostable circuit 13 are supplied to the gate electrode of the thyristor 1 through the gate 16, the pulse amplifier 27, and the pulse transformer 2~ to turn the thyristor 1 on, the pulses from the monostable circuit 12 are supplied to the gate of the thyris-tor 3 through the AND
gate 15, a pulse ampli:Eier 34 and a pulse transformer 36 to turn the thyristor 3 on, and the pulses from the monostable circuit 11 are supplied to the gate electrode of the thyristor 5 through the AND gate 14, a pulse amplifier 33 and a pulse transformer 35 to turn -the thyristor 5 on, and that until the control pulse U22 from the comparator 22 having its width ~ eventually extended by the monostable circuit 24 ends, as explained hereinabove. When the input c of each pulse amplifier 33, 34 and 27 is connected to ground, the control pulses of positive polarity from the input a of the pulse amplifier 33 or 34, or the input a or b of the pulse amplifier 27 determine the successive switching of the corresponding output of each pulse amplifier, and the pulses are transmitted to the secondary of the corresponding pulse transformers 35, 36 and 28.
When the inpu-t c of each pulse amplifier 33, 34 and 27 is connected to a positive potential with respect to the ground, the pulses from the inputs a and b are not transmi-tted, as a consequence of i-t, in the secondary of the ' corresponding pulse transformers 35, 36 and 28 there is no pulse.
This procedure is repeated for each of the successive period T (see Figure 2) of the periodic sawtooth voltage signal U21.
Accordingly, the number of cycles of the single phase voltages of each phase R, S, T of the supply source transmitted to the load 29 during each successive, basic time period T of the sawtooth signal V2~1 is adjusted by varying the width ~ of the pulses U22 of Figure 2, through adjustment of the level of the reference voltage produced through the potentiometer 23, which reference voltage is - lOa -` ~--compared with the amplitude of the sawtooth voltage U
of Figure 2 by the comparator 22.
The above described switching procedure provides for turning on of the thyristors 1, 3 and 5 synchronously with the zero crossings of the alternating voltages of the corresponding phases R, S and T, except for the short period at the beginning of each pulse U22 during which the pulses from the monostable circuit 19 are transmitted to the gate of the thyristor 1 through the AND gate 25, the pulse ampliier 27, and the pulse transformer 28.
Two current transformers 37 and 38 detect any overcurrent supplied to the three phase load 29. In response to sùch an overcurrent detection, a threshold circuit 39 supplies a control input of the pulse ampli-fiers 27, 34 and 33 with a pulse transmission interrup-tion signal to block any pulses to the gate of the thy-ristors 1, 3 and 5. Protection of the load 29 against overcurrent is thereby obtained.
The three phase static voltage regulator pre-sents in particular the following two advantages:
- it ensures supply of each phase of the load 29 with the same number of complete cycles of alternating voltage; and - variation in the amplitude of the source single phase voltages does not influence the number of complete cycles of alternating voltage supplied to the load.
Although the present invention has been des-cribed hereinabove by way of a preferred embodiment thereof, it should be pointed out that any modification to this preferred embodiment, within the scope of the appended claims, is not deemed to change or alter the nature and scope of the subject invention.
Claims (20)
1. A method of adjusting the electric power supplied to a three phase load by an alternating, three phase source having first, second and third phases each supplying a single phase alternating voltage and being each connected to a corresponding one of the three phases of the load through an electronic switching unit with a gate electrode, said adjusting method comprising the steps of:
measuring the single phase voltage of the first, second and third phases of the alternating source;
producing first, second and third pulse signals in response to the single phase voltage of said first, second and third phases, respectively, each pulse signal including a pulse produced upon each passage of the corresponding single phase voltage by a zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second polarity;
measuring an alternating, difference voltage between the first and second phases of the alternating source;
producing a fourth pulse signal in response to said measured difference voltage, said fourth pulse signal including a pulse produced upon each passage of the difference voltage by a zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second polarity;
generating, in response to the pulses of said fourth signal, a periodic sawtooth signal of period To and of increasing amplitude during each period To;
comparing, during each period To, the sawtooth signal with a reference signal of adjustable amplitude to produce a control pulse having a width varying with the amplitude of the reference signal;
transmitting, at the beginning of said control pulse, the pulses of the fourth pulse signal to the gate electrode of a first one of said switching units inter-connecting one of the first and second phases of the source with the corresponding one of the three phases of the load, to turn said first switching unit on whereby a voltage is applied to the load; and detecting said voltage applied to the load, and upon detection of the voltage applied to the load, (a) interrupting transmission of the pulses of the fourth signal to the gate electrode of the first swit-ching unit, and (b) transmitting the pulses of the first pulse signal to the gate electrode of the switching unit interconnecting said first phase of the source with the corresponding phase of the load, the pulses of the second pulse signal to the gate electrode of the switching unit interconnecting said second phase of the source with the corresponding phase of the load, and the pulses of the third pulse signal to the gate electrode of the switching unit interconnecting said third phase of the source with the corresponding phase of the load, until the control pulse ends, whereby the switching units are turned on to supply electric power from the first, second and third phases of the source to the three phase load until said control pulse ends;
whereby, in operation, the electric power supplied to the three phase load is adjusted by adjust-ing the width of said control pulses through adjustment of the amplitude of said reference signal.
measuring the single phase voltage of the first, second and third phases of the alternating source;
producing first, second and third pulse signals in response to the single phase voltage of said first, second and third phases, respectively, each pulse signal including a pulse produced upon each passage of the corresponding single phase voltage by a zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second polarity;
measuring an alternating, difference voltage between the first and second phases of the alternating source;
producing a fourth pulse signal in response to said measured difference voltage, said fourth pulse signal including a pulse produced upon each passage of the difference voltage by a zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second polarity;
generating, in response to the pulses of said fourth signal, a periodic sawtooth signal of period To and of increasing amplitude during each period To;
comparing, during each period To, the sawtooth signal with a reference signal of adjustable amplitude to produce a control pulse having a width varying with the amplitude of the reference signal;
transmitting, at the beginning of said control pulse, the pulses of the fourth pulse signal to the gate electrode of a first one of said switching units inter-connecting one of the first and second phases of the source with the corresponding one of the three phases of the load, to turn said first switching unit on whereby a voltage is applied to the load; and detecting said voltage applied to the load, and upon detection of the voltage applied to the load, (a) interrupting transmission of the pulses of the fourth signal to the gate electrode of the first swit-ching unit, and (b) transmitting the pulses of the first pulse signal to the gate electrode of the switching unit interconnecting said first phase of the source with the corresponding phase of the load, the pulses of the second pulse signal to the gate electrode of the switching unit interconnecting said second phase of the source with the corresponding phase of the load, and the pulses of the third pulse signal to the gate electrode of the switching unit interconnecting said third phase of the source with the corresponding phase of the load, until the control pulse ends, whereby the switching units are turned on to supply electric power from the first, second and third phases of the source to the three phase load until said control pulse ends;
whereby, in operation, the electric power supplied to the three phase load is adjusted by adjust-ing the width of said control pulses through adjustment of the amplitude of said reference signal.
2. The method of claim 1, wherein the width of each control pulse starts at the beginning of the corresponding period To and ends when the amplitude of the sawtooth signal reaches that of the reference signal.
3. The method of claim 1 or 2, wherein during each period To, the amplitude of the sawtooth signal in-creases linearly from a zero amplitude.
4. The method of claim 1 or 2, further compri-sing the step of prolonging each control pulse so that a same number of cycles of the single phase voltages of the first, second and third phases is transmitted to the respective phases of the load.
5. The method of claim 1, wherein said sawtooth signal generating step comprises the steps of:
counting the pulses of said fourth signal during each period To to produce a digital pulse count signal;
and converting said digital count signal into an analog signal constituting said sawtooth signal.
counting the pulses of said fourth signal during each period To to produce a digital pulse count signal;
and converting said digital count signal into an analog signal constituting said sawtooth signal.
6. The method of claim 1 or 5, in which said reference signal is produced from a direct current voltage by means of a potentiometer through which the amplitude of the reference signal is adjustable.
7. The method of claim 1, further comprising the steps of:
detecting an overcurrent supplied to the load by the said alternating source; and interrupting transmission of the pulses of the first, second, third and fourth pulse signals to the gate electrodes of the switching units upon said detection of overcurrent.
detecting an overcurrent supplied to the load by the said alternating source; and interrupting transmission of the pulses of the first, second, third and fourth pulse signals to the gate electrodes of the switching units upon said detection of overcurrent.
8. The method of claim 1, in which the single phase alternating voltage of each of said first,second, and third phases of the source has a period T, the said period To being a multiple of the period T.
9. A static voltage regulator for adjusting the electric power supplied to a three phase load by an alternating, three phase source having first, second and third phases each supplying a single phase alternating vol-tage and being each connected to a corresponding one of the three phases of the load through an electronic switching unit with a gate electrode, comprising:
means for measuring the single phase voltage of the first, second and third phases of the said alter-nating source;
means for producing first, second and third pulse signals in response to the single phase voltage of said first, second and third phases, respectively, each pulse signal including a pulse produced upon each passage of the corresponding single phase voltage by a zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second polarity;
means for measuring an alternating, difference voltage between the first and second phases of said alter-nating source;
means for producing a fourth pulse signal in response to said measured difference voltage, said fourth pulse signal including a pulse produced upon each passage of the difference voltage by a zero amplitude where the vol-tage amplitude changes from a value of a first polarity to a value of a second polarity;
means for generating, in response to the pulses of said fourth signal, a periodic sawtooth signal of period To and of increasing amplitude during each period To;
means for producing a reference signal of adjustable amplitude;
means for comparing, during each period To, the sawtooth signal with said reference signal to produce a control pulse having a width varying with the amplitude of the reference signal;
means for transmitting, at the beginning of said control pulse, the pulses of the fourth pulse signal to the gate electrode of a first one of said switching units inter-connecting one of the first and second phases of the source with the corresponding one of the three phases of the load, to turn the first switching unit on whereby a voltage is applied to the load;
means for detecting said voltage applied to the load;
means responsive to said detection of the voltage applied to the load for interrupting transmission of the pulses of the fourth signal to the gate electrode of the first switching unit; and means responsive to detection of the voltage applied to the load for transmitting the pulses of the first pulse signal to the gate electrode of the switching unit interconnecting the first phase of the source with the corresponding phase of the load, the pulses of the second pulse signal to the gate electrode of the switching unit interconnecting the second phase of the source with the corresponding phase of the load, and the pulses of the third pulse signal to the gate electrode of the switching unit interconnecting the third phase of the source with the corresponding phase of the load, until the control pulse ends, whereby the switching units are turned on to supply electric power from the first, second and third phases of the source to the three phase load until said control pulse ends;
whereby, in operation, the electric power supplied to the three phase load is adjusted by adjusting the width of said control pulses through adjustment of the amplitude of said reference signal.
means for measuring the single phase voltage of the first, second and third phases of the said alter-nating source;
means for producing first, second and third pulse signals in response to the single phase voltage of said first, second and third phases, respectively, each pulse signal including a pulse produced upon each passage of the corresponding single phase voltage by a zero amplitude where the voltage amplitude changes from a value of a first polarity to a value of a second polarity;
means for measuring an alternating, difference voltage between the first and second phases of said alter-nating source;
means for producing a fourth pulse signal in response to said measured difference voltage, said fourth pulse signal including a pulse produced upon each passage of the difference voltage by a zero amplitude where the vol-tage amplitude changes from a value of a first polarity to a value of a second polarity;
means for generating, in response to the pulses of said fourth signal, a periodic sawtooth signal of period To and of increasing amplitude during each period To;
means for producing a reference signal of adjustable amplitude;
means for comparing, during each period To, the sawtooth signal with said reference signal to produce a control pulse having a width varying with the amplitude of the reference signal;
means for transmitting, at the beginning of said control pulse, the pulses of the fourth pulse signal to the gate electrode of a first one of said switching units inter-connecting one of the first and second phases of the source with the corresponding one of the three phases of the load, to turn the first switching unit on whereby a voltage is applied to the load;
means for detecting said voltage applied to the load;
means responsive to said detection of the voltage applied to the load for interrupting transmission of the pulses of the fourth signal to the gate electrode of the first switching unit; and means responsive to detection of the voltage applied to the load for transmitting the pulses of the first pulse signal to the gate electrode of the switching unit interconnecting the first phase of the source with the corresponding phase of the load, the pulses of the second pulse signal to the gate electrode of the switching unit interconnecting the second phase of the source with the corresponding phase of the load, and the pulses of the third pulse signal to the gate electrode of the switching unit interconnecting the third phase of the source with the corresponding phase of the load, until the control pulse ends, whereby the switching units are turned on to supply electric power from the first, second and third phases of the source to the three phase load until said control pulse ends;
whereby, in operation, the electric power supplied to the three phase load is adjusted by adjusting the width of said control pulses through adjustment of the amplitude of said reference signal.
10. The voltage regulator of claim 9, in which each of said electronic switching units comprises a thyristor having said gate electrode and connected in parallel with a diode, said thyristor having an anode electrode connected to a cathode electrode of said diode also having an anode electrode connected to a cathode electrode of the thyristor.
11. The voltage regulator of claim 9, wherein said sawtooth signal generating means comprises:
a counter for counting the pulses of the fourth pulse signal during each time period To and for supplying a digital pulse count signal; and a digital-to-analog converter for converting said digital count signal into an analog signal constituting said sawtooth signal.
a counter for counting the pulses of the fourth pulse signal during each time period To and for supplying a digital pulse count signal; and a digital-to-analog converter for converting said digital count signal into an analog signal constituting said sawtooth signal.
12. The voltage regulator of claim 9 or 11, wherein said fourth pulse signal producing means comprises a monostable circuit for producing the pulses of said fourth signal in response to said measured difference voltage.
13. The voltage regulator of claim 11, wherein said comparing means comprises a comparator having a first input supplied with the analog signal from said digital-to-analog converter, a second input supplied with the refe-rence signal and an output for supplying said control pulses.
14. The voltage regulator fo claim 9 or 13, wherein said reference signal producing means comprises a potentiometer supplied with a direct current voltage for producing the said reference signal of adjustable ampli-tude.
15. The voltage regulator of claim 11, wherein the single phase alternating voltage of each of said first, second and third phases of the source has a period T, and wherein the said period To is a multiple of the period T.
16. The voltage regulator of claim 9, further comprising means for prolonging each of said control pulses so that a same number of cycles of the single phase voltages of said first, second and third phases are transmitted to the corresponding ones of the three phases of the load during said control pulses.
17. The voltage regulator of claim 13, further comprising a monostable circuit with an input receiving the pulses of one of the first, second and third pulse signals transmitted to the gate electrode of the corresponding switching unit during said control pulses, and an output connected to the output of the said comparator, in order to prolong each of said control pulses so that a same number of cycles of the single phase voltages of said first, second and third phases are transmitted to the corresponding ones of the three phases of the load during said control pulses.
18. The voltage regulator of claim 9,10 or 16,wherein said means for detecting the voltage applied to the load comprises (a) a threshold circuit responsive to the detected voltage applied to the load for producing a digital pulse transmission control signal, and (b) an inverter for inverting said pulse transmission control signal, wherein said fourth signal pulses transmitting means and said fourth signal pulses transmission interrupting means comprise a first AND gate having a first input supplied with the pulses of the fourth signal, a second input supplied with said control pulses, a third input supplied with said inverted pulse transmission control signal, and an output connected to the gate electrode of the said first switching unit, and wherein said means for transmitting the pulses of the first, second and third pulse signals to the gate electrodes of the respective switching units comprises for each of said first, second and third pulse signals a second AND gate having a first input supplied with the pulses of the corresponding one of the first, second, and third pulse signals, a second input supplied with the control pulses, a third input supplied with the said pulse transmis-sion control signal, and an output connected to the gate electrode of the corresponding switching unit.
19. The voltage regulator of claim 1, further comprising means for detecting an overcurrent supplied to the said load and for interrupting transmission of any pulse to the gate electrodes of the said electronic switching units in response to said overcurrent detection.
20. The voltage regulator of claim 19, wherein said pulses of the first, second, third and fourth pulse signals are transmitted to the gate electrodes of the switching units through pulse amplifiers each having a control input, and wherein said overcurrent detecting and transmission interrupting means comprises a threshold cir-cuit for producing, in response to said overcurrent detection, an interruption signal supplied to the control inputs of the different pulse amplifiers for thereby interrupting trans-mission of any pulse to the gate electrodes of the said electronic switching units.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| RO114363A RO86933B1 (en) | 1984-04-24 | 1984-04-24 | Method for the control of electric power in three-phase systems and static three-phase power control regulator |
| RO114363 | 1984-04-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1266089A true CA1266089A (en) | 1990-02-20 |
Family
ID=20114804
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000479850A Expired CA1266089A (en) | 1984-04-24 | 1985-04-23 | Method of adjustment of the electrical power in three phase systems and related three phase static voltage regulator |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1266089A (en) |
| RO (1) | RO86933B1 (en) |
| SU (1) | SU1468430A3 (en) |
-
1984
- 1984-04-24 RO RO114363A patent/RO86933B1/en unknown
-
1985
- 1985-04-23 CA CA000479850A patent/CA1266089A/en not_active Expired
- 1985-04-24 SU SU853884947A patent/SU1468430A3/en active
Also Published As
| Publication number | Publication date |
|---|---|
| SU1468430A3 (en) | 1989-03-23 |
| RO86933B1 (en) | 2002-06-28 |
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