GB1585666A - Variable frequency electrical inverters - Google Patents
Variable frequency electrical inverters Download PDFInfo
- Publication number
- GB1585666A GB1585666A GB35773/77A GB3577377A GB1585666A GB 1585666 A GB1585666 A GB 1585666A GB 35773/77 A GB35773/77 A GB 35773/77A GB 3577377 A GB3577377 A GB 3577377A GB 1585666 A GB1585666 A GB 1585666A
- Authority
- GB
- United Kingdom
- Prior art keywords
- inverter
- counter
- store
- pulse
- frequency
- 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
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M7/525—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with automatic control of output waveform or frequency
- H02M7/527—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with automatic control of output waveform or frequency by pulse width modulation
- H02M7/529—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with automatic control of output waveform or frequency by pulse width modulation using digital control
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M7/5152—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with separate extinguishing means
- H02M7/5155—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with separate extinguishing means wherein each commutation element has its own extinguishing means
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M7/525—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with automatic control of output waveform or frequency
- H02M7/527—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with automatic control of output waveform or frequency by pulse width modulation
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
- Control Of Multiple Motors (AREA)
Description
(54) IMPROVEMENTS IN
VARIABLE FREQUENCY ELECTRICAL INVERTERS
(71) We, ATELIERS DE CONSTRUC
TIONS ELECTRIQUES DE CHARLEROI (ACEC) of 54 Chaussee de Charleroi, Saint Gillies,
Brussels, Belgium, a body corporate organized according to the laws of Belgium, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
The present invention relates to electrical inverters and in particular to a variable frequency electrical inverter which has a plurality of thyristors provided with control electrodes and is controlled by a control chain supplying a command signal for the frequency of the invertor.
It is an object of the invention to provide an inverter, and in particular its logical control system which, for any frequency in a very wide range of operating frequencies, supplies throughout that range of frequencies a voltage of determined form in relation to the electrical angles and having either a minimum of harmonic components or a complete lack of certain particularly troublesome harmonic components.
According to the present invention there is provided a variable frequency electrical inverter having a plurality of thyristors provided with control electrodes, which is controlled by a control chain supplying a command signal to a pulse generator of variable frequency establishing the frequency of the inverter, the pulses supplied by the pulse generator having a frequency higher than the desired frequency of the inverter, said inverter including: a counter receiving the output pulses from the pulse generator, said counter being reset to zero after every n pulses wherein n is a preselected positive integar at least equal to 12; and a read-only store, the stages of the counter acting as addresses for the store, whereby in succession and in cyclic order during each period of the operating frequency of the inverter, n groups of predetermined control signals are fed from the read-only store to the control electrode of the thyristors of the inverter in the same cyclic order.
The present invention will now be described in greater detail by way of example with reference to the accompanying drawing, wherein:
Figure 1 is a block diagram of one preferred form of an electrical inverter and its logical control system;
Figure 2 is a waveform showing the evolution of a control voltage during one period of the operating frequency.
Referring to Figure 1, a three-phase electrical inverter comprises six main thyristors 1 to 6, each having a diode associated therewith, and, eight thyristors 7 to 14 constituting an extinction circuit. The number of thyristors in the extinction circuit is not critcal and may be reduced to three if desired. From a D.C. voltage network +U, -U this inverter feeds three busbars R,S and T of an A.C. voltage network, which may, for example, be used to drive an asynchronous motor M. The speed of this motor M is controlled by a control chain (not shown) supplying an analogue speed instructio between two terminals 15. The two terminals 15 are the input terminals of an analogue-todigital converter 16. The converter 16 has a plurality of outputs at which appear the primary states of a number corresponding to the digital value of the analogue signal applied to the input 15. The outputs of the converter 16 are applied to the input of an address selector of a read-only store 17. In the store 17 are stored a whole series of closely spaced values of times corresponding to the different times between two fronts of successive pulses supplied by a pulse generator 18, thus making it possible to produce pulses at a whole series of different rates of closely values. These times are for example a series of 3800 values between 200 and 4000 microseconds, the differences between two neighbouring times of the series being one microsecond. In this case the rates ol the pulse generator vary between 5000 Hz and 250 Hz, and they correspond to a series of 3800 frequency between 13.8 Hz and 0.694
Hz multiplied by a number n (=360), from which the converter 16 may select the suitable value for a frequency instruction supplied through the address selector of the store 17.
The difference between two neighbouring times of the above series of times can be determined by the time between the fronts of two or more successive pulses of master quartz oscillator 19. The pulses leaving this master
oscillator 19 are applied to the input of a
counter 20. The states of the different stages of
this counter 20 are applied to one of the two
series of inputs of a comparator 21, the other
series of inputs of this comparator 21 being connected by means of a locking device 22 to
the outputs of the read-only store 17 deter
mining the rate of the pulse generator 18. The
locking device 22 makes it possible to fix the
state of the inputs of the comparator 21 at a
predetermined moment for effecting the com
parison between the two series of inputs of the
comparator 21. When the counter 20 reaches
the number determined by the inputs locked
by the device 22 the comparator supplies a
pulse to a monostable circuit 23, which also
forms a part of the generator 18. At the out
put of the monostable circuit 23 a pulse then
appears which is of sufficiently long duration
to permit the unlocking of the device 22 and
the application of the state of the output
stages of the store 17 to the input of the
comparator 21. This same pulse passing from
the monostable circuit 23 resets the counter
20 to zero and constitutes the output pulse
of the pulse generator 18. As already stated,
the rate of the output pulse amounts to n
times the frequencyfof the inverter. The
number n is preferably selected to be equal
to 360, but obviously may be much greater if
accuracy has to be increased, for example
n = 3600. On the other hand, whenn = 12 or
smaller the desired effect can no longer be
achieved.
The output signal of the generator 18 is
applied to a cyclic switch having n positions,
n being in this instance equal to 360. This
switch is composed of a nine-stage binary
counter 24 associated with a detector 25 for
the number 260, which acts as zeroizing signal
transmitter for the counter 24. This counter
24 counts the n equal angular subdivisions of
each period of each operating frequency of the
inverter. The stages of the counter 24 serve as
an address for a read-only store 26 and, in
succession and in a cyclic order which is passed
through completely during each period of
each operating frequency, select the n sets of instructions preestablished for the different
thyristors 1 to 14 of the inverter and stored
in the store 26 for transmission, by way of
suitable amplifiers (not shown), to the gates
of the thyristors 1 to 14.
The selection of the instructions preestablished for the different thyristors is identical,
except for constant phase displacement, for
all the main thyristors 1 to 6 and is effected, not in dependence on time, but in depend
ence on the electrical degrees of a period of unspecified length, corresponding to a frequency taken from the range of operating frequencies. This selection is made in accordance with the well known Fourier analysis method in order to eliminate or minimize one or more harmonic components. Because these instructions are established in dependence on electrical degrees, if a certain shape of the control wave, such as the control wave shown in Figure 2, minimizes certain harmonic components for an operating frequency of the range, it also minimizes these harmonic components for all the other operating frequencies.
If for the different frequencies in the range of operating frequencies the most troublesome harmonic components are not always the same, it is possible to provide two or more stores 26, counters 24, and detectors 25 each eliminating a different set of harmonic components. In this case, the switching of the output pulse of the generator 18 to a first set or to a second, third, etc. set can then be effected by means of a switch arranged at the output of the monostable circuit 23 and operated by one or more frequency instruction detectors 28 connected to the outputs of the store 17.
If the above described inverter is used with a motor whose slots are not parallel to the axis of the rotor, but offset by a certain angle in relation to the direction of the axis, it is possible to select this angle of offset at a value such as to make it possible to eliminate a pair of harmonics which are not eliminated by the selection of the control wave. Conversely, if the selection of the offset angle of the slots makes it possible to eliminate a certain pair of harmonics, it is possible to select a control wave shape permitting the addition or elimination of other harmonics.
In the above example the rate of the pulse generator 18 is controlled by a digital instruction. There are obviously other simpler pulse generators, but these do not have the stability of a quartz oscillator whose rate is controlled directly by an analogue input voltage. These generators are known under the name VCO (voltage control oscillator); they do not need a converter 16 and the inputs 15 then constitutes directly the input of the pulse generator. The output of a VCO pulse generator is treated in the same manner as the output of the generator 18 and is applied to a cyclic detector 24 of the read-only memory 26.
WHAT WE CLAIM IS:
1. A variable frequency electrical inverter having a plurality of thyristors provided with control electrodes, which is controlled by a control chain supplying a command signal to a pulse generator of variable frequency establishing the frequency of the inverter, the pulses supplied by the pulse generator having a frequency higher than the desired frequency of the inverter, said inverter including: a counter receiving the output pulses from the pulse generator, said counter being reset to zero after every n pulses wherein n is a preselected positive integer at least equal to 12; and a readonly store, the stages of the counter acting as addresses for the store, whereby in succession and in cyclic order during each period of the operating frequency of the inverter, n groups
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (3)
- **WARNING** start of CLMS field may overlap end of DESC **.oscillator 19 are applied to the input of a counter 20. The states of the different stages of this counter 20 are applied to one of the two series of inputs of a comparator 21, the other series of inputs of this comparator 21 being connected by means of a locking device 22 to the outputs of the read-only store 17 deter mining the rate of the pulse generator 18. The locking device 22 makes it possible to fix the state of the inputs of the comparator 21 at a predetermined moment for effecting the com parison between the two series of inputs of the comparator 21. When the counter 20 reaches the number determined by the inputs locked by the device 22 the comparator supplies a pulse to a monostable circuit 23, which also forms a part of the generator 18. At the out put of the monostable circuit 23 a pulse then appears which is of sufficiently long duration to permit the unlocking of the device 22 and the application of the state of the output stages of the store 17 to the input of the comparator 21. This same pulse passing from the monostable circuit 23 resets the counter20 to zero and constitutes the output pulse of the pulse generator 18. As already stated, the rate of the output pulse amounts to n times the frequencyfof the inverter. The number n is preferably selected to be equal to 360, but obviously may be much greater if accuracy has to be increased, for example n = 3600. On the other hand, whenn = 12 or smaller the desired effect can no longer be achieved.The output signal of the generator 18 is applied to a cyclic switch having n positions, n being in this instance equal to 360. This switch is composed of a nine-stage binary counter 24 associated with a detector 25 for the number 260, which acts as zeroizing signal transmitter for the counter 24. This counter24 counts the n equal angular subdivisions of each period of each operating frequency of the inverter. The stages of the counter 24 serve as an address for a read-only store 26 and, in succession and in a cyclic order which is passed through completely during each period of each operating frequency, select the n sets of instructions preestablished for the different thyristors 1 to 14 of the inverter and stored in the store 26 for transmission, by way of suitable amplifiers (not shown), to the gates of the thyristors 1 to 14.The selection of the instructions preestablished for the different thyristors is identical, except for constant phase displacement, for all the main thyristors 1 to 6 and is effected, not in dependence on time, but in depend ence on the electrical degrees of a period of unspecified length, corresponding to a frequency taken from the range of operating frequencies. This selection is made in accordance with the well known Fourier analysis method in order to eliminate or minimize one or more harmonic components. Because these instructions are established in dependence on electrical degrees, if a certain shape of the control wave, such as the control wave shown in Figure 2, minimizes certain harmonic components for an operating frequency of the range, it also minimizes these harmonic components for all the other operating frequencies.If for the different frequencies in the range of operating frequencies the most troublesome harmonic components are not always the same, it is possible to provide two or more stores 26, counters 24, and detectors 25 each eliminating a different set of harmonic components. In this case, the switching of the output pulse of the generator 18 to a first set or to a second, third, etc. set can then be effected by means of a switch arranged at the output of the monostable circuit 23 and operated by one or more frequency instruction detectors 28 connected to the outputs of the store 17.If the above described inverter is used with a motor whose slots are not parallel to the axis of the rotor, but offset by a certain angle in relation to the direction of the axis, it is possible to select this angle of offset at a value such as to make it possible to eliminate a pair of harmonics which are not eliminated by the selection of the control wave. Conversely, if the selection of the offset angle of the slots makes it possible to eliminate a certain pair of harmonics, it is possible to select a control wave shape permitting the addition or elimination of other harmonics.In the above example the rate of the pulse generator 18 is controlled by a digital instruction. There are obviously other simpler pulse generators, but these do not have the stability of a quartz oscillator whose rate is controlled directly by an analogue input voltage. These generators are known under the name VCO (voltage control oscillator); they do not need a converter 16 and the inputs 15 then constitutes directly the input of the pulse generator. The output of a VCO pulse generator is treated in the same manner as the output of the generator 18 and is applied to a cyclic detector 24 of the read-only memory 26.WHAT WE CLAIM IS: 1. A variable frequency electrical inverter having a plurality of thyristors provided with control electrodes, which is controlled by a control chain supplying a command signal to a pulse generator of variable frequency establishing the frequency of the inverter, the pulses supplied by the pulse generator having a frequency higher than the desired frequency of the inverter, said inverter including: a counter receiving the output pulses from the pulse generator, said counter being reset to zero after every n pulses wherein n is a preselected positive integer at least equal to 12; and a readonly store, the stages of the counter acting as addresses for the store, whereby in succession and in cyclic order during each period of the operating frequency of the inverter, n groupsof predetermined control signals are fed from the read-only store to the control electrodes of the thyristors of the inverter in the same cyclic order.
- 2. An inverter according to claim 1, wherein values pre-established in the read-only store are selected in order to eliminate harmonic components which are not eliminated by angular offsetting, in relation to the direction of the axis of the rotor, of the slots of an asynchronous motor supplied by the inverter.
- 3. A variable frequency electrical inverter constructed substantially as herein described with reference to and as illustrated in the accompanying drawing.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
BE1007589A BE845644A (en) | 1976-08-27 | 1976-08-27 | INVERTER |
Publications (1)
Publication Number | Publication Date |
---|---|
GB1585666A true GB1585666A (en) | 1981-03-11 |
Family
ID=3862848
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB35773/77A Expired GB1585666A (en) | 1976-08-27 | 1977-08-25 | Variable frequency electrical inverters |
Country Status (6)
Country | Link |
---|---|
BE (1) | BE845644A (en) |
DE (1) | DE2738645A1 (en) |
FR (1) | FR2363222A1 (en) |
GB (1) | GB1585666A (en) |
IT (1) | IT1079946B (en) |
NL (1) | NL7709439A (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4245290A (en) * | 1978-12-18 | 1981-01-13 | United Technologies Corporation | Sliding notch pulse width modulation (PWM) |
DE3006924A1 (en) * | 1980-02-25 | 1981-09-10 | Walter Dittel GmbH, 8910 Landsberg | Lightweight three=phase inverter - has transformer with three chopper stages with flip=flops controlling reference and delay flip=flops |
US4348734A (en) * | 1980-07-10 | 1982-09-07 | Reliance Electric Company | Converter by stored switching pattern |
-
1976
- 1976-08-27 BE BE1007589A patent/BE845644A/en not_active IP Right Cessation
- 1976-11-05 FR FR7633369A patent/FR2363222A1/en active Granted
-
1977
- 1977-08-25 GB GB35773/77A patent/GB1585666A/en not_active Expired
- 1977-08-25 IT IT50781/77A patent/IT1079946B/en active
- 1977-08-26 NL NL7709439A patent/NL7709439A/en unknown
- 1977-08-26 DE DE19772738645 patent/DE2738645A1/en not_active Ceased
Also Published As
Publication number | Publication date |
---|---|
FR2363222B1 (en) | 1981-12-04 |
DE2738645A1 (en) | 1978-03-02 |
BE845644A (en) | 1977-02-28 |
IT1079946B (en) | 1985-05-13 |
NL7709439A (en) | 1978-03-01 |
FR2363222A1 (en) | 1978-03-24 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PS | Patent sealed | ||
PCNP | Patent ceased through non-payment of renewal fee |