EP0029250A2
Expired / Lapsed
EP
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Bank selection in naturally commutated thyristor controlled static power converters
Assignee: Westinghouse Electric Corp
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Filing: 1980-11-18
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Granted: —
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Expires: 2000-11-18
Abstract
Abstract A static converter for generating and supplying to a load an eletrical output waveform of a desired frequency from a multiphase AC voltage source, uses naturally commutated thyristors arranged in positive and negative banks which are sequentially fired in a manner as to avoid circulating currents. The nonload carrying bank is instantly identified, and, firing pulses to the thyristors in the nonload carrying bank are inhibited only after the current therethrough actually goes to zero. Where the thyristors are arranged in pulse groups, the firing pulses to each group are inhibited separately and in some instances not all groups in the nonload carrying bank are inhibited. Termination of current flow through a thyristor group is determined by comparing the group output voltage with a composite signal representative of the intended group voltage which is generated by summing selected portions of the source voltages applied to the group. Further firing of the thyristors in the group is inhibited only after the difference between these two signals exceeds a preset threshold value for an interval at least equal in duration to the thyristor reverse recovery time.
Inventors
- 👤 Eric John Stacey
- 👤 Donal Eugene Baker
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 22:01
CPC Classifications
H; H02; H02M; H02M5/00; H02M5/02; H02M5/04; H02M5/22; H02M5/25; H02M5/27; H02M5/271
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
113 words
A method of generating a synthesized electrical output waveform of a desired frequency from a multiphase AC voltage source using two banks of thyristors, comprising the steps of: generating firing pulses to sequentially fire a plurality of thyristors arranged in positive and negative banks of a naturally commutated power circuit inserted between the AC voltage source and a load to generate a desired output waveform which is applied to said load; determining which thyristor bank is carrying the load; determining when the current in the nonload carrying thyristor bank actually goes to zero; inhibiting the application of firing pulses to thyristors in the nonload carrying bank when the current therethrough goes to zero.
Claim 2
Independent Claim
113 words
A method of generating a synthesized electrical output waveform of a desired frequency from a multiphase AC voltage source using two banks of thyristors, comprising the steps of: generating firing pulses to sequentially fire a plurality of thyristors arranged in positive and negative banks of a naturally commutated power circuit inserted between the AC voltage source and a load to generate a desired output waveform which is applied to said load; determining which thyristor bank is carrying the load; determining when the current in the nonload carrying thyristor bank actually goes to zero; inhibiting the application of firing pulses to thyristors in the nonload carrying bank when the current therethrough goes to zero.
Claim 3
Dependent Claim
61 words
The method of claim 1 including the step of arranging the thyristors in each thyristor bank in groups interconnected by interphase transformers, and including a step of determining when the current through one of said thyristor groups in the nonload carrying bank goes to zero and inhibiting the firing pulses to said one group when the current therethrough goes to zero.
Claim 4
Dependent Claim
46 words
The method of claim 2 including a step of separately determining when the current through each thyristor group in the nonload carrying bank goes to zero and inhibiting the firing pulses to each group in the nonload carrying bank when the current therethrough goes to zero.
Claim 5
Dependent Claim
91 words
The method of claim 2 or 3 wherein the step of determining when current through a nonload carrying thyristor group goes to zero comprises the steps of generating a composite signal representative of the intended group output voltage by summing selected portions of the input phase voltages applied to the thyristor group and comparing said composite signal with the thyristor group output voltage, the method characterized by inhibiting firing pulses to the thyristors in the group when said composite signal and said thyristor group output voltage differ by a preset amount.
Claim 6
Dependent Claim
46 words
The method of claim 4 wherein the firing pulses to the group are inhibited only when the difference between the composite signal and the thyristor group output voltage exceeds said predetermined amount for an interval at least equal in duration to the thyristor reverse recovery time.
Claim 7
Dependent Claim
120 words
A converter apparatus for generating an electrical output waveform of a desired frequency to be applied to a load, from a multiphase AC voltage source, said converter comprising: a naturally commutated power circuit including a plurality of thyristors arranged in positive and negative banks inserted between the AC voltage source and the load; control means for firing said thyristors sequentially to generate said desired output waveform which is applied to said load; means for determining which thyristor bank is carrying the load current; zero current determining means for determining when the current in the nonload current carrying bank goes to zero; and means for inhibiting the firing of thyristors in nonload current carrying bank in response to zero current therethrough.
Claim 8
Dependent Claim
120 words
A converter apparatus for generating an electrical output waveform of a desired frequency to be applied to a load, from a multiphase AC voltage source, said converter comprising: a naturally commutated power circuit including a plurality of thyristors arranged in positive and negative banks inserted between the AC voltage source and the load; control means for firing said thyristors sequentially to generate said desired output waveform which is applied to said load; means for determining which thyristor bank is carrying the load current; zero current determining means for determining when the current in the nonload current carrying bank goes to zero; and means for inhibiting the firing of thyristors in nonload current carrying bank in response to zero current therethrough.
Claim 9
Dependent Claim
62 words
The converter of claim 6 wherein the thyristors in each thyristor bank are arranged in pulse groups interconnected by interphase transformers and including means for determining when the current in one of said thyristor groups in the nonload carrying bank goes to zero, and means for inhibiting firing of the thyristors in said one group only in response to zero current therethrough.
Claim 10
Dependent Claim
102 words
The converter of claim 7 wherein the means for determining the instant of zero current through a thyristor group in the nonload carrying group includes means for generating a composite signal representative of the intended group output voltage by summing selected portions of the source phase voltages applied to said thyristor group and means for comparing said composite signal with the thyristor group output voltage and for generating an inhibit signal when the composite signal and the group output voltage differ by a predetermined amount, said means for inhibiting firing of the thyristors in the group being responsive to said inhibit signal.
Claim 11
Dependent Claim
74 words
The converter of claim 8 wherein said means for generating said composite signal comprises a separate switch connected to each of the source voltages applied to the thyristor group with the outputs of all of said switches connected together and means responsive to said control means for closing said switches individually when the control means fires the associated thyristor and for maintaining the switch closed until the next thyristor in the group is fired.
Claim 12
Dependent Claim
47 words
The converter of claim 8 including means for delaying generation of said inhibit signal until said difference between the composite signal and said thyristor group output voltage exceeds said predetermined amount for an interval equal in duration at least to the reverse recovery time of the thyristors.
Claim 13
Dependent Claim
47 words
The converter of claim 7 or 10 including means for separately determining when the current in each thyristor group in the nonload carrying bank goes to zero and means for separately inhibiting firing of the thyristors in each such group in response to zero current there- thrcugh.
Claim 14
Dependent Claim
48 words
The converter of claim 11 wherein there are two thyristor groups in the nonload carrying bank and the means for separately inhibiting firing of the thyristors in each nonload carrying group includes means which preclude inhibiting firing pulses to both nonload carrying thyristor groups at the same time.
Claim 15
Dependent Claim
45 words
The converter of claim 6 or 7 including means for activating said inhibiting means and means responsive to said control means for preventing operation . of said activating means at instants when said control means attempt to fire a thyristor in the nonload carrying bank.
Claim 16
Dependent Claim
41 words
The converter of claim 7 including means for activating said inhibiting means and means responsive to said control means for preventing operation of said activating means at instants when said control means attept to fire a thyristor in said one group.
Claim 17
Dependent Claim
142 words
The converter of claim 6, comprising: a separate control switch connected to each phase of the AC source voltage applied to said group of power switches; means for closing each control switch individually when the power switch connected to the associated source phase voltage is turned on and for turning off said control switch when the next power switch in the group is switched on; means for summing the voltages produced at the outputs of said group of control switches to form a composite signal, wherein said zero current determining means includes means for comparing said composite signal with the output voltage of said group of power switches and for generating an output signal indicating that the current through the group of power switches has gone to zero when said composite signal and the group output voltage differ by a predetermined amount.
Claim 18
Dependent Claim
34 words
The converter of claim 15 including means for delaying generation of said output signal until said difference between the composite signal and the group output voltage reaches said predetermined amount for a preselected interval.
References Cited (Backward Citations)
No citation records indexed.
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