Solid state current source polyphase inverter induction motor drive
OwnerRobert L. Risberginventor
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Abstract
A solid state, current source, polyphase inverter induction motor drive is disclosed wherein the current source is derived from a constant potential buss. Each side of the buss is connected to the inverter via a separate chopper. The choppers normally operate in unison to supply a controlled current to the inverter. Each time the inverter sequence is to be advanced, the chopper current is reduced to zero on the side of the inverter, either positive or negative, that requires a commutation. Chopper current is then reinstigated and feeds the next set of inverter thyristors in the inverter sequence. Alternative means for rendering the current source non-inductive during inverter commutations, and transformerless means for providing motor voltages well above rated voltage are also disclosed.
Claims11
A solid state current source, polyphase inverter induction motor drive comprising:
- a. a constant potential D.C. buss including a positive buss and a negative buss;
- b. a polyphase inverter comprising a plurality of thyristor switches supplied from said constant potential D.C. buss and providing polyphase driving current at its output;
- c. clamp means including a plurality of clamp diodes connected to the output of said polyphase inverter;
- and
- d. controlled current D.C. chopper means interposed between each side of said D.C. buss and said polyphase inverter for controlling the magnitude of current fed from said D.C. buss to said polyphase inverter and for interrupting the current flow to each side of said polyphase inverter for a period of time sufficient to permit said inverter thyristor switches to assume their blocking state prior to refiring a new set of inverter thyristor switches and thereby commutate current from one inverter switch of one phase to an adjacent switch in another phase, said polyphase inverter serving as a steering means for the controlled D.C. current and said chopper means operating to re-establish the desired magnitude of current following a starvation period that insures turn-off of the prior conducting inverter switches, said polyphase inverter being directly commutated only by said chopper.
A solid state current source, polyphase inverter induction motor drive comprising:
- a. a constant potential D.C. buss including a positive buss and a negative buss;
- b. a self-commutating polyphase inverter comprising a plurality of thyristor switches supplied from said constant potential D.C. buss and providing polyphase driving current at its output, adjacent ones of said plurality of thyristor switches being capacitively coupled;
- c. clamp means including a plurality of clamp diodes connected to the output of said self-commutating polyphase inverter;
- d. first chopper means including a first inductive coil, a first electronic switch connected from said positive buss to one end of said first inductive coil, the other end of which is connected to the common anode side of said self-commutating polyphase inverter, and a first discharge path means for permitting said first inductive coil to continue to supply current to said self-commutating polyphase inverter even when said first electronic switch is in the off state;
- e. second chopper means including a second inductive coil, a second electronic switch connected from said negative buss to one end of said second inductive coil, the other end of which is connected to the common cathode side of said self-commutating polyphase inverter, and a second discharge path means for permitting said second inductive coil to continue to supply current to said self-commutating polyphase inverter even when said second electronic switch is in the off state, said first and second electronic switches switching in unison for varying the ratio of time said first and second inductive coils are connected to said positive and negative buss, respectively, or freewheeling via said first and second discharge paths, respectively.
Dependencies are inferred from the claim text.