Short circuit protection means for power circuits

Abstract

Abstract A SOLID STATE POWER CIRCUIT, SUCH AS A POLYPHASE INVERTER OF ENERGIZING AN A-C MOTOR IN AN A-C ADJUSTABLE SPEED DRIVE SYSTEM, INCLUDES TWO OR MORE PARALLEL CONNECTED SERIES CIRCUITS EACH INCLUDING A PAIR OF ALTERNATELY CONDUCTIVE THYRISTORS IN SERIES INDICTIVE MEANS AND A FILTER NETWORK INCLUDING AT LEAST TWO L-C STAGES FOR SUPPLYING D-C ELECTRIC POWER TO THE SERIES CIRCUITS FROM A SOURCE OF ELECTRIC POTENTIAL. WHEN A SHORT CIRCUIT OR SHOOTTHROUGH IN THE POWER CIRCUIT HAS OCCURRED OR, UNDER SOME CONDITIONS, IS ABOUT TO OCCUR, THE RESULTING HIGH CURRENT FLOW TO THE SERIES CIRCUITS FROM THE FILTER NETWORK IS DETECTED AND ALL OF THE THYRISTORS OF AT LEAST TWO OF THE SERIES CIRCUITS ARE TURNED ON SIMULTANEOUSLY IN RESPONSE TO THE DETECTED CURRENT SUCH THAT THE FILTER CAPACITOR OF THE L-C STAGE ADJACENT THE SERIES CIRCUITS WILL RESONATE WITH THE TOTAL EFFECTIVE PARALLEL INDUCTANCE IN THE SERIES CIRCUITS TO PROVIDE SUFFICIENT REVERSE VOLTAGE TO TURN OFF ALL OF THE TYRISTORS. TO RESPOND TO INCREASED CURRENT FLOW RESULTING FROM A WIDE RANGE OF FAULT CONDITIONS IN AN EFFECTIVE AND ECONOMICAL MANNER, THE DETECTION MEANS IS RESPONSIVE TO THE CAPACITIVE CURRENT FLOW IN AT LEAST TWO OF THE L-C STAGES INCLUDING THE TWO STAGES ADJACENT THE SERIES CIRCUITS. A DIODE OR SIMILAR RECITIFER IS PROVIDED ACROSS THE FILTER INDUCTOR OF THE L-C STAGE ADJACENT THE SERIES CIRCUITS TO PREVENT EXCESSIVE VOLTAGE ON THE RESONATING CAPACITOR, TO CONTROL RIPLE VOLTAGE, AND TO PREVENT UNDAMPED OSCILLATIONS IN THE FILTER NETWORK D R A W I N G

Inventors

• 👤 E Skogsholm

Bibliographic Details