Reactive power processing circuit for a current source GTO invertor

• US 4,721,897 A
• Filed: 01/21/1987
• Issued: 01/26/1988
• Est. Priority Date: 01/24/1986
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Meidensha (Meidensha Corporation)
• Original Assignee: Kabushiki Kaisha Meidensha (Meidensha Corporation)
• Inventors: Kubota, Hisao, Matsuse, Koki
• Primary Examiner(s): BEHA JR, WILLIAM
• Application Number:
  US07/005,646
• Time in Patent Office: 370 Days
• Field of Search: 363/37, 363/58, 363/137, 318/762, 318/803, 318/767
• US Class Current: 318/767
• CPC Class Codes: H02J 3/1892 the arrangements being an integral part of the load, e.g. a motor, or of its control circuit
• CPC Class Codes: H02M 7/5152 with separate extinguishing means
• CPC Class Codes: H02P 2201/03 AC-DC converter stage controlled to provide a defined DC link voltage
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence

Abstract

A reactive power processing circuit for a current source GTO invertor in which a reactive current generated from a load of the GTO invertor is rectified by means of a fly wheel circuit and is sent to a capacitor so as to store a commutation surge voltage generated whenever a commutation of the invertor occurs, an excessive charge voltage across the capacitor is regenerated to a direct current output side of a power rectifier, and a pair of GTO (Gate Turn Off Thyristors) thyristors are connected between the capacitor and the direct current output side of the power rectifier in their forward directions so as to carry out a discharge operation for the excessive charge voltage across the capacitor. Consequently, with the number of circuit elements remarkably reduced, the reactive power processing at times of a high-frequency operation and acceleration/deceleration (variable speed) operation of the invertor can be achieved.

Claims

1. A reactive power processing circuit for a current source invertor, comprising:

(a) a power rectifier which carries out a gate phase control of a plurality of switching elements to convert an alternating current derived from an alternating current source into a corresponding direct current;

(b) a smoothing circuit having at least one direct current reactor for smoothing the direct current derived from the power rectifier so as to produce a smoothed direct current;

(c) an invertor main circuit having a plurality of bridge-connected gate turn off thyristors (GTO thyristors) for inverting the direct current derived from the smoothing circuit into an alternating current and for deriving a load with the alternating current at output sides thereof;

(d) a fly wheel circuit having a plurality of bridge-connected diodes whose alternating current sides are connected to the corresponding output sides of the invertor main circuit, for rectifying a reactive current derived from the load;

(e) a capacitor, connected across a direct current side of the fly wheel circuit, for storing a commutation surge voltage generated in the load;

(f) a pair of GTO thyristors, connected to the capacitor in their forward directions, for operatively discharging a charge across the capacitor toard positive and negative poles of the power rectifier; and

(g) a control circuit for triggering the pair of GTO thyristors to discharge the excessive charge across the capacitor and for continuing to send triggering pulses to the switching elements of the power rectifier for an interval required for a power rectifying operation of the power rectifier so that the switching elements are retriggered when a discharge operation of the pair of GTO thyristors is completed.

2. The reactive power processing circuit as set forth in claim 1, wherein the load is a three-phase induction motor having a reactance.

3. The reactive power processing circuit as set forth in claim 1, wherein the switching elements in the power rectifier comprise reverse blocked triode thyristors.