Switch=off circuitry for discharge of inverter branch pairs - consists of two gate-controlled semiconductor switches arranged between poles of DC voltage source

摘要

Two free-wheeling diodes (D1, D2) are respectively connected in antiparallel with semiconductor switches (T1, T2), and in series with a linear choke coil (LK1, LK2) limiting the current rise upon switching on. A series circuit of a switch-off discharge capacitor (CS1, CS2) and a switch-off discharge diode (DS1, DS2) is connected in parallel to the semiconductor switch, with a connection direct to their junction point. A common storage capacitor (CO) is assigned, each terminal being connected to one pole of the DC source (Ud) via an ohmic resistance (RO1, RO2), and making contact at the intersection point between the switch off discharge diode and capacitor of the respective series circuits. The terminal of the two switch off discharge capacitors not lying at the AC voltage terminal is connected directly to the storage capacitor (CO), and the size of the ohmic resistances (RO1, RO2) and the storage capacitor (CO) is satisfied by the condition: K.(RO1 + RO2).CO is less than Te,min, where K is greater or equal to 2 or less than or equal to 4. Te,min is the smallest conducting time of the semiconducting switches. ADVANTAGE - Cost of components reduced due to additional diodes.