PURPOSE: To make a snubber circuit compact, by a method wherein one of the snubber circuit is constituted so as to absorb overvoltage of the whole, and other is constituted so as to absorb overvoltage applied to the element.
CONSTITUTION: Three-phase power source U, V, W is controlled by arm constitution elements U+, U-, V+, V-, W+, W-, and supplied through a series reactor Ld to a load LL. A capacitor Cf is constituted by a smoothing capacitor, and the constituent element U+ is composed of a first snubber circuit comprising a transistor UTr+, a diode UD+, a snubber capacitor Ct and a snubber resistor Rt, and of a second snubber circuit comprising a snubber capacitor Cd and a snubber resistor Rd. Overvoltage at cutoff state of the transistor UTr+ is absorbed by the first snubber circuit. Reverse voltage generated at power source commutation and applied to the diode UD is absorbed by the second snubber circuit. Since the second snubber circuit may absorb the overvoltage by inductance component of wiring around the diode, it can be made compact.
SHIMA KIYOYA
ANDO TAKEYOSHI
INABA HIROMI
MEGURO TOSHIO
| JPS5910165A | 1984-01-19 |