DYNAMIC BRAKE CIRCUIT AND SEMICONDUCTOR INVERTER USING DYNAMIC BRAKE CIRCUIT

摘要

The invention prevents a voltage change dv/dt of an inverter from directly causing an erroneous firing of a semiconductor brake switch, which may short-circuit the inverter during operation. To brake a motor (10) driven by an inverter which consists of a three-phase AC power supply (1), a three-phase bridge rectifier (3), a smoothing capacitor (6) and a semiconductor switching element (7), a dynamic braking circuit turns on a semiconductor braking switch (14) to short-circuit feeder lines (11) for the motor (10) so that a braking resistor (15) may absorb energy. A large resistor (20) is connected between the positive side of the smoothing capacitor (6) and the positive side of the semiconductor braking switch (14), and a snubber capacitor (17) of a snubber circuit (18) connected in parallel with the semiconductor braking switch (14) is charged through the resistor (20) before the inverter is started. IMAGE