Operating and braking circuit for several AC motors coupled via load - has single brake switch connecting braking resistance bridged by free-running diode across DC voltage rail pair supplying all motors

摘要

The circuit for an AC network (1) has a choke coil (1.5, 1.6 - 5.5, 5.6) bridged by a free-running diode (1.12, 1.13 - 5.12, 5.13) acting as a coupling between a DC voltage rail pair (14, 15) and an intermediate DC circuit capacitor (1.3 ... 5.3) of each motor (19). A braking resistance (10) bridged by a further free-running diode (11) is connected across the DC voltage rail pair (14, 15) via a brake switch (12). An auxiliary capacitor (6) is coupled to the AC network via a rectifier (3) at one side and via individual diode pairs (1.14, 1.15 - 5.14, 5.15) to the intermediate DC circuit capacitor at the other side. The voltage across the auxiliary capacitor is compared with a reference voltage to operate the brake switch when the reference voltage is exceed. ADVANTAGE - Provides common dynamic braking of all AC motors without overvoltages in intermediate DC circuits.