376device Protection In A Motor Controller

Switches Sj-S4 form a bridge converter and the devices require protection against overvoltage spikes from circuit inductances. The main factors are: (1) minimize circuit inductances by careful layout. The key element is the position of D9 and associated decoupling capacitor relative to Dj-D4; (2) fit 1 mF of ceramic capacitors across the DC bridge S1 /S4 plus varistor overvoltage protection.

DrD4 can be normal rectification grade components but D9 must be a fast diode with soft recovery. D5-D8 are built into the transistor blocks.

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