Speed control circuit for DC motor supplied from AC mains - has comparator controlling thyristor via limiters and triggers for operation from two static converters

摘要

The speed control circuit, for a dc motor supplied from two or more static converter bridges coupled to an ac supply, has a comparator comparing a reference value with the actual value of a parameter (e. r. current) of the motor. The output of the comparator is passed over 3 amplifiers and 3 limiters to 3 pairs of triggers. - Each pair of triggers controls the two thyristors in each of the 3 converter bridges coupled to the 3 secondaries of the mains transformer. Constant current sources are connected to the inputs of the triggers. The limiters and constant current sources have different limits and current respectively. This avoids the use of staged Zener diodes.