Universal motor speed stabiliser - uses triac with series RC network in parallel and has follow-up control diode connected to gate

摘要

The motor (12) is driven from an a.c. source (U) via a thyristor. The stabilising circuit uses the e.m.f. developed by the motor armature, and it is designed in such a way that it functions fully symmetrically without high circuit costs being involved. A bi-directional thyristor or Triac is used and is driven or controlled in the first and third quadrants. A series RC network is connected in parallel with the Triac. A diode in parallel with the capacitor of the RC network is connected to the Triac gate for follow-up control of the Triac in the third quadrant.