This circuit can in reality tune down an asyncronous motor (as e.g. found in old tape recorders) to low rpm in a stable way, opposed to the usual steep torque decline causing the motor to stop (the DC current caused by the diode enables this). Use about 3/4 of the motor's nominal voltage for supply.
A thyristor used in the real circuit here is represented by two transistors and a 100 Ohm resistor, and the async motor by two motor items. The simulation does not work properly and the parts dimensionings are soewhat makeshift (makes likely no sense in this case anyway).
Use caution when trying this out. Use at your own risk!
