Single phase induction motor with two windings - with auxiliary winding divided into two branches in series with capacitor and resistor

摘要

The modified auxiliary winding circuit is intended to assist starting. The auxiliary winding is divided into two parallel branches (3, 4). One branch is in series with a capacitor (6), the other with a positive temp. coefficient resistor (5). At starting, the PTC resistor (5) has a low value and the current flows through both auxiliary coils to give a high starting torque. As the PTC resistor heats up, its resistance rises to a high value and effectively switches off the winding (3) in series with it. The motor then runs on the main (2) and capacitor-linked auxiliary winding.