TORQUE CONTROL CIRCUIT FOR CAPACITOR STARTING TYPE SINGLE- PHASE INDUCTION MOTOR

摘要

PURPOSE:To prevent a decrease in the number of revolutions with a simple structure by a method wherein an all firing type current is supplied to a starting coil when the number of revolutions has decreased to a predetermined value or below. CONSTITUTION:The primary side of a current transformer 1 detecting a current value supplied to a main coil L1 is connected to the main coil L1. A starting capacitor Cs and a triode AC switch 2 are connected to a starting coil L2 in series. A high load acts on a rotor and when the number of revolutions decreases, the current value of the main coil L1 increases. This increase is detected by the current transformer 1 and a thyristor 3 is conducted with suitable timing to shift phase through the starting capacitor Cs and the starting coil L2 is excited to provide rotating torque and to drive the rotor at constant speed rotation.