Starting winding electronic switching for single phase motor - using resonant circuit excited by slotted disc driven from shaft and tuned above switch-out speed

摘要

The point at which the starting winding (H1) of the high power single phase motor is switched out is determined by a resonant circuit (24) which is excited by a slotted wheel (6) driven by the motor shaft. The onset of resonance is set at a motor speed slightly higher than the speed at which switch off of the starting winding may take place. The output from the resonant circuit (24) can be taken from a resistor (R3), rectified (D2), and applied to the base of a transistor (T1), forming part of an amplifier, in such a sense as to turn this transistor of thereby removing trigger signals from the solid state switch (D3) in series with the starting winding. An integrator (16) can be added to the resonant circuit output to compensate for component tolerance variations.