1. Field of the Invention
The invention relates to a motor control circuit, and more particularly to a single-phase AC motor control circuit for a dryer.
2. Description of the Related Art
Nowadays, most motors for dryers employ mechanical centrifugal switches with contacts for starting or for switching control. The mechanical centrifugal switch is connected to a starting winding of a motor of a dryer. As the motor of the dryer is started, and rotation speed thereof is 70%-85% of synchronous speed, the mechanical centrifugal switch is switched on under the action of centrifugal force, switches off the starting circuit and operates. During on/off of the mechanical centrifugal switch, arc spark is generated, which affects work life thereof. In addition, the mechanical centrifugal switch must be disposed in the motor of the dryer, which features complex structure, makes it inconvenient to design overall structure of the motor, and increases size of the motor, and material cost of the motor. It is well-known that during a starting phase, the starting winding and the main winding require comparatively large current, if the starting windings, the main windings, and the heated strips of multiple dryers are simultaneously powered up during the starting phase, starting of the motor is to be affected, and a comparatively large workload is formed, which brings about certain impact on a power system, increases starting time, or even makes it impossible for normal starting, and features imperfect control.