What is a Single Phase Motor?
Single phase motors generally refer to low-power single phase asynchronous motors powered by a single phase AC power supply. It is also called a single phase induction motor. This kind of motor usually has two phase windings on the stator, and the rotor is of ordinary squirrel cage type. The distribution of the two phase windings on the stator and the different power supply conditions can produce different starting characteristics and operating characteristics.
Single phase motors have a large production volume and are closely related to people's daily lives. Especially with the improvement of people's living standards, the consumption of single phase motors for household appliances is also increasing.
How does it work？
When a single phase sinusoidal current passes through the stator windings, the motor generates an alternating magnetic field. The strength and direction of this magnetic field change sinusoidally with time, but its orientation in space is fixed, so this magnetic field is also called an alternating pulsating magnetic field. This alternating pulsating magnetic field can be decomposed into two rotating magnetic fields with the same speed and opposite rotation directions. When the rotor is stationary, the two rotating magnetic fields produce two equal and opposite torques in the rotor, so that the combined torque is zero, so the motor cannot rotate. When we use external force to rotate the motor in a certain direction (such as clockwise rotation), then the movement of the cutting magnetic field lines between the rotor and the clockwise rotating magnetic field becomes smaller; the difference between the rotor and the counterclockwise rotating magnetic field The cutting magnetic field line movement becomes larger. In this way, the balance is broken, the total electromagnetic torque produced by the rotor will no longer be zero, and the rotor will rotate in the direction of pushing.
We can add a start winding to the stator so that the single phase motor can rotate automatically. The start winding and the main winding are spaced apart by 90 degrees. The start winding should be connected in series with a suitable capacitor for approximately 90 degrees phase difference with the current of the main winding, which is the principle of phase separation. Two currents that are 90 degrees apart in time pass through two windings that are 90 degrees apart in space, which will generate a (two-phase) rotating magnetic field in space.
Under the action of this rotating magnetic field, the rotor can start automatically. After starting, when the speed rises to a certain level, the start winding is disconnected using a centrifugal switch or other automatic control device installed on the rotor, and only the main winding works during normal operation. Therefore, the start winding can be made into a short-time working mode. But there are many times, the starting winding is not disconnected. We call this kind of motor a single phase motor. To change the direction of this kind of motor, just change the terminal of the auxiliary winding.
Types of single phase motors
In household appliances, induction motors are often equipped, especially small single-phase AC induction motors. Due to the difference in application categories, Single phase induction motors can generally be divided into split-phase motor, capacitor-start motor, capacitor-start capacitor-run motor, permanent-split capacitor (PSC) motor, shaded-pole motor.
ATO single phase motors have two capacitors (start capacitor and run capacitor) to provide starting torque at rest. They can be used in production: such as micro water pumps, refiners, threshers, grinders, woodworking machinery, medical equipment, etc. In life, they are suitable for electric fans, hair dryers, exhaust fans, washing machines, refrigerators.
