Single-phase AC motor is as popular as two phase AC motor and three phase AC motor because they are useful in many fields. It is the main source of power in the applications of industrial and household of small horsepower. When the three-phase power supply is not available or impractical, it is the time of single phase motor. Although single-phase motor don’t get the higher efficiency like three-phase, but it has a longer service life with less maintenance.
Occasionally manufacturing defect could lead to motor fault at early stage. However, most of the failure is raised from the improper application. Before replacing the failed one or choosing a new designed application system for AC motor, special attention should be paid to the application requirements. Wrong choices of motor type and power can cause repeated motor fault and equipment downtime. Obviously, you shouldn’t choose the motor with too small power, which can lead to premature motor fault of electrical stress, neither you should choose too powerful one as well because it can also has a serious impact due to its force or inherent design features. For example, motor with high locked-rotor and breakdown torquecan damage its drive device. In addition, the motor working under rated load has a low efficiency and lead to electricity waste.
Knowing the characteristics of the main types of single-phase motor is as important as knowing the size of the motor applications. In general, connecting to the polyphase line of ac polyphase squirrel-cage motor will start torque. Although a squirrel cage motor connected to the single-phase circuit will not start torque, it operates like polyphase AC motors by some external device. In many types of AC motors, single-phase motors are mostly distinguished by the device they started.
The split-phase motors, also known as induction start motor are used in industrial field, and it is the simplest single-phase motor. It has two windings: start and main winding. Starting winding has thinner wire and less rotation than main winding in order to create more resistance to make the motor operate.