Single-phase Motor and Three-phase Motor

An induction motor is a type of AC motor that operates on the principle of electromagnetic induction between the stator and rotor. Induction motors can be designed to operate on single-phase or three-phase power supplies.

A single-phase power supply cannot produce RMF, which requires an additional starting mechanism. So we can say that the main difference is that a single-phase induction motor is not self-starting while a three-phase induction motor is self-starting.

Single-phase induction motor

Single-phase induction motor is a kind of asynchronous AC motor running on single-phase power. It is a low power motor, usually used in homes and offices where single-phase power is supplied from utility poles.

Since single-phase AC cannot produce RMF, it uses a capacitor to generate RMF by creating a 90° phase shift in the auxiliary winding. This type of motor is called capacitor start induction.

Advantages and disadvantages

Single-phase motors are subject to vibration and generate noise during operation. It also wears out its service life.

Single-phase power is less reliable and more expensive than three-phase power. Its power supply is affected by line faults. The copper loss is greater for the same rated current because the current flows through only one winding.

Single-phase AC power is readily available in homes and offices, and the mechanical loads required to drive it are very small. Therefore, it is economical for single-phase motors to drive small loads. Very simple in design and construction, it uses only two windings, which is cheaper and easier to maintain.

Three-phase induction motor

A three-phase induction motor is an AC asynchronous motor that runs on a three-phase power supply. It can operate in either a star configuration or a triangular configuration, depending on requirements. The three-phase produces a very smooth RMF, allowing the motor to run very smoothly without any vibration or noise.

Advantages and Disadvantages

Compared to single-phase power supplies, three-phase power supplies are very reliable and very economical. The power supply is not affected by a single line failure. The stator windings share the current to reduce more copper losses. Therefore they are more efficient.

These motors are often used to drive very heavy mechanical loads in industry because they offer the best efficiency and performance at higher power ratings. Motor losses are much lower than using a single-phase motor with the same rating. Therefore it is ultimately cheaper than a single-phase motor. The relative complexity of the design structure leads to increased motor manufacturing costs. This is why they are relatively quite expensive. 

We can conclude that single-phase motors are more reliable and are a better choice for driving small loads such as home and office appliances. Whereas three-phase motors provide the best performance for driving heavy loads (e.g. in industry). Please contact ZCLGroup to get more.