Single phase induction motor needs a single-phase AC supply, while a 3-phase induction motor needs a three-phase AC supply for its operation. The three-phase induction motor produces more torque compared to a single-phase induction motor.
An induction motor is an electrical machine that generates mechanical power and torque using the principle of electromagnetic induction. The rotor of the induction motor rotates due to the magnetic field induced by the stator of the induction motor. Based on the type of AC power supplied to the induction motor, it is divided into the following two types:
- Single-phase induction motor
- Three-phase induction motor
In this article, we will discuss the key differences between single-phase induction motor and three-phase induction motor. on the basis of their construction, working, applications, and other characteristics. But before that let’s look into the basics of each of the two induction motors in the first two sections.
What is a Single Phase Induction Motor?
Single Phase Induction Motor is a kind of AC induction motor that utilizes a one-phase power supply to function and generate electric current, mechanical power, and required torque depending on the type of applications it’s used. The single-phase induction motor finds its applications in a wide range of domestic and industrial appliances and machines, due to its cost-effectiveness, easy accessibility, performance rate, and closeness to the unity power factor.
Single-phase AC induction motors can be further subdivided into the following three types:
- Single-phase asynchronous induction motors.
- Single-phase synchronous induction motors.
- Commutator induction motors.
A single-phase induction motor is comprised of two main components namely – the stator and rotor. The stator remains in a fixed position and is supplied with a single-phase AC power supply. While the rotor of the single-phase induction motor rotates due to the rotatory magnetic field produced at the double wounded stator. The rotor is mostly of the squirrel cage rotor type.
What is a Three Phase Induction Motor?
Three Phase Induction Motor is a kind of AC induction motor that utilizes a three-phase power supply to function and generate electric current, mechanical power, and required torque depending on the type of applications it’s used.
Three phase induction motor is also referred to as a self-starting induction motor due to the fact that there is a phase difference of 120 degrees electrical between the stator windings in each of the three phases along with a 120-degree electrical phase difference present within the three-phase power supply. This results in the three-phase induction motor to start rotating on its own due to the generation of the rotatory magnetic field in one direction present in the air gap between the stator winding and the rotor.
The three-phase induction motor works on the principle of Lenz’s law, which is similar to the operation of a single-phase AC motor but differs due to the three-phase power supplied to the stator winding.
The three-phase AC induction motors can be classified into the following three categories:
- Squirrel cage three-phase induction motor
- Wound rotor three-phase induction motor
- Double cage rotor three-phase induction motor.
Difference Between Single-Phase and Three Phase Induction Motor
Based on different characteristics and properties, the following table illustrates the most prominent differences between Single Phase and Three Phase Induction Motor.
| Parameter | Single Phase Induction Motor | Three-Phase Induction Motor |
| Definition | Single-phase motor utilizes one phase supply current to operate | Three phases motor utilizes three phase supply current to operate |
| Types of motors | Single-phase induction motors can be of three main types namely – Single-phase asynchronous induction motors, Single phase synchronous induction motors, and Commutator induction motors. | Three-phase induction motors can be broadly classified into 3 main types, viz. Squirrel cage three-phase induction motor, Wound rotor three-phase induction motor, Double cage rotor three-phase induction motor. |
| Working principle | Single-phase induction motor works on the principle of electromagnetic induction. | Three phases induction motor operates on the principle of electromagnetic induction. |
| Motor characteristics | The single-phase induction motors have a relatively simple structure, rate of performance, and reasonable cost in comparison to three-phase induction motors. | The three-phase induction motors have complex system designs and are relatively expensive. |
| Self-starting Property | Single-phase induction motors are not self-starting. Hence, they have to be provided with some external means to start them. | Three-phase induction motors have a rotating magnetic field which makes them self-starting. |
| Upkeep | Due to the simple motor design, the maintenance and installation of a single-phase induction motor are much simpler. | Due to the complex motor design, the maintenance and installation of a three-phase induction motor is hard. |
| Performance | The efficacy of a single-phase induction motor is relatively low. | The efficacy of three-phase induction motors is relatively high. |
| Torque | The torque at the beginning of the single-phase motor rotation is relatively low. | The torque at the beginning of the three-phase motor rotation is relatively high. |
| Power factor | The single-phase induction motor has a relatively poor power factor value farther away from unity. | The three-phase induction motor has a better power factor nearer to unity. |
| Applications | Single-phase motors find their applications in numerous home appliances such as fans, mixers, etc. | Three-phase induction motors find their applications for commercial purposes in large factories and power stations to run heavy mechanical loads. |
Conclusion
In conclusion, this article highlights the main differences between single-phase and three-phase induction motors. While the single-phase induction motors have a simpler motor design and are available at a highly affordable rate, the three-phase induction motors are comparatively complex in design and very expensive. But the three-phase induction motors are used for large-scale industrial applications to drive heavy machinery, while the single-phase induction motors are used to run small devices such as fans, geysers, compressors, etc.
