What is Single Phase Motor?
Single phase induction motors are a type of asynchronous AC motor that runs on single phase power and are commonly used in small appliances and other equipment that don't require a lot of power. They are not self-starting, so they require a starting mechanism such as a capacitor to get them up and running.
The capacitor start technique is the most common starting method for single phase induction motors. It involves using a capacitor in the auxiliary winding to generate a 90° phase shift, which creates the rotating magnetic field (RMF) needed to start the motor. Other starting methods for single phase induction motors include split phase, capacitor start capacitor run, and shaded pole.
What is Three phase Induction Motor?
Three phase induction motors are a type of asynchronous AC motor that run on three phase power and are commonly used in industrial and commercial applications. They are able to generate a smoothly rotating magnetic field (RMF) in the stator windings due to the three alternating currents flowing in the windings that are 120° apart.
Three phase induction motors can be connected in either a star or delta configuration, depending on the specific requirements of the application. They are generally more efficient and have a longer lifespan than single phase induction motors, as they don't rely on an external device like a capacitor to generate the RMF.
Difference Between Single-Phase and Three Phase Induction Motor
| Single Phase Induction Motor | Three Phase Induction Motor | |
|---|---|---|
| Power supply | Single phase AC | Three phase AC |
| Number of terminals | 2 | 3 or 4 (including neutral) |
| Self-starting | No | Yes |
| Starting mechanism | Required | Not required |
| Direction control | Swapping polarity of starter winding | Swapping any two input phases |
| Types | Spilt phase, shaded pole, capacitor start, capacitor start capacitor run | Squirrel cage, wound type |
| Slip | Forward and backward | Only forward |
| Noise and vibration | High | Low |
| Copper losses | High | Low |
| Efficiency | Lower | Higher |
| Power rating | Below 5 kW | Above 5 kW |
| Starting torque | Limited | High |
| Size | Larger | Smaller |
| Design complexity | Simple | Complex |
| Maintenance | Easy | Difficult |
| Cost | Cheaper | More expensive |
| Reliability | High | Lower |
| Applications | Household and offices, small loads in industries (fans, water pumps, drills, etc.) | Heavy mechanical loads in industries |
- Supply: Single-phase induction motors use a single-phase power supply, while three-phase induction motors use a three-phase power supply.
- Starting torque: The starting torque of single-phase induction motors is lower than that of three-phase induction motors.
- Maintenance: Single-phase motors are easier to repair and maintain compared to three-phase motors.
- Construction: Single-phase motors are simpler in construction compared to three-phase motors.
- Efficiency: Single-phase motors have lower efficiency compared to three-phase motors.
- Power factor: The power factor of a single-phase motor is lower than that of a three-phase motor.
- Applications: Single-phase motors are mainly used in household appliances, while three-phase motors are commonly used in industrial settings.