Advantages and Disadvantages of Induction Motor
June 8, 2024 by Electrical4U
 
Contents
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Key learnings:- Induction Motor Definition: An induction motor is defined as an electric motor that operates on alternating current (AC) and uses electromagnetic induction to generate motion.
- Simple Construction: Induction motors have a simple and robust construction, making them reliable and low maintenance.
- Advantages of Induction Motors: They include low cost, high efficiency, high starting torque, and safe operation without sparks.
- Disadvantages of Induction Motors: They include lack of self-starting torque in single-phase motors, poor power factor at light loads, and difficulty in speed control.
- Efficiency Range: Induction motors are highly efficient, with efficiency rates ranging from 85% to 97%.
Advantages of Induction Motor- The most important advantage of an induction motor is its simple construction. The stator’s design is similar in both Synchronous motors and induction motors. However, unlike synchronous motors that need slip rings for the rotor, Squirrel cage induction motors do not. This makes induction motors easier to maintain compared to DC Motors, as they do not have brushes.
- The operation of an induction motor is independent of environmental conditions because it is robust and mechanically strong.
- A Squirrel cage induction motor does not contain Brushes, Slip rings and Commutators. Due to this reason, the cost of the motor is quite low. However, Slip Rings are used in Wound type induction motor to add external resistance to the rotor winding.
- Without brushes, induction motors do not produce sparks, making them safe for use in hazardous conditions.
- Unlike synchronous motors, a 3 phase induction motor has a high starting torque, good speed regulation and reasonable overload capacity.
- Induction motors are highly efficient, with full load efficiency ranging from 85% to 97%.
Disadvantages of Induction Motor- A single phase induction motor, unlike a 3 phase induction motor, does not have a self starting torque. Auxiliaries are required to start a single phase motor.
- During light load conditions, the power factor of the motor drops to a very low value. This is because during the start, the motor draws a large magnetising current to overcome the reluctance offered by the air gap between the Stator and the Rotor. Also, the induction motor will take very less current from the supply main. The vector sum of Load current and Magnetising current lags the voltage by around 75-80 degrees and hence, the power factor is low. Due to high magnetising current, the copper losses of the motor increase. This in turn leads to decrease in the efficiency of the motor.
- Speed control of an induction motor is very difficult to attain. This is because a 3 phase induction motor is a constant speed motor and for the entire loading range, the change in speed of the motor is very low.
- Induction motors have high input surge currents, which are referred to as Magnetising Inrush currents. This causes a reduction in voltage at the time of starting the motor.
- Due to poor starting torque, the motor cannot be used for applications which require high starting torque.
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