Why do induction motors produce heat?

Electrical
1

Induction motors produce heat due to several reasons which includes:

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  1. Electrical Overload

  2. Induced Rotor Currents

  3. Slip between Stator and Rotor

  4. Stator Winding Resistance

  5. Friction and Windage Losses

  6. Stator Core Losses

  7. Overload and Stall Conditions

Electrical Overload

The overvoltage supply or over work which is caused by taking more current results in heating problems. As the motor operates harder or under a state of abnormally high load, heat production will be the primary outcome and thus, failure.

Induced Rotor Currents

In the induction motor, the stator’s revolving magnetic field cuts the rotor windings through which it creates the flow of currents. These induced rotor currents while producing a torque also produce heat as a result of the resistance offered by the rotor conductors.

Slip between Stator and Rotor

It is clear that slip can be described as the difference between synchronous speed and asynchronous speed, whereby synchronous speed refers to the velocity at which the rotating magnetic field of the stator rotates, while the asynchronous speed refers to the velocity at which the rotor rotates.

Induction motors are always tapered off slightly below the synchronous speed of the rotating stator magnetic field. This “slip” is needed for inducing rotation in the rotor, however, it results in power lose and heat formation.

Stator Winding Resistance

The stator windings have resistance which results to heating losses in the form of I2R whenever current passes through them. Any increase in the stator currents results in an increase in losses hence more heat.

Friction and Windage Losses

During the rotation of the rotor there is always mechanical loss within the bearings mainly caused by friction and windage loss caused by rotation of the rotor through air. These losses are in form of heat.

Stator Core Losses

Additional losses that take place in the stator core include eddy currents and hysteresis losses and also the generation of heat. These losses rise with the operating frequencies and they are highest in the lower frequencies and decrease with increase in frequencies.

Overload and Stall Conditions

When an induction motor is stalled or overloaded the rotor cannot accelerate. This leads to the increase of the slip, causing very high currents in the rotor. This creates high amperage demanding high wattage leading to a rapid rate of thermal increase which can harm motor windings.

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