Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?

Increased I R losses
Increased core losses
motors which are fed from thyristor bridge circuits ? A. Increased I R losses B. Increased core losses C. Poor commutation
Change in motor parameters E. All of the above

The correct answer is: E. All of the above

Thyristor bridge circuits are used to control the speed of DC motors. However, they can also cause a number of problems, including:

  • Increased IR losses: Thyristors are not perfect switches, and they always have a small amount of resistance. This resistance causes the motor to lose power, which can lead to increased heating and decreased efficiency.
  • Increased core losses: Thyristors also cause the motor’s magnetic field to fluctuate, which can cause increased core losses. Core losses are the energy that is lost in the motor’s magnetic core due to eddy currents and hysteresis.
  • Poor commutation: Thyristors can also cause poor commutation, which is the process of switching the current from one winding to the next in a DC motor. Poor commutation can cause sparking and vibration, which can damage the motor.
  • Change in motor parameters: Thyristors can also cause changes in the motor’s parameters, such as its inductance and resistance. This can make it difficult to control the motor’s speed and torque.

To minimize these problems, it is important to use a thyristor bridge circuit that is designed for use with DC motors. The circuit should also be properly tuned to the motor’s characteristics.