Which of the following statements about the losses in a DC motor is INCORRECT?

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SSC JE Electrical 10 Oct 2023 Shift 2 Official Paper-I

In series motors, the field ohmic loss forms a part of the armature circuit loss.
The no load rotational loss is made up of iron loss and mechanical loss.
Stray load losses are produced due to the distortion of the air gap flux due to armature reaction.
Brush losses forms a part of mechanical losses.

Answer 1

The correct answer is option 4.

Power flow in DC motor

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In the DC series motor, the field winding is in series with armature winding. Hence, the field ohmic loss forms a part of the armature circuit loss.
The no-load rotational loss is made up of iron loss and mechanical loss. These are constant losses whether the load is connected or not to the DC motor.
Stray load losses are produced due to the distortion of the air gap flux due to the armature reaction.
In dc machines, there is also a brush contact loss due to brush contact resistance. In practical calculation, this loss is generally included in armature copper loss.