Which of the following will not be the nature of torque produced when a DC series motor is accidentally connected to a single phase supply?

1. Steady & unidirectional

2. Pulsating & unidirectional

3. Oscillating

When AC supply is given to DC series motor:

• An AC supply will exert pulsating & unidirectional torque because the direction of armature current and field current reverses at the same time and the direction of rotation will be as it is.
• Due to the presence of alternating current, eddy currents are induced in the yoke and field cores which causes excessive heating of the yoke and field cores.
• The power factor becomes low because of the high inductance formed by the field and armature circuit.
• There is sparking at the brushes of the DC series motor.