What will happen if a DC shunt machine is started without field excitation?

Answer: n d.c shunt motor if field winding supply is removed the motor back emf will drop to zero, hence the armature will draw more current to make up the emf. this results in blowing up of fuse.

What is excitation in DC shunt motor?

A DC shunt motor (also known as a shunt wound DC motor) is a type of self-excited DC motor where the field windings are shunted to or are connected in parallel to the armature winding of the motor. Since they are connected in parallel, the armature and field windings are exposed to the same supply voltage.

What would happen if field of DC shunt motor is opened?

Detailed Solution. For a constant back emf, flux is inversely proportional to the speed of the motor. If field winding is disconnected accidentally, the speed would dangerously increase in order to maintain the back emf of the motor.

What will happen if the shunt field of a DC motor is opened during running?

If the shunt field suddenly opens while the motor is being operated under full-load conditions, only a small voltage due to the residual magnetism of the pole pieces will be induced into the armature. Current will increase considerably. The magnitude of this current may be sufficient to burn out the motor.

How can we change the direction of rotation of a DC shunt motor explain with reason?

The direction of rotation of DC shunt motor can be reversed by reversing either field terminals or armature terminals but not both. The torque can be changed by changing either field flux or armature current. Hence the motor will rotate in the same direction by changing the supply connections.

What will happen if DC shunt motor is connected across AC supply?

1. What will happen if DC shunt motor is connected across AC supply? Explanation: In case of parallel field connection, it won’t rotate at all and will start humming and will create vibrations, as a torque produced by positive and negative cycle will cancel out each other. DC motor will be heated up and it may burn.

What can happen to a DC shunt motor if the shunt field should open?

The shunt field must never be opened while the motor is running. If the shunt field suddenly opens while the motor is being operated under full-load conditions, only a small voltage due to the residual magnetism of the pole pieces will be induced into the armature. Current will increase considerably.