What will happen if the shunt field is open during running?

As mentioned above if the field circuit is opened, the back emf will drop to zero. The motor will try to speed up to develop a back-emf and with no field it requires a very large armature current. That is why one never starts a shunt motor without the field winding excited.

What will happen if shunt field suddenly opens in a differential compound DC motor?

Explanation: If shunt field is suddenly opened, flux due to shunt field will become 0. As, net flux is equal to shunt field flux – series field flux, the direction of flux will be reversed and thus motor will run in opposite directions.

What will happen if the shunt field winding opened accidentally during the experiment?

Ans: if the shunt field winding of a loaded shunt motor accidentally breaks, the loss of shunt field current would result in stopping of the motor or burn out the armature or fuse.

What will happen when a field of a DC shunt motor gets opened while the motor is running?

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 a shunt motor running at no load has it shunt winding opened accidentally?

What will happen if the d.c. shunt motor opened accidentally running on no-load has its shunt field winding? The field will be reduced to only to the value of residual flux. The speed will be very high. The parts of motor may even fly apart.

What happens to a shunt motor when the armature current decreases during operation?

So now as low current will flow through the field winding as well as armature winding ( as it is series motor) so main flux produced will be lesser, as before saturation point current is directly proportional to flux. So as main flux is lower, speed will tend to increase.

What will happen if the back emf of a DC motor vanishes suddenly?

Detailed Solution. If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.

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 all may happen if the DC shunt motor running on no load has its shunt field winding opened accidentally?

When the motor runs on no-load condition what happens to the back emf?

On the other hand, if there is no mechanical load on the motor, it increases its angular velocity until the back emf is nearly equal to the driving emf. Then the motor uses only enough energy to overcome friction. I=V/R=(8.0V)/(0.400Ω)=20A.

What will happen if suddenly load is removed from the motor?

What occurs if the load is removed from an operating series DC motor? It will stop running.

Why does the current through a motor decrease when the motor speeds up?

As the motor picks up speed, relative speed between field and rotor decreases. Therefore rotor emf decreases and hence currents in rotor and stator also decrease.