# What would happen if the field of DC shunt motor is open?

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## What happen if the field winding of a running shunt motor suddenly breaks open?

As we know, if the field winding of a running shunt motor suddenly breaks open. So, Flux is reduced and speed increase dangerously as flux is inversely proportional to speed.

## What will happen to the DC compound motor if the shunt field is opened when the motor is operating at light load?

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.

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## What will happen if the DC shunt motor running on no load has its shunt field winding opened accidentally?

Ans: if a shunt motor, running at no load has its shunt field opened or burnt out, the back emf will fall to nearly zero . the armature current will continuously increase the speed of the motor until its parts fly apart.

## What will happen if the field of the DC motor is opened accidentally in no load and full load?

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 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 is the effect of inserting resistance in the field circuit of a DC shunt motor on its speed and torque?

In this method, speed variation is accomplished by means of a variable resistance inserted in series with the shunt field. An increase in controlling resistances reduces the field current with a reduction in flux and an increase in speed.

## What will happen if the field circuit is opened during experiment of speed control of DC shunt motor?

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 will happen if DC motor is used without starter?

What will happen if DC motor is used without starter? Explanation: It would cause intolerably heavy sparking at the brushes which may destroy the commutator and brush-gear. … Explanation: In shunt and compound motors starting the shunt field should be switched on with full starting resistance in armature circuit.

## Why the field control resistance is zero at the time of starting of DC shunt motor?

Answer: At the time of starting of motor, the armature resistance is kept at maximum position to control and reduce the high starting current and field rheostat atminimum position to ensure that speed does not go beyond rated value and to have high starting torque.

## Why DC shunt motor is started on no load?

Since speed is constant and torque (τ) is proportional to armature current (Ia). So that, starting a shunt motor at a heavy load requires a high starting current. In order to avoid this high starting current, shunt motors are not started at heavy loads and they should be started without any load.