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

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 will happen if a shunt motor running at no load has it shunt 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.

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What happens if the field of a DC shunt motor gets opened while motor is running?

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. In dc series motor the motor will go to infinite speed (theoretically) as flux is inversely proportional to the speed…

Why DC shunt motor is started on no load?

For DC shunt motor the field resistance is high and armature resistance is low so the variation of flux is very less when rated voltage is applied to the motor and motor speed does not exceeds rated speed at no load. So we can start the DC shunt motor with no load.

What would happen if the field of DC shunt motor is opened * 1 point?

What will be the effect of opening of field of a DC shunt motor while motor is running? Explanation: In a DC shunt motor if supply for the field winding is cut down, the speed would dangerously increase in order to maintain the back emf of the motor.

Why is it dangerous to lose the field of a shunt motor?

Now cutting off the field winding is dangerous for shunt dc motor. As for shunt motor, speed is inversely proportional to field current, so cutting off the field winding results in dangerously high speed. Thus motor gets damaged.

What will happen if excitation of DC shunt motor is changed?

2. What will happen if excitation of DC shunt motor is changed? … Explanation: Speed of the DC motor obtained from speed equation is inversely proportional to flux produced by the field. So, reducing the field current flux produced by armature will decrease, and speed will increase.

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What happens if field winding of shunt motor is short circuited?

If series field winding gets short circuited then effect of series field flux will be lost. Now if terminal voltage decreases then it implies that before short circuiting of the series field winding, series field flux was aiding the main field flux.

What will happen if field winding of shunt motor got accidently disconnected?

SOLUTION. In a DC shunt motor if field winding is disconnected accidently, the speed would dangerously increase in order to maintain the back emf of the motor. For a constant back emf, flux is inversely proportional to the speed of motor.

Why starter is used in DC shunt motor?

Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.

What is the principle of DC shunt motor?

Construction and Working Principle

The working principle of a DC Shunt Motor is, whenever a DC motor is turned ON, then DC flows throughout stator as well as the rotor. This current flow will generate two fields namely pole as well as the armature.

What is the main disadvantage of a shunt motor?

As the load changes, a shunt wound motor runs at a predictable speed. If variable speed is desired, constant speed can be a disadvantage. The lifetime of the motor is usually not improved by brushes.

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How speed of DC shunt motor is controlled?

Field Rheostat Controlled DC Shunt Motor

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 are the advantages of DC shunt motor?

Advantages of Dc shunt motor:

  • The power supply of the DC motor is any way cheap.
  • Shunt would motor able to runs at a predetermined speed.
  • The speed of a dc shunt motor is sufficiently constant.
  • Direct current machines can use for heavy industrial applications where the torque and speed wider range.

Which DC motor has maximum self loading property?

Which DC motor has got maximum self-loading property? Explanation: A differentially compound DC motor, flux reduces so sharply at small increase in load at higher values of load.

Why is the speed of DC shunt motor dependent on back EMF 1 point?

In the case of DC motors Speed ∝ Back emf(Eb)/flux(φ). The field winding is connected across the armature. The resistance offered by the field is constant so the current is constant. … Therefore the speed of the DC shunt motor depends on the back EMF.

Motorization