# Frequent question: Why is it dangerous to lose the field of a shunt motor

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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 the field of the DC shunt motor is accidentally removed?

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…

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## What will happen if a shunt motor running at no load has its shunt field 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 parts of motor may even fly apart.

## What does a shunt field do?

These are generators that produce direct current (DC) and alternators that produce alternating current (AC). Main or shunt field windings are used to control the no-load output of a generator.

## What are the limitations of shunt field control?

Disadvantages of Field Rheostat Controlled DC Shunt Motor

Creeping speeds cannot be obtained. Top speeds only obtained at reduced torque. The speed is maximum at minimum value of flux, which is governed by the demagnetizing effect of armature reaction on the field.

## What will happen when DC shunt motor is started with load?

If the DC shunt motor is started with heavy load, the armature current may rise to very high value causing damage to armature winding. … Motor armature current is decided by the load. On less load or no load, the armature current drawn by the motor is very small.

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

If the load on the motor increases armature speed reduces and thereby cause a reduction in the back emf. Hence, when back emf decreases the armature current increases. So the torque increases with the increase in current and accelerates the armature which maintains its speed with the additional load.

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## Why the efficiency of DC shunt connected motor is low when it is running at low load?

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.

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. It is advisable that motor should not be used beyond some load value, as it may damage itself by self-loading. 5.

## Which motor should not be started on no load?

Speed of DC Series Motor ωm = Very high, which is also clear from the Speed Current Characteristics of DC Series Motor as shown in figure above. Therefore if the DC Series Motor is started at No Load then the speed of DC Series Motor will become dangerously high which will definitely damage the DC Series Motor.

## What is the main advantage of a shunt motor?

Shunt Motors

The shunt-connected motor offers good speed regulation. The field winding can be separately excited or connected to the same source as the armature. An advantage to a separately excited shunt field is the ability of a variable speed drive to provide independent control of the armature and field.

## Why DC shunt motor is constant speed?

Since torque is proportional to armature current, torque also increases. Finally, this increased torque allows the motor to increase its speed and compensate for the slowdown due to loading. Hence, a DC shunt motor is able to self-regulate its speed, and can be referred to as a constant speed motor.

## What is the difference between a shorted motor and a shunt motor?

What is the difference between a shorted motor and a shunted motor? A shunt motor has the field windings connected in parallel with the armature and a series motor has the field windings connected in series with the armature15.

## How do you control the speed of a DC shunt motor?

Speed control of Shunt motor

1. Flux control method. It is already explained above that the speed of a dc motor is inversely proportional to the flux per pole. …
2. Armature control method. …
3. Voltage Control Method. …
4. Flux control method. …
5. Variable resistance in series with armature. …
6. Series-parallel control.

## What is field weakening mode control?

The project, with the title Torque Control in Field Weakening Mode, is a proposal from Danfoss. The main idea of the project is to control the speed and torque of an Interior Permanent Magnet Synchronous Machine(IPMSM) in the flux weakening regime, considering the voltage and current limits of the inverter .

## How do you control the speed of an AC motor?

The Variable Frequency Drive is a particular kind of adjustable-speed drive that is used to control the speed of an AC motor. In order to control the motor’s rotational speed, a Variable Frequency Drive controls the frequency of the electrical power supplied to it.