Frequent question: 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.

Why DC shunt motor is not starting with heavy loads?

This is because of stray losses. The heavy starting loads require more armature current, so shunt motor should not be started on heavy loads. … Consider when starting a series motor the current flowing will be high, but the flux that the motor produces will be moderate since the series winding has less number of turns.

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

Answer : Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease. Answer : With the increase in load on a d.c. shunt motor, speed of the motor reduces slightly.

Why dc series motor is not started at no load?

A series motor should never be started at no load. With no mechanical load on the series motor, the current is low, the counter-EMF produced by the field winding is weak, and so the armature must turn faster to produce sufficient counter-EMF to balance the supply voltage. The motor can be damaged by overspeed.

Why do DC series motors start loading?

At the starting of the motor there is no back emf, so large current current flows cause high starting torque. This starting torque leads to very fast acceleration of motor if shaft is not connected to any load. This fast acceleration cause motor to damage. So series motor are always started with load.

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 applications of DC shunt motor?

DC Shunt Motor Applications

  • These motors are used wherever stable speed is required.
  • This kind of DC motor can be used in Centrifugal Pumps, Lifts, Weaving Machine, Lathe Machines, Blowers, Fans, Conveyors, Spinning machines, etc.
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Why DC shunt motor is constant speed?

If the load on the motor increases armature speed reduces and thereby cause a reduction in the back emf. … Hence, a DC shunt motor always maintains a constant speed. Under no load condition, the back emf becomes nearly equal to the applied voltage.

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.

What are the characteristics of DC shunt motor?

Characteristics of a DC Shunt Motor:

  • Speed-Armature Current Characteristic: …
  • Torque-Armature Current Characteristic: …
  • Speed-Torque Characteristic: …
  • Break in Field Circuit of a DC Motor:

Can we start the DC shunt motor and series motor without load?

We can operate a shunt motor with no load because their torque is not that high as series motors. They are moreover constant speed motors and tend to operate at stable speeds. Series motors cannot be started without load, as they tend to overspeed and get damaged. Motor armature current is decided by the load.

What is no load current in dc motor?

The no-load current is the current required just to turn the motor shaft with nothing connected. It is the current required to overcome the bearing and brush friction plus the aerodynamic drag caused by the rotor moving in the air and moving air through the motor for cooling purposes.

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Is advised not to run dc series motor with no load why?

It is advised not to run dc series motor with no load. … Explanation: If the torque is zero in dc series motor then the speed will be infinite causing the damage of the machine permanently.

Which motor is always started with load?

At no load, it will rotate at dangerously high speed 2. It will fail to start 3. It will not develop high starting torque 4.

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.

Why should a series motor always be connected to a load?

Answers and Replies

Consider when starting a series motor the current flowing will be high, but the flux that the motor produces will be moderate since the series winding has less number of turns. If u start the motor without load the speed will increase. as speed increases the back emf increases.