Question: Why does the speed of DC shunt motor fall as load is increased

As the load increases, to maintain the voltage at a constant value, current decreases, due to which the strength of magnetic field produced by the Internal Winding of DC motor decreases. This results in a decreased interaction of the two magnetic fields and thus Decrease in Speed of motor is observed.

When the load of the DC shunt motor increases speed of it will?

Explanation: As the load is increased, speed of the DC motor will reduce slightly, the change is so negligible that in many cases it is assumed that speed of the DC motor remains constant. Hence, characteristic is also called as shunt characteristic.

Which loss of DC motor decreases with load increase?

The rotating armature (aka rotor) produces a back EMF, which opposes the armature voltage and reduces the armature current. If the load on the motor is increased, the armature rotation slows and back EMF is reduced, since back EMF is proportional to speed.

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Does the speed of a shunt motor increase or decrease when the armature current increases?

Therefore, the motor speeds up. When the field current is increased, the field flux is increased. … When the armature voltage and current are both increased, the motor speeds up. In a shunt motor, speed is usually controlled by a rheostat connected in series with the field windings, as shown in figure 2-8.

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

You can start a DC shunt motor without a load, but never start a DC shunt motor with heavy load because, The change in field flux is very less due to the load, so we can assume the flux to be constant. … In order to avoid this high starting current, shunt motors are not started at heavy loads.

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 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:

What will happen with the increase in speed of a DC motor?

Explanation: In case of DC motor, the speed is proportional to the back emf (Ea ∝ N). So, with the increase in speed, the back emf also increases. Therefore, armature current is also decreased, in case of series motor, armature current is equal to the line or load current.

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Which motor has highest no load speed?

3. No-load speed of which of the following DC motor will be highest? Explanation: At no load, armature current tends to zero, flux φ tends to zero, where speed is inversely proportional to the flux, speed will tend to infinity. Thus, no load speed of DC series motor is highest.

Which motor has the poorest speed control?

1. Which of the following DC motor has the poorest speed control? Explanation: DC series motor at no load condition gives infinite speed ideally. Practically it will damage all the armature circuit.

What happens if you increase the current in a motor?

An increase in current is a danger to the motor only if that current exceeds the motor’s nameplate current rating. When amps go above the nameplate rating, heat begins to build up in the motor. Without a timely correction, this heat will damage the motor.

Why does motor current increase with load?

In an electric motor, almost all types, the current is proportional to the torque. If the load increases, in other words, the torque increases and the current will increase. The magnetic field in a motor are related to the voltages. The rotor produces a field that turns at the same speed as the supply.

Why speed decreases as load increases?

As the load increases, to maintain the voltage at a constant value, current decreases, due to which the strength of magnetic field produced by the Internal Winding of DC motor decreases. This results in a decreased interaction of the two magnetic fields and thus Decrease in Speed of motor is observed.

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What are the advantages of DC shunt motor?

Advantages of DC Shunt Motors

  • direct current machines can use for heavy industrial applications where torque and speed wider range.
  • Shunt wound motor able to runs at a predetermined speed.
  • The power supply of DC motor is any way cheap.

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

What will happen if excitation of DC shunt motor is changed? Explanation: The motor will accelerate the mechanical load connected during this period but no increase in the mechanical load as Pload = T1W1 = T2W2 where W2 >W1. So, at the higher speed there is less electrical torque for the same mechanical load / power.

What are the factors affecting the speed of a DC shunt motor?

The above equation shows that the speed depends upon the supply voltage V, the armature circuit resistance Ra, and the field flux Ф, which is produced by the field current. In practice, the variation of these three factors is used for speed control.

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