# Which DC motor has got maximum self relieving property?

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## Which of the following DC motor has maximum self relieving property?

Which DC motor has got maximum self-relieving property? Explanation: DC series motor develops large starting torque initially and slow down with increase in load and so get automatically relived from heavy excessive load. Thus, DC series motor is called as self-reliving machine.

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.

## In which case we will get maximum power from DC motor?

The maximum power is developed in the motor when the back emf is equal to half of the supply voltage.

## Which part of the DC motor can sustain maximum temperature rise?

Field winding in a DC motor is not a rotating part. It is present away from the rotating part of the machine. So, temperature rise in the machine will not produce any effect on the machine rotation. Thus, field winding can sustain the maximum temperature rise.

## Which DC motor is more preferred for elevators?

DC cumulative compound motor having high starting torque up to 450% depending upon the degree of compounding. The speed regulation is varying up to 25 ~ 30%. That’s why these motors are used in elevators.

## What are series DC motors used for?

Series DC motors are generally used where high starting torque is required, and speed variations are possible. These types of direct connection motors are, for instance, used in the traction system, cranes, air compressors, vacuum cleaners, sewing machines, etc.

## Which DC motor is preferred for constant speed?

Which D.C motor is preferred for machine tools? Explanation: DC shunt motor is a constant speed motor tool machine such as lathe machine requires being run at a constant speed. As lathe machines roll down iron pieces reducing Diameters at a constant speed.

## Why starting current is high?

At start, the reactance of the rotor is high because the slip of the motor is equal to unity. The value of Rr/s increase as the slip gets decrease. When the induction motor is started the rotor reactance is more than the rotor resistance and because of the large Xr/Rr ratio the motor takes large inductive current.

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## Why is the DC motor preferred over AC motor?

D.C. motor is preferred over an A.C. motor when we need variable speed operation because As in DC series motor field winding and armature winding is in series. So whenever armature current changes field current also changes as they are same due to which its torque changes rapidly and we get a variable speed.

## Which case will get maximum power?

The condition for maximum power in case of D.C. motor is

Supply voltage =1/2 × back e.m.f.

## Where is flux maximum DC motor?

The flux is maximum under leading pole tip of a dc motor.

## What is the efficiency of the DC motor at maximum power?

Explanation: For getting maximum power, derivative of power with respect to current is equal to 0. This is practically impossible to achieve as, current required is much more than its normal rated value. Large heat will be produced in a machine and efficiency of motor will be less than 50 %.

## Which of the following motors has the highest no load speed?

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 part will surely that given motor is DC motor and not an AC type?

Commutator will surely tell that given motor is DC motor and not an AC type. 3.

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