Why at no load armature current is zero?

Explanation: At no load the power taken by the motor is zero (assuming all the losses are neglected) and P = VI. For shunted DC motor the voltage will still provide for the field. To make the power zero, armature current needs to be zero.

What is no load current of DC shunt motor?

The no-load current is the current required just to turn the motor shaft with nothing connected.

What all may happen if the DC shunt motor running on no load has its shunt field 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.

What happens when DC motor is started without load?

Thus from equation (2), it is clear that speed of DC Series Motor is inversely proportional to Armature Current Ia. 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 are the applications of DC shunt motor?

The applications of shunt DC motor include the following.

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.

What will happen if the shunt motor field winding is left open by mistake?

For a constant back emf, flux is inversely proportional to the speed of the motor. If field winding is disconnected accidentally, the speed would dangerously increase in order to maintain the back emf of the motor.

What would happen if the field of DC shunt motor is open?

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…

What are the advantages of DC series motor?

Advantages of DC Series Motor Dc series motor have good accelerating torque. Dc series motor have a relatively huge starting torques. Dc series motor delivers high torque during an overload. The dc series motor draws less current and power from the source compared to a shunt or compound motor.

Why is the no load armature current not zero in a DC motor?

Still which means the field winding draws its rated current even if the motor is at no-load. DC SERIES MOTOR have field and armature windings connected in series and both carry same current so, For no-load, which means As field current is zero so field flux becomes zero. As speed of a motor is inversly proportional to field flux, so speed tend…

What happens when a DC shunt motor is opened?

As mentioned above if the field circuit is opened, the back emf will drop to zero. With full armature voltage applied this will cause a very large armature current to flow which should normally blow the fuses. While the field current decays the motor will speed up as if in a field weakening mode.

Can a shunt motor run without a field resistor?

There is a thumb rule in DC motors (in your case Shunt), that never ever run the motor without field resistor. WHY: we know that E=K*phi*w in DC machines, so when the field is open or if=0, the generated flux (phi) is going to be zero, and for the given E, the speed is derived from E/0, so, the developed speed would be infinity.

How is the armature current of a DC motor calculated?

If it’s a motor, the armature current is electrical power provided by the power supply to the armature windings in order to create a magnetic field to oppose the magnetic field of the field winding and thereby create rotational energy (torque) that can be used to do work. Which current is greater, armature or field current in DC?

Why at no load armature current is zero?