Why the rheostat of the field winding of a DC shunt motor kept low at starting?

In case of DC motor the speed of the motor is inversly proportional to flux and the flux is directly proportional to current so during starting of motor the speed is limited by keeping the rheostat in minimum. So field current is maximum, flux is maximum and speed is minimum.

What is position of rheostat connected in field of AC generator?

The field rheostat is connected in series with the shunt field circuit. This provides the simplest method of controlling the terminal voltage of a dc generator.

Why is it necessary to cut out all the resistance in the field rheostat while stopping the motor?

Precaution While stopping the motor, all the resistance in the field rheostat is cutout, so that motor speed falls to its normal value; then the line switch is opened. This procedure ensures that, the next time the motor is started, it will be with a strong field and resultant strong starting torque.

How does the speed vary when the armature rheostat is adjusted?

As we increase the resistance R of the rheostat, the field current Ish decreases. So the flux φ decreases. This results in increasing the speed of the motor. As the R is increased, the speed increases.

What is position of rheostat connected in field of shunt motor?

Answer: At the time of staring shunt motor field rheostat is minimum and armature rheostat is maximum.

What is a field rheostat?

Definition of field rheostat : a rheostat for regulating the current supplied to the field winding of a generator or motor.

What are minimum and maximum positions of rheostat?

Why rheostat is used in generator experiment?

rheostat, adjustable resistor used in applications that require the adjustment of current or the varying of resistance in an electric circuit. The rheostat can adjust generator characteristics, dim lights, and start or control the speed of motors.

What is cut in and cut out position of rheostat?

Rheostat is a variable resistor. It has three terminals. 2 fixed terminals and one variable terminal to vary the resistance. It can be kept in either cut in or cut out position. If kept in cut out position it offers zero resistance.

Why is armature control is superior to field control in the speed control of DC shunt motor?

Limits on speed: If your application requires you to adjust the motor below the normal speed, you may be better off choosing an armature controlled method. Field controlled DC motors can only operate above the normal speed. Higher speeds can also result in less torque.

Which rule determines the direction of rotation of armature in DC motor?

Answer: The direction of rotation of a DC motor depends on the direction of the magnetic field and the direction of current flow in the armature. If either the direction of the field or the direction of current flow through the armature is reversed, the rotation of the motor will reverse.

How can the direction of rotation of a DC shunt motor be reversed?

The direction of rotation of DC shunt motor can be reversed by reversing either field terminals or armature terminals but not both. The torque can be changed by changing either field flux or armature current. Hence the motor will rotate in the same direction by changing the supply connections.