Load Conditions in Motor

LOAD CONDITIONS IN MOTOR

The load requirements are in either of

·         Speed control

·         Torque control

Depending upon the load requirements the motor has to be chosen.

For example in traction system the load (traction network) needs high starting torque (initiali.e.,high current value is needed at t6he start. A series motor provides a high starting torque as .Hence series motor should be chosen for traction system.

1. Classification of loads

1.     Torque dependent on speed

(Ex-hoists, pumping of water or gas against constant pressure)

2.     Torque linearly dependent on speed

(Ex- motor driving a DC generator connected to a fixed resistance load [generator field value is kept constant])

3.     Torque proportional to square of speed

(Ex- fans, sentrifugal pumps, propellers)

4.      Torque inversely proportional to speed

(Ex-milling and boring, machines)

2. Different type of industrial loads

There are three types of industrial loads under which electric motors are required to work. they are

v        Continuous load

                        Intermittent load

                        Variable or fluctuating load

            Continuous load

                    Load is continuous in nature

                    Ex- Pumps or fans require a constant power input to keep them operating.

Ø        Intermittent load

                    This type classified in to two types

                    Motor loaded for short time and then shunt off for sufficiently longer duration temperature is brought to the room temperature

Eg: kitchen mixie.

                    The electrical loss is more due to constant ON/OFF delay period

                    Moor loaded for short time and shunt off for short time .

                    Here the motor cannot be cooled down to the room temperature comparison of the two methods it can be Inferred.

                    The temperature level of motor is not brought to the room temperature.