Of the total electrical energy generated worldwide, about 58% is used by all motors combined, about 7% for lighting, and the remaining 35% for heating and other uses.
Major types of motor are the synchronous motor, induction motor (also known as asynchronous motor), and dc motor. All have two sets of coils with different currents, say, I1 and I2.
The electromagnetic interaction between two currents produces
motor torque Tm = K I1 I2
If the motor shaft has a load torque TLoad < Tmotor, the motor
would accelerate to a speed at which TLoad = Tmotor, where it would stop accelerating and run at steady speed. The motor armature produces back voltage, or its equivalent, and draws current from the source, which is given by
It is important to understand that the armature draws just enough current that is required to develop torque to meet the load torque at the steady running speed.
Rated load on ship electrical motor
A 100-hp-rated motor does not always deliver full 100 hp regardless of the shaft load.
The motor delivers what is needed to drive the load and draws power from the source equal to what it delivers to the load plus the internal losses. Thus, the power drawn from the source may be less or more than the rated load, depending on the mechanically coupled load on the shaft.
Overload of ship electric motor
However, if continuously overloaded without added cooling, the motor would heat up and burn.
The shaft horsepower, torque, speed, and kW power delivered by the motor are related as follows:
Breakdown of motor types and their energy usage in various horsepower ratings. It shows that about 98% of all motors are induction motors that use
about 93% of the electrical energy used by all motors rated 5 hp and higher. Smaller motors do not use much energy because their use is intermittent, often less than an hour in a day.
