In the synchronous motor, the rotor copper losses are met by
Right Answer is:
In the synchronous motor, the rotor copper losses are met by DC source.
A synchronous machine is used to convert mechanical energy into electrical energy or vice-versa. While doing so, the whole of input energy does not appear at the output but a part of it is lost in the form of heat in the surroundings. This wasted energy is called losses in the machine. These losses affect the efficiency of the machine.
The various losses occurring in a synchronous machine can be sub-divided as
- Copper losses.
- Iron losses.
- Mechanical losses
- Stray losses
1. Copper losses: The various windings of the synchronous machine such as armature and field winding are made of copper and have some resistance. When current flows through them, there will be power loss proportional to the square of their respective currents. These power losses are called copper losses.
In general, the various copper losses in a synchronous machine are:
(i) Armature copper loss = I2R
(ii) Field winding copper loss = I2fRf
(iii) Brush contact loss = I2Rb
The brush contact loss is generally included in the field winding copper losses.
Copper losses (both stator and field) depend on the load and they are met by a DC source.
- Friction and windage losses do not depend upon the load condition of the machine; They are the function of the speed only, thus for the most synchronous machine they are constant
- The core losses (hysteresis and eddy current losses) depend upon the speed and magnitude of the rotating magnetic field.