The necessary condition for voltage build-up in self excited generator is

The necessary condition for voltage build-up in self excited generator is:

1. Field winding resistance should be less than critical resistance
2. Poles should contain residual flux
3. Field winding should be properly connected to armature winding
4. All of these

Correct answer: 4. All of these

Explanation: The necessary conditions for the voltage build-up process in a self-excited DC generator are as follows:

1. The poles must retain some residual magnetism; without residual magnetism, the voltage build-up process cannot initiate. In such cases, initiation may be achieved by a separate DC source applied to the shunt field when the armature is stationary.
2. The field winding should be correctly connected to the armature winding. If the field connection is reversed, the field flux will counteract the residual flux.
3. The field winding resistance must be lower than the critical resistance. If the field resistance exceeds the critical resistance, voltage build-up will not occur.
4. The generator’s speed must surpass the critical speed. Remedying this situation involves increasing the prime mover speed beyond the critical speed.