Critical field resistance
Critical field resistance is a term that is associated with a shunt DC generator. In a DC shunt generator, the voltage induced across the armature, Va, is directly proportional to the flux acting across it, The flux in a DC generator is directly proportional to the field current, If. The critical field resistance is defined as the maximum field circuit resistance with which the shunt generator would excite. The shunt generator will build up voltage only if field circuit resistance is less than critical field resistance.
It is a tangent to the open-circuit characteristics of the generator.
