Therefore, the field winding carries whole of the load current (armature current). Series wound dc machines – In this type, field winding is connected in series with the armature winding.Self-excited machines can be further classified as – The field flux gradually increases as the induced current starts flowing through the field winding.
TYPES OF MOTOR WINDING PDF GENERATOR
So, initially, current induces in the armature conductors of a dc generator only due to the residual magnetism. A small amount of flux is always present in the poles due to the residual magnetism. In a self-excited type of DC generator, the field winding is energized by the current produced by themselves.
PMDC (permanant magnet DC) motors are popularly used in small toys, e.g. In this type, the stator field flux may also be provided with the help of permanent magnets (such as in permanent magnet DC motors). They are used in laboratories for research work, for accurate speed control of DC motors with Ward-Leonard system and in few other applications where self-excited DC generators are unsatisfactory. Separately excited DC generators are not commonly used because they are relatively expensive due to the requirement of an additional power source or circuitry. That means the field winding is electrically separated from the armature circuit. Separately excited DC machines: In separately excited dc machines, the field winding is supplied from a separate power source.This makes two broad categories of dc machines (i) Separately excited and (ii) Self-excited. DC machines are usually classified on the basis of their field excitation method. Hence, this classification is valid for both: DC generators and DC motors. Each DC machine can act as a generator or a motor.