
55
3
Common Aspects
ofPower Equipment
All electrical machines have two sets of coils: one set (eld coil in generator and
motor, and primary coil in transformer) produces the working magnetic ux φ and
the other set (armature coil in generator and motor, and secondary coil in trans-
former) reacts to ux φ and produces an electromotive force (voltage) in the gen-
erator and transformer, and a mechanical force (torque) in the motor. Both sets of
coils are embedded in magnetic steel to produce the required ux with a minimum
magnetizing (eld excitation) current. The electromagnetic interaction between two
sets of coils is governed by the ...