A three phase synchronous motor connected to ac mains is running at full load and unity power factor. If its shaft load is reduced by half, with field current held constant, its new power factor will be

A $$100$$ $$kVA$$, $$415V,$$ star connected synchronous machine generates rated open circuit voltage $$415V$$ at a field current of $$15A.$$ The short circuit armature current at a field current of $$10A$$ is equal to the rated armature current. The per unit saturated synchronous reactance is

A $$3$$ phase, $$3$$ stack, variable reluctance stepper motor has $$20$$ poles on each rotor and stator stack. The step angle of this stepper motor is

The dc motor, which can provide zero speed regulation at full load without any controller is