Synchronous Motors

When the stator windings are connected in such a way that the number of poles is made half , then the speed of the rotor of the Synchronous Motor -----------------

• remains same as the original value

• decreases to half the original value

• ends to becomes zero

• increases to two times the original value

The speed of the Synchronous motor

• increases as the load increases

• decreases as the load decreases

• always remains constant

• none of the above

In which of the following motors, the stator and rotor magnetic field rotate at the same speed?

• Universal Motor

• Synchronous Motor

• Induction Motor

• Reluctance Motor

The angle between rotating stator flux and rotor poles is called -------------angle.

• torque

• obtuse

• synchronizing

• powerfactor

The power factor of a synchronous motor is unity when

• the armature current is maximum

• the armature current is minimum

• the armature current is zero

• none of the above

The maximum power developed in a synchronous motor occurs at a coupling angle of

• 30º

• 60º

• 90º

• 180º

For the V curves of a synchronous motor , the graph is drawn between -------------------

• field current and armature current

• terminal voltage and load factor

• power factor and field current

• armature current and power factor

The armature current of the Synchronous Motor has higher values for

• high excitation only

• low excitation only

• both high and low excitations

• none of the options given

An over-excited synchronous motor takes

• leading current

• lagging current

• both leading and lagging currents

• none of the above

In a synchronous motor , the magnitude of stator back emf Eb depends on

• load on the motor

• dc excitation only

• both the speed and rotor flux

• none of the above