A three-phase synchronous motor with synchronous impedance of  per unit per phase has a static stability limit of 2.5 per unit. The corresponding excitation voltage in per unit is _________(Round off to 2 decimal places).

A star-connected 3-phase, 400 V, 50 kVA, 50 Hz synchronous motor has a synchronous reactance of 1 ohm per phase with negligible armature resistance. The shaft load on the motor is 10 kW while the power factor is 0.8 leading. The loss in the motor is 2 kW. The magnitude of the per phase excitation emf of the motor, in volts, is ___________ (round off to nearest integer).

A Three-phase synchronous motor draws 200 A from the line at unity power factor at rated load. Considering the same line voltage and load, the line current at a power factor of 0.5 leading is.

A 220 V (line), three-phase, Y-connected, synchronous motor has a synchronous impedance of .

The motor draws the rated current of 10 A at 0.8 pf leading. The rms value of line-to-line internal voltage in volts (round off to two decimal places) is _________.

A synchronous motor is connected to an infinite bus at 1.0pu voltage and draws 0.6pu current at unity power factor. Its synchronous reactance is 1.0pu and resistance is negligible.

The excitation voltage (E) and load angle (δ) will respectively be

A synchronous motor is connected to an infinite bus at 1.0pu voltage and draws 0.6pu current at unity power factor. Its synchronous reactance is 1.0pu and resistance is negligible.

Keeping the excitation voltage same, the load on the motor is increased such that the motor current increases by 20%. The operating power factor will become

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 3 phase, 400 V, 5 kW, star connected synchronous motor having an internal reactance of 10Ω is operating at 50% load, unit pf. Now, the excitation is increased by 1%.  What will be the new load in percent, if the power factor is to be kept same? Neglect all losses and consider linear magnetic circuit.

The flux per pole in a synchronous motor with the field circuit ON and the stator disconnected from the supply is found to be 25mWb. When the stator is connected to the rated supply with the field excitation unchanged, the flux per pole in the machine is found to be 20mWb while the motor is running on no load.

Assuming no load losses to be zero, the no load current down by the motor from the supply

A 415 V, 2 poles, 3 phases, 50 Hz, star connected, non-salient pole synchronous motor has synchronous reactance of 2 Ω per phase and negligible stator resistance. At a particular field excitation, it draws 20 A at unity power factor from a 415 V, 3 phase, 50 Hz supply. The mechanical load on the motor is now increased till the stator current is equal to 50A. The field excitation remains unchanged. Determine:

(a) The per phase open circuit voltage

(b) The developed power for the new operating condition and corresponding power factor

A 2300V, 3-phase synchronous motor driving a pump is provided with a line ammeter and a field rheostat. When the rheostat is adjusted such that the ac line current is minimum, the armature reads 8.8A.
(a) What is the power being delivered to the pump, neglecting losses?

(b) How should the rheostat be adjusted so that the motor operates at 0.8 leading power factor?
(c) How many KVARs is the motor supply to the system at this new power factor?

A cylindrical rotor synchronous motor is switched on the supply with its field winding shorted on themselves. It will

During hunting of synchronous motor

Match the items on the right hand side with those on left hand side

(a) Commutation                             (P) Resistive load

(b) V-curves                                     (Q) Inductive load

(c) Freewheeling diode                  (R) Capacitive load

(d) Overlap                                       (S) Inter pole

                                                           (T) Source Inductance

                                                           (U) Synchronous motor

A synchronous motor operates at 0.8 p.f. lagging. If the field current of the motor is continuously increased

Damper winding is provided in a poly-phase synchronous motor in order to