76. The curve for 20 k W is expected to be
77. In a
synchronous motor hunting can be minimized
using damper bars
(B) by using a flywheel
(C) by designing the motor for adequate
(D) by any of the above methods.
three phase 400 V, 50 Hz synchronous motor is working at 50 percent load. In
case an increase in the field current of the motor causes a reduction in the
armature current, it can be concluded that
motor is delivering reactive power to the mains
motor is absorbing reactive power to the mains
(C) the motor is neither absorbing nor
delivering reactive power.
V-curves for a synchronous motor show
of power factor with dc field current when load on the motor remains constant
of field current and supply voltage when excitation remains constant
of power factor and supply voltage when motor is hunting
of the above.
armature current of the synchronous motor has large values for
low and high excitation.
which range the cost of a synchronous motor can be comparable to the cost of a
induction motor ?
HP high speed
(B) High HP low speed
HP high speed
HP low speed.
resistance test on synchronous motor can be conducted to measure which of the
following resistances ?
(A) Stator winding to
(B) Rotor winding to
(C) Phase to phase winding resistance
(D) All of the above.
curve represents the open circuit characteristic of a synchronous motor
(A) Curve A
(C) Curve C
short circuit test which of the following is short circuited ?
(A) Armature terminals
(B) One of the phase windings of stator
(C) AH phase windings of stator
(D) All phase windings of stator and
duration of sudden short circuit test on a synchronous motor is usually
(A) about one second
(B) about one minute
(C) about one hour
(D) 40 minutes.
maximum torque which a synchronous will develop at rest for any angular
positions of the rotor, at rated stator supply voltage and frequency, is known
(A) Reluctance torque
(B) Synchronous torque
(C) Locked-rotor torque
(D) Pull up torque.
maximum constant load torque under which a synchronous motor will pull into
synchronism at rated rotor supply voltage and frequency is known as
(A) Synchronous torque
(B) Pull in torque
(C) Pull up torque
(D) Pull out torque.
maximum sustained torque which a synchronous motor will develop at synchronous
speed for 1 mm with rated frequency and rated field current is known as
(A) Pull out torque
(B) Reluctance torque
(C) Synchronous torque
(D) Average torque.
total steady state to drive synchronous motor and the load at synchronous speed
is known as
90. The space angle between the axis of the
stator revolving magnetic field and the rotor-pole axis, both looked and
running at synchronous speed, is known as
reactive power angle.