Synchronous Motors Objectives Part 06
101 . The overall power factor is 0.895 lagging.
102 . As the load is applied on a synchronous motor its speed does not fall. The load is now supplied by rotor taking new angular position slightly back of its no load position.
103 . The maximum power developed in synchronous motor depends on all supply voltage, rotor excitation and maximum value of coupling angle and does not depend upon direction of rotation.
104 . In a synchronous motor on a fixed excitation when the load is doubled the torque angle ꝕr will be 2ꝕr.
105 . In a synchronous motor the armature current has the highest value when excitation is high and low.
106 . For a synchronous motor the ratio of starting torque / running torque is 0.
107 . Synchronous motors for power factor correction operate at no load and greatly over-excited fields.
108 . The construction of synchronous motor resembles which of the following machines DC shunt generator.
109 . The construction of synchronous motor resembles which of the following machines an alternator.
110 . In a synchronous motor hunting may be due to variation in load, supply voltage, frequency but not due to winding friction.
111 . A synchronous motor is switched on to supply with its field winding short circuited the motor will start as induction motor and run as synchronous motor.
112 . In synchronous motor at no load the armature current is leading the applied voltage by 90o.
113 . In a synchronous motor during hunting when the rotor speed exceeds the synchronous speed damper bars develop induction generator torque.
114 . For a synchronous motor when V is the supply voltage the breakdown torque will be proportional to V2.
115 . When the field winding of an unloaded salient pole synchronous motor is open circuited the motor will stop.
116 . In case one of the 3 phase of synchronous motor is short circuited the motor wil get overheated.
117 . The fact that a synchronous motor with salient pole will operate even if the field current is reduced to zero can be explained by magnetization of rotor poles by stator magnetic field.
118 . The negative phase sequence in a 3-phase synchronous motor exist when the motor is supplied with unbalanced voltage.
119 . The regulation of synchronous motor is 0%.
120 . In a synchronous motor the angle between the rotor poles and stator poles is known as torque angle