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