Synchronous motors

81. The rotor copper losses, in a synchronous motor, are met by

d.c. source
armature input
motor input
supply lines

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button" href="https://exam.pscnotes.com/mcq/the-rotor-copper-losses-in-a-synchronous-motor-are-met-by/#more-45724">Detailed SolutionThe rotor copper losses, in a synchronous motor, are met by

82. While starting a synchronous motor by induction motor action, field winding is usually

connected to D.C. supply
short-circuited by low resistance
supply B. short-circuited by low resistance C. kept open-circuited
none of the above

Detailed

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SolutionWhile starting a synchronous motor by induction motor action, field winding is usually

83. The back e.m.f. in the stator of a synchronous motor depends on

number of poles
flux density
rotor speed
rotor excitation

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81.2z"/> Subscribe on YouTube
class="read-more button" href="https://exam.pscnotes.com/mcq/the-back-e-m-f-in-the-stator-of-a-synchronous-motor-depends-on/#more-45131">Detailed SolutionThe back e.m.f. in the stator of a synchronous motor depends on

84. A synchronous motor can develop synchronous torque

when under loaded
while over-excited
only at synchronous speed
below or above synchronous speed

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288 64S117.2 64 74.6 75.5c-23.5 6.3-42 24.9-48.3 48.6-11.4 42.9-11.4 132.3-11.4 132.3s0 89.4 11.4 132.3c6.3 23.7 24.8 41.5 48.3 47.8C117.2 448 288 448 288 448s170.8 0 213.4-11.5c23.5-6.3 42-24.2 48.3-47.8 11.4-42.9 11.4-132.3 11.4-132.3s0-89.4-11.4-132.3zm-317.5 213.5V175.2l142.7 81.2-142.7 81.2z"/> Subscribe on YouTube develop synchronous torque" class="read-more button" href="https://exam.pscnotes.com/mcq/a-synchronous-motor-can-develop-synchronous-torque/#more-45120">Detailed SolutionA synchronous motor can develop synchronous torque

85. The efficiency of a properly designed synchronous motor will usually fall in range

60 to 70%
75 to 80%
85 to 95%
99 to 99.5%

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range" class="read-more button" href="https://exam.pscnotes.com/mcq/the-efficiency-of-a-properly-designed-synchronous-motor-will-usually-fall-in-range/#more-44970">Detailed SolutionThe efficiency of a properly designed synchronous motor will usually fall in range

86. Synchronous motors are generally not self-starting because

the direction of rotation is not fixed
the direction of instantaneous torque reverses after half cycle
startes cannot be used on these machines
starting winding is not provided on the machines

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11.4-42.9 11.4-132.3 11.4-132.3s0-89.4-11.4-132.3zm-317.5 213.5V175.2l142.7 81.2-142.7 81.2z"/> Subscribe on YouTube class="read-more-container">Detailed SolutionSynchronous motors are generally not self-starting because

87. In a 3-phase synchronous motor, the negative phase sequence exists when the motor is

supplied with unbalanced voltage
under-loaded
over-loaded
none of the above

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class="youtube-icon"> Subscribe on YouTube href="https://exam.pscnotes.com/mcq/in-a-3-phase-synchronous-motor-the-negative-phase-sequence-exists-when-the-motor-is/#more-44879">Detailed SolutionIn a 3-phase synchronous motor, the negative phase sequence exists when the motor is

88. When a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way

augments it directly
directly opposes it
cross-magnetises it
none of the above

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213.5V175.2l142.7 81.2-142.7 81.2z"/> Subscribe on YouTube the following way" class="read-more button" href="https://exam.pscnotes.com/mcq/when-a-3-phase-synchronous-generator-is-supplying-a-zero-power-factor-lagging-load-the-armature-field-affects-the-main-field-in-the-following-way/#more-44488">Detailed SolutionWhen a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way

89. The power developed by a synchronous motor will be maximum when the load angle is

zero
45°
90°
120°

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is" class="read-more button" href="https://exam.pscnotes.com/mcq/the-power-developed-by-a-synchronous-motor-will-be-maximum-when-the-load-angle-is/#more-44418">Detailed SolutionThe power developed by a synchronous motor will be maximum when the load angle is

90. To limit the operating temperature an electrical machine should have proper

voltage rating
current rating
power factor
speed

Detailed Solution

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class="screen-reader-text">To limit the operating temperature an electrical machine should have proper
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