GETCO Exam Paper (22-07-2015) For eliminating 7th harmonics from generated EMF in alternator the fractional pitch must be 2\3 6\7 7\8 5\6 2\3 6\7 7\8 5\6 ANSWER EXPLANATION DOWNLOAD EXAMIANS APP fractional pitch = Cos( α/2)α is obtain from: (nα/2)=90˚ where n is harmonicα=25.7143˚fractional pitch=6/7
GETCO Exam Paper (22-07-2015) A transformer has negative voltage regulation when its load PF is leading zero unity lagging leading zero unity lagging ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Voltage regulation = ((no load voltage)-(full load voltage)/(no load voltage))VR at leading PF = ((I*R*cosφ)-(I*X*sinφ))/VVR at lagging PF = ((I*R*cosφ)+(I*X*sinφ))/V
GETCO Exam Paper (22-07-2015) In synchronous motor, V-curve is a graph of Armature current Vs power factor Armature current Vs Field current Armature current Vs reactive power Armature current Vs active power Armature current Vs power factor Armature current Vs Field current Armature current Vs reactive power Armature current Vs active power ANSWER EXPLANATION DOWNLOAD EXAMIANS APP v curve: armature current → field currentInverted V curve: power factor → field current
GETCO Exam Paper (22-07-2015) Stray loss is equal to _____ field copper loss & iron loss mechanical loss & iron loss copper loss and iron loss frictional loss & copper loss field copper loss & iron loss mechanical loss & iron loss copper loss and iron loss frictional loss & copper loss ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Answer in official key is “mechanical loss & iron loss ”.Many times stray loss is also considered as total loss actually accured minus calculatable loss. This means loss that can be calculated is known as stray loss.
GETCO Exam Paper (22-07-2015) In a DC motor, back EMF value becomes maximum at _____ 1/2 load 3/4 load full load no load 1/2 load 3/4 load full load no load ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Answer in official key is “1/2 load ”.
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