GETCO Exam Paper (22-07-2015) Calculate torque developed by the 3-phase, 5 HP, 4 pole induction motor runs at 1500 rpm 10 N-m 23.5 N-m 0 N-m 22 N-m 10 N-m 23.5 N-m 0 N-m 22 N-m ANSWER EXPLANATION DOWNLOAD EXAMIANS APP P = 2πTN/60 where N is speed in rpm
GETCO Exam Paper (22-07-2015) Which of the following breaking method save energy? plugging dynamic breaking resistor breaking regenerative breaking plugging dynamic breaking resistor breaking regenerative breaking ANSWER EXPLANATION DOWNLOAD EXAMIANS APP three types of electric breaking:Regenerative breaking( leads to economic and energy consevation)pugging (more efficient method of breaking)rheostatic breaking
GETCO Exam Paper (22-07-2015) For eliminating 7th harmonics from generated EMF in alternator the fractional pitch must be 5\6 2\3 7\8 6\7 5\6 2\3 7\8 6\7 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 zero lagging unity leading zero lagging unity leading 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 active power Armature current Vs Field current Armature current Vs power factor Armature current Vs reactive power Armature current Vs active power Armature current Vs Field current Armature current Vs power factor Armature current Vs reactive power ANSWER EXPLANATION DOWNLOAD EXAMIANS APP v curve: armature current → field currentInverted V curve: power factor → field current
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