Solve the Electrical Engineering (Conventional) Question Paper of 2011 Engineering Services Examination.
2. (a) Expalin No voltage release (NVR) and Over load release (OLR) coils provided in a DC motor starter. 10
(b) A 400 V shunt motor draws 30 A while supplying the rated load at a speed of 120 rad/s. The armature resistance is 1.0 ohm and the field winding resistance is 250 ohms. Detremine the external resistance that must be inserted in series with the armature circuit so that armature current does not exceed 150% of its rated value when the motor is plugged. Find the branking torque at the instant of plugging. 10
(c) A 6600 V/400 V/110 V Satr/Star/Mesh connected three-phase transformer has a magnetizing current of 5.5 A and balanced three-phase load of 1000 kVA at 0.8 lag on secondary and 200 kVA, 0.5 leading power factor load on the tertiary. Find the primary current and power factor. Neglect losses. 20
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