PYQs Based test 10: Electrical Machines

If the primary line voltage rating is 3.3 kV (Y side) of a 25 kVA, Y-Δ transformer (the per phase turns ratio is 5: 1), then the line current rating of the secondary side (in Ampere) is _________.

A three-phase synchronous motor draws 200 A from the line at unity power factor at rated load. Considering the same line voltage and load, the line current at a power factor of 0.5 leading is

A separately excited dc motor has an armature resistance Rₐ = 0.05 Ω. The field excitation is kept constant. At an armature voltage of 100 V, the motor produces a torque of 500 Nm at zero speed. Neglecting all mechanical losses, the no-load speed of the motor (in radian/s) for an armature voltage of 150 V is _____ (up to 2 decimal places).

Two single – phase transformers T₁ and T₂ each rated at 500 kVA are operated in parallel Percentage impedances of T₁ and T₂ are (1 + j6) and (0.8 + j4.8), respectively. To share a load of 1000 kVA at 0.8 lagging power factor, the contribution of T₂ (in kVA) is _____________

Three single-phase transformers are connected to form a delta-star three-phase transformer of $110kV/11kV$. The transformer supplies at $11kV$ a load of $8MW$ at $0.8p.f.$ lagging to a nearby plant. Neglect the transformer losses. The ratio of phase currents in delta side to star side is