Electrical Mach...

A separately excited DC machine supplies a load current of 50 A at a terminal voltage of 220 V. its R_a = 0.2 Ω. This machine is run as a motor with the same terminal voltage and current at the same speed. If ϕ_m is the flux when run as a motor and ϕ_g is the flux when run as a generator, the ratio \(\frac{{{\phi }_{m}}}{{{\phi }_{g}}}\) , is

A 1000 hp, 4 pole, 3 phase, 440 V, 50 Hz, Induction motor has a speed of 1440 rpm on full load. The number of cycles of the rotor voltage makes per minutes will be______

A DC series motor has an armature resistance of 0.7 ohm and field resistance of 0.3 ohm. It takes a current of 15 A from a 200 V supply and runs at 800 rpm. The speed at which it will run when connected in series with a 5 ohm resistance and taking the same current at the same supply voltage is _________ (in rpm)

Two single phase transformers rated 1000 kVA and 500 kVA have per unit leakage impedance of (0.01 + j0.04) pu and (0.02 + j0.06) pu respectively. The largest kVA load that can be delivered by the parallel combination of these two transformers without loading any transformer is – (in kVA)

 A 7.5 kW, 400 V, 3-phase, 50 Hz, 6 pole squirrel cage induction motor operates at 4% slip at full load when rated voltage and frequency is applied.

Assuming a linear relationship between torque and slip in the operating region, the no-load speed of the motor when the supply voltage is reduced to half its rated value is ______(in rpm). The no load torque is 6 N.m.

A 6-pole, 400 V, 50 Hz, 3-phase induction motor has a rotor resistance such that the maximum torque occurs at a slip of 0.2. An additional resistance of 0.5 Ω has to be inserted to obtain 75% of the maximum torque at starting. The rotor reactance is _______ (in Ω)

A 1500 kVA, 4-pole, 3-phase, 50 Hz non salient pole synchronous motor of negligible armature resistance having a synchronous reactance of 45 Ω is operating on an infinite bus with its voltage at 6.6 kV, 50 Hz. The synchronizing torque per mechanical degree of rotor displacement at no load is