1
GATE EE 2015 Set 2
+1
-0.3
A 4-pole, separately excited, wave wound DC machine with negligible armature resistance is rated for 230 V and 5 kW at a speed of 1200 rpm. If the same armature coils are reconnected to form a lap winding, what is the rated voltage (in volts) and power (in kW) respectively at 1200 rpm of the reconnected machine if the field circuit is left unchanged?
A
230 and 5
B
115 and 5
C
115 and 2.5
D
230 and 2.5
2
GATE EE 2015 Set 2
Numerical
+1
-0
A shunt-connected DC motor operates at its rated terminal voltage. Its no-load speed is 200 radian/second. At its rated torque of 500 Nm, its speed is 180 radian/second. The motor is used to directly drive a load whose load torque TL depends on its rotational speed $$\omega_r$$ (in radian/second), such that $$T_L=2.78\times\omega_r$$. Neglecting rotational losses, the steady-state speed (in radian/second) of the motor, when it drives this load, is _______.
3
GATE EE 2015 Set 1
+1
-0.3
A separately excited DC generator has an armature resistance of 0.1 $$\Omega$$ and negligible armature inductance. At rated field current and rated rotor speed, its open-circuit voltage is 200 V. When this generator is operated at half the rated speed, with half the rated field current, an un-charged 1000 μF capacitor is suddenly connected across the armature terminals. Assume that the speed remains unchanged during the transient. At what time (in microsecond) after the capacitor is connected will the voltage across it reach 25 V?
A
62.25
B
69.3
C
73.25
D
77.3
4
GATE EE 2014 Set 3
Numerical
+1
-0
The no-load speed of a 230 V separately excited dc motor is 1400 rpm. The armature resistance drop and the brush drop are neglected. The field current is kept constant at rated value. The torque of the motor in Nm for an armature current of 8 A is ____________.