A 280 V, separately excited DC motor with armature resistance of 1 Ω and constant field excitation drives a load. The load torque is proportional to the speed. The motor draws a current of 30A when running at a speed of 1000 rpm. Neglect frictional losses in the motor. The speed, in rpm, at which the motor will run, if an additional resistance of value 10 Ω is connected in series with the armature, is ___________. (round off the nearest integer).

A separately excited dc motor has an armature resistance. The field excitation is kept constant. At an armature voltage of 100V, 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).

A 200V DC series motor, when operating from rated voltage while driving a certain load, draws 10 A current and runs at 1000r.p.m. The total series resistance is . The magnetic circuit is assumed to be linear. At the same supply voltage, the load torque is increased by 44%. The speed of the motor in r.p.m. (rounded to the nearest integer) is ________

A 220 V, 10 kW, 900 rpm separately excited DC motor has an armature . When the motor operates at rated speed and with rated terminal voltage, the electromagnetic torque developed by the motor is 70 Nm. Neglecting the rotational losses of the machine, the current drawn by the motor from the 220 V supply is

A separately excited DC generator has an armature resistance of 0.1Ω 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 voltages across it reach 25 V?

A separately excited DC motor runs at 1000 rpm on no load when its armature terminals are connected to a 200V DC source and the rated voltage is applied to the field winding. The armature resistance of this motor is 1Ω. The no-load armature current is negligible. With the motor developing its full load torque, the armature voltage is set so that the rotor speed is 500 rpm. When the load torque is reduced to 50% of the full load value under the same armature voltage conditions, the speed rises to 520 rpm. Neglecting the rotational losses, the full load armature current (in Ampere) is ________________.

A DC motor has the following specifications: 10 hp, 37.5A, 230 V; flux/pole = 0.01 Wb, number of poles = 4, number of conductors = 666, number of parallel paths = 2. Armature resistance = 0.267 Ω. The armature reaction is negligible and rotational losses are 600 W. the motor operates from a 230 V DC supply. If the motor runs at 1000 rpm, the output torque produced (in Nm) is ____________.

A 4-pole, separately excited, wave wound DC machine with negligible armature resistance is rated for 230V and 5kW at a speed of 1200 rpm. If the same armature coils are reconnected to form a lap winding, what is rated voltage (in volts) and power (in kW) respectively at 1200 rpm of the reconnected machine if the field circuit is left unchanged?

The no-load speed of a 230 V separately excited dc motor is 1400rpm. 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 ________.

A separately excited DC motor runs at 1500 rpm under no-load with 200 V applied to the armature. The field voltage is maintained at its rated value. The speed of the motor when its delivers a torque of 5Nm is 1400rpm as shown in the figure. The rotational losses and armature reaction are neglected.

The armature resistance of the motor is.

A separately excited DC motor runs at 1500 rpm under no-load with 200 V applied to the armature. The field voltage is maintained at its rated value. The speed of the motor when its delivers a torque of 5Nm is 1400rpm as shown in the figure. The rotational losses and armature reaction are neglected.

For the motor to deliver a torque of 2.5Nm at 1400 rpm. The armature voltage to be applied is

In a DC machine, which of the following statements is true?

Two magnetic poles revolve around a stationary armature carrying two coils as shown in Figure. Consider the instant when the poles are in a position as shown. Identify the correct statement regarding the polarity of the induced EMF at this instant in coil sides and  

In relation to DC machines, match the following and choose the correct combination.

A 8 poles, DC generator has a simplex wave-wound armature containing 32 coils of 6 turns each. Its flux per pole is 0.06 Wb. The machine is running at 250 rpm.  The induced armature voltage is

A 200 V, 2000 rpm, 10A, separately excited dc motor has an armature resistance of 2Ω. Rated dc voltage is applied to both the armature and field winding of the motor. If the armature draws 5A from the source, the torque developed by the motor is

A 230V, 250 rpm, 100A separately excited dc motor has an armature resistance of 0.5Ω, the motor is connected to 230V dc supply and rated dc voltage is applied to the field winding. It is driving a load whose torque speed characteristic is given by 500 − 10ω, where ω is the rotational speed expressed in rad/sec and  is the load torque in Nm. Find the steady state speed at which the motor will drive the load and the rated armature current drawn by it from the source. Neglect the rotational losses of the machine.

A 4 pole dynamo with wave wound armature has 51 slots containing 20 conductors in each slot. The induced EMF is 357 volts and the speed is 8500 rpm. The flux per pole will be

A separately excited d.c. motor has an armature resistance of 0.5 ohm. It runs off a 250V d.c. supply drawing an armature current of 20A at 1500 rpm. The torque developed for an armature current of 10A will be _________________ for the same field current.

A 10 kW, 6 pole, D.C generator develops an EMF of 200V at 1500 rpm. The armature has a lap connected winding. The average flux density over a pole pitch is 0.9 Tesla. The length and diameter of the armature are 0.25m and 0.2m respectively. Calculate

(a) The flux per pole

(b) The total number of active conductors in the armature

(c) The torque developed by the machine when the armature supplies a current of 50A.