8/14/2019 Energy conversion(UPTU) DCM/c IEC Assignment

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DEPARTMENT OF ELECTRICAL ENGINEERINGIEC COLLEGE OF ENGINEERING

GREATER NOIDA

TUTORIAL SHEET-1

Instructor: Ramesh Singh Due Date: 16-03-09

1. A 4 pole DC motor is lap wound with 400 conductors, the pole shoe is 20cm longand the average flux density over one pole pitch is 0.4 T, the armature diameter is30cm. Find the torque and gross mechanical power developed when the motor is

drawing 25 a and running at 1500 RPM.

2. A 220 V DC generator supplies 4 KW at a terminal voltage of 220 V, the armatureresistance is 0.4 . If the machine is now operated as a motor at the same terminal

voltage with the same armature current, calculate the ratio of generator speed to

motor speed. Assume that the flux per pole is increased by 10%as the operation is

changed from generator to motor.

3. A DC shunt generator driven by a belt from an engine run at 750 RPM while feeding100 KW of electrical power in to 230 v mains. When the belt breaks it continues torun as a motor drawing 9 KW from the mains. At what speed would it run?

4. A 250 KW, 400 V, 6 pole, DC generator has 720 lap wound conductors. It is given abrush lead of 2.5 angular degrees (mech.) from the geometric neutral. Calculate thecross and demagnetizing turns per pole. Neglect the shunt field current.

5. Calculate the number of conductors on each pole piece required in a compensatingwinding for a 6 pole lap wound DC armature containing 286 conductors. Thecompensating winding carries full armature current. Assume ratio of pole arc to pole

pitch = 0.7.

6. A 440 V, 4 pole, 25 KW, DC generator has a wave connected armature winding with846 conductors.The mean flux density in the air gap under the interpoles is 0.5 Wb

per square meter on full load and the radial gap length is 0.3 cm. calculate the no. of

turns required on each interpole.

7. A compensated Dc machine has 20000 Ampere turns per pole. The ratio of pole arcto pole pitc is 0.8. the interpolar air gap length and the flux density are 1.2 cm and 0.3T respectively. For rated armature current of 1000 A, calculate the compensatingwinding ampere turns per pole and the no. of turns on each interpole.

8. Find the resistance of the load which takes a power of 5 KW from a shunt generatorwhose external characteristics is given by the equation

V = 250 0.5 IL9. A 6 pole DC machine has 300 conductors and each conductor is capable of carrying

80 A without excessive temperature rise. The flux per pole is 0.015Wb and themachine is driven at 1800 RPM. Compute the total current, emf, power developed in

the armature and electromagnetic torque, if the armature conductors are: a) wave

connected b) lap connected.

10. A 24 KW, 250 V, 1500 RPM separately excited DC generator has armature circuitresistance of 0.1. The machine is first run at rated speed and the field current isadjusted to give an open circuit voltage of 260 V. compute terminal voltage of the

generator under these conditions. Field flux remains unaltered.