DC MACHINES AND TRANSFORMERS EE205 KTU B MODAL QUESTIONS FOR SECOND YEAR S3 EEE
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
DC MACHINES AND TRANSFORMERS
(Answer All Questions)
1.What is the Role of dummy coils in a wave wound d.c. machine?
2.Why are the brushes given a backward shift in a d.c. motor?
3.Explain the critical resistance of a dc machine.
4.Explain the voltage building up process in a dc shunt generator.
5.Explain the conditions to be satisfied for the parallel operation of d.c generators.
(Answer Any Two Questions)
6.What is Communication ? What are the Methods to improve the Communication?
7.Derive an expression for demagnetizing and cross magnetizing AT/pole.
8.What are the speed control methods in a dc shunt motor?Explain with diagrams.
9.The open circuit characteristics of a dc shunt generator driven at 300 rpm is as follows:
The field resistance is adjusted to 354.5 ohm and the speed is 300 rpm.
Determine the following:
1) Graphically the no-load voltage
2) Critical field resistance
3) Critical speed for the given field resistance
4) Additional resistance inserted in the field circuit to reduce the no-load voltage to 175v.