DC Machines and Transformer Syllabus and Question Bank For Mid Sem Exam

Electrical Engineering Department

Syllabus for Mid Semester of DC Machine and Transformer

SUBJECT CODE: 2130904

Module 2: D.C. Machines:

Working principle, construction and methods of excitation- Armature Winding: Introduction of simplex lap and wave windings. DC generators: EMF equation methods of excitation – separately and self-excited – shunt, series, compound armature reaction – effects of armature reaction - demagnetizing & cross magnetizing ampere-turns – compensating windings – inter poles – commutation –  methods to improve commutation - voltage build-up – no load characteristics- load characteristics – losses and efficiency – power flow diagram –parallel operation – applications of DC generators.

Module 3: Transformers:

Principle, construction and operation of single phase transformers, phasor diagram, equivalent circuit, voltage regulation, losses and efficiency, Testing- Open & short circuit tests, Polarity test, Sumpner’s test, Separation of hysteresis and eddy current losses, Autotransformers-Construction, Principle, Applications and Comparison with two winding transformer

EXAMPLES RELATED TO ABOVE TOPICS

Electrical Engineering Department

 Question Bank: DC Machine and Transformer (3^rd sem Electrical)

SUBJECT CODE: 2130904

C H A P T E R - 2	Sr No.	D.C. Machines:
	1	Justify: Pole shoe section of DC machine is made larger than its body.
	2	Draw and explain characteristics of DC series generator. Also enlist applications of DC series generator.
	3	Define armature reaction. Explain armature reaction effect in DC machine. How it can be minimized?
	4	Explain each part of DC machine with neat sketch.
	5	What is armature reaction? Explain the methods to overcome the adverse effect of the armature reaction.
	6	Explain the load characteristics of DC shunt generator.
	7	What is commutation?
	8	Explain the O.C characteristic of DC shunt Generator, also define the critical resistance & speed from the characteristic.
	9	Write D.C. machine nameplate with significance of each name.
	10	Write Function and location of inter poles and commutating winding in D.C generator.
	11	Give the classification of DC generator.
	12	Mention the parts of a DC machine. Explain the use of any one of them.
	13	What is the function of brushes in DC machine?
	14	Describe various losses in a DC machine and derive the equation of efficiency of DC machine as a motor and as a generator.
	15	Derive the emf equation of a DC generator.
	16	Compare lap and wave winding.
	17	What is the necessity of starter in a DC motor? Name the starters for DC motors.
	18	Discuss retardation test on D.C machine.
	19	Derive the torque equation of a DC motor from first principles.
	20	Explain critical field resistance of d.c. shunt generator with its significance.
	21	Discuss conditions to be satisfied for a self-excited generator to build up voltages.
	22	Derive the expression of armature torque developed in a dc motor using fundamental equation and power equation. Draw the speed-torque characteristics of shunt, series and compound motors.
	23	Numerical on above mention topics
C H A P T E R - 3		Transformers:
	1	Justify: C.T secondary should never be kept open in any circumstances.
	2	Discuss essential and desirable conditions to be satisfied for parallel operation of two single phase transformers.
	3	Explain direct load test on single phase transformer with circuit diagram.
	4	Derive an expression for saving of copper when auto transformer is used compared to Two winding transformer.
	5	Explain direct load test on single phase transformer with circuit diagram.
	6	Explain direct load test on single phase transformer with circuit diagram.
	7	Explain O.C & S.C. test on 1-Φ transformer.
	8	Explain the constructional details of transformer.
	9	Explain the transformer ON-LOAD with vector diagrams
	10	Can DC supply be applied to a transformer?
	11	Draw phasor diagram for no load condition in transformer.
	12	Why transformer rating in KVA?
	13	What is transformation ratio?
	14	Explain Sumpner’s test for testing of a transformer.
	15	Explain the concept of ideal transformer.
	16	Derive the expression for voltage regulation of a transformer on lagging & leading power factor loads.
	17	Briefly describe the principle of operation of a transformer.
	18	Give a comparison of an auto transformer with a two winding transformer.
	19	Define “All day efficiency” and % regulation of transformer.
	20	Derive the equivalent circuit of a single phase transformer and show how it is useful in the analysis of the performance of a transformer.
	21	Derive expression which shows comparison of copper required in auto transformer and two-winding transformer.
	22	Numerical on above mention topics