## EE6352 EEI 2marks 16marks

Anna University Regulation 2013 ECE EE6352 EEI 2marks 16marks for all 5 units and ECE 3rd SEM EE6352 Electrical Engineering and Instrumentation Short answers, Question Bank are listed down for students to make perfect utilization and score maximum marks with our study materials.

### D.C. MACHINES

#### PART – A

1. What is prime mover?
The basic source of mechanical power which drives the armature of the generator is called prime mover.
2. Give the materials used in machine manufacturing?
There are three main materials used in m/c manufacturing they are steel to conduct magnetic flux copper to conduct electric current insulation.
3. What are factors on which hysteresis loss?
It depends on magnetic flux density, frequency & volume of the material.
4. What is core loss? What is its significance in electric machines?
When a magnetic material undergoes cyclic magnetization, two kinds of power losses occur on it. Hysteresis and eddy current losses are called as core loss. It is important in determining heating, temperature rise, rating & efficiency of transformers, machines & other A.C run magnetic devices.
5. What is eddy current loss?
When a magnetic core carries a time varying flux, voltages are induced in all possible path enclosing flux. Resulting is the production of circulating flux in core. These circulating current do no useful work are known as eddy current and have power loss known as eddy current loss.
6. How hysteresis and eddy current losses are minimized?
Hysteresis loss can be minimized by selecting materials for core such as silicon steel & steel alloys with low hysteresis co-efficient and electrical resistivity. Eddy current losses are minimized by laminating the core.
7. How will you find the direction of emf using Fleming’s right hand rule?
The thumb, forefinger & middle finger of right hand are held so that these fingers are mutually perpendicular to each other, then forefinger gives the direction of the lines of flux, thumb gives the direction of the relative motion of conductor and middle finger gives the direction of the emf induced.
8. How will you find the direction of force produced using Flemings left hand rule?
The thumb, forefinger & middle finger of left hand are held so that these fingers are mutually perpendicular to each other, then forefinger gives the direction of magnetic field, middle finger gives the direction of the current and thumb gives the direction of the force experienced by the conductor.

9. What is the purpose of yoke in d.c machine?

• It acts as a protecting cover for the whole machine and provides mechanical support for the poles.
• It carries magnetic flux produced by the poles

10. What are the types of armature winding?

• Lap winding, A=P,
• Wave winding, A=2.

11. How are armatures windings are classified based on placement of coil inside the armature slots?
Single and double layer winding.
12. Write down the emf equation for d.c.generator?
E=(ФNZ/60)(P/A)V.
p——— no of poles
Z——— Total no of conductor
Ф——— flux per pole
N——— speed in rpm.

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