Anna University Previous Year Question Papers for EEE 4th Sem Electrical Machines-I Paper

Anna University Previous Year Question Papers For EEE 4th sem

[1] Define the term synchronous speed [Dec-2003]
For synchronous machines there exists a fixed relationship between number of poles P, frequency (f) and the speed of the machine. The speed of the synchronous machine for the given number of poles and the rated frequency is called the synchronous speed mentioned as NS.

[2] Write an expression for synchronous speed (Dec-2004)
An expression for synchronous speed is NS = 120f/P.
Where
f = frequency
P = No of poles of the machine.

[3] What does speed voltage mean? (Dec-2007)
When the magnetic flux is constant as well as stationary and the coil rotates to cut the flux then EMF gets induced due to relative speed between flux and coil. This EMF is called speed EMF, rotational EMF or dynamically induced EMF.

[4] Mention the factors on which hysteresis loss depends (Dec-2008)
The hysteresis loss is directly proportional to the area under the hysteresis curve ie area of the hysteresis loop.
It is directly proportional to frequency ie number of cycles of magnetization per second.
It is directly proportional to volume of the material.

[5] Distinguish between statically induced and dynamically induced EMF (Dec - 2010, 2011, 2009)
How is EMF induced dynamically ( May-2010)
An induced EMF which is due to physical movement of coil, conductor with respect to flux or movement of magnet with respect to stationary coil, conductor is called dynamically induced EMF or motional induced EMF.
The change in flux lines with respect to coil can be achieved without physically moving the coil or the magnet. Such induced emf in a coil which is without physical movement of coil or a magnet is called statically induced EMF.

[6] Define torque (May-2010)
A turning or a twisting force about an axis is called as torque.

[8] What are the three types of basic rotating electric machines? (May-2011)
DC machines
Induction Machines
Synchronous Machines

[9] What are the causes of core loss? what are the components of core loss?
When a core is subjected to an alternating flux then it undergoes the cycles of magnetisation and demagnetisation. This produces hysteresis effect which causes hysteresis loss in the core.
Similarly core is under the influence of the changing flux and under such condition according to the Faraday's law of electromagnetic induction, EMF gets induced in the core. Such currents in the core which are due to induced emf in the core are called as eddy current loss. Thus eddy current and hysteresis are the two components of the core loss.

Electric Energy Generation Utilisation Interview Questions with Answers

Electric Energy Generation Utilisation Interview Questions & Answers

If you are preparing for a technical interview for a lighting systems related products(LED, Lamps etc) company, then you have landed in a correct page. 

This post will serve to refresh the Lighting concepts, illuminations, related laws and important terms. 

Here we had collected some of frequently asked questions related to illumination. 

In addition to that we had added Anna university previous years questions on EEE 8th sem paper Electric Energy Generation Utilisation [Paper code EE1451]. 

[1] Define luminous flux

It is defined as the total quantity of light energy emitted per second from a luminous body. 

• It is represented by symbol F and is measured in lumens. 
• The conception of luminous flux helps us to specify the output and efficiency of a given light source.

[2] What is meant by luminance?

It is defined as the luminous per unit projected area of either a surface source of light or a reflecting surface and is denoted by L.

[3] What are the laws of illumination?

Law of Inverse squares

Illumination at a point is inversely proportional to square of its distance from the point source and directly proportional to the luminous intensity (CP) of the source of light in that direction.

• If a source of light which emits light equally in all directions be placed at the centre of a hollow sphere, the light will fall uniformly on the inner surface of the sphere. 
• If the sphere be replaced by one of the larger radius, the same total amount of light is spread over a larger area proportional to the square of the radius.

Lamber's cosine law:

The illumination at a point on a surface is proportional to cosine of the angle which ray makes with the normal to the normal to the surface at that point.

[4] What is meant by candle power?

It is defined as the number of lumens given out by the source in a unit solid angle in a given direction. 

It is denoted by CP

Cp = lumens /ω

[5] Define MHCP

The mean of candle power in all directions in the horizontal plane containing the source of light is termed as Mean Horizontal Candle Power

[6] What are all the sources of light?

As per the principle of operation the light sources may be grouped as follows

1. Arc lamps
2. High temperature Lamps
3. Gaseous Discharge Lamps
4. Fluorescent type Lamps

[7] Define utilisation factor

It is defined as the ratio of total lumens reaching the working plane to total lumens given out by the lamp

utilisation factor  = [Total lumens reaching the working plane] / [Total lumens given out by the lamp]

[8] Name the various photometer heads

1. Bunsen head or Grease spot photometer
2. Lummer-brodhun photometer head

There are two types of lummer broadhun heads

• Equality oc Brightness type photometer head
• Contrast type photometer head

[9] What is polar curve?

• In most lamps or sources of light the luminous intensity is not the same in all directions. 
• If the luminous intensity, ie, the candle power is measured in a horizontal plane about a vertical axis and a curve is plotter between candle power and the angular position, a curve obtained is called as horizontal polar curve.
• The luminous intensity in all the directions can be represented by polar curves. 
• If the luminous intensity in a vertical plane is plotted against position, a curve known as vertical polar curve.

[10] Define space-height ratio

It is defined as the ratio of horizontal distance between adjacent lamps and height of their mountings.

Space-height ratio = [Horizontal distance between two adjacent lamps] / [Mounting height of lamps above working plane]

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