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INDEX TOPIC NAME Pg NO

1.GENERATORS AND MOTORS 3 – 5

2. LAWS USED IN GENERATORS AND MOTORS 6

3 .FARADAYS LAW 7 – 9 4. FLEMINGS LAWS 10 - 14

5. LENZ LAW 15 - 16

6. AMPERES LAW 17 - 20

7. MUTUAL AND SELF INDUCTANCE 21 - 22

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BASIC laws

USED IN

ELECTRICAL MACHINES

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DC MACHINES CAN BE CLASSIFIED AS…

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GENERATORS AND MOTORS

WHICH CONVERTS MECHANICAL TO ELECTRICAL ENERGY AND ELECTRICL TO MECH ENERGY

IT IS ELECTRO MECHANICAL CONVERSION DEVICES FOR A VOLTAGE TO BE INDUCED IN A CONDUCTOR 1. A MAGNETIC FIELD 2. RELATIVE MOTION BETWEEN THE CONDUCTOR

AND THE MAGNETIC FIELD STATOR OF A DC MACHINE CONSISTS OF 1. YOLK 2. SALIANT FIXED POLES 3. BEARINGS 4. BRUSHES

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Laws used

• FARADAY’S LAW• FLEMING’S RULES• Lenz law• Ampere’s rules • Mutual and self Induction laws

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FARADAY’S LAW

Faraday,s law states that induced emf is equal to the rate of change

of magnetic flux in the coil

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FLEMING’SLAWS

THEY ARE OF TWO TYPES 1.RIGHT HAND

2.LEFT HAND FLEMING’S RIGHT HAND

RULE :It states that when thumb, forefingere

and middle Fingere are streached mutually perpendicular to each other

then they represents motion, field and current respectively

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Flemings right hand rule used in generator’s

causes:- motion and magnetic field Effect :- electric current

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LEFT HAND THUMB RULE:

When current flows in a wire, and an external magnetic field is applied across that flow, the wire

experiences a force perpendicular both to that field and to the direction of the current flow. A left hand can be held, as shown in the illustration, so as to represent three mutually orthogonal axes on

the thumb, first finger and middle finger. Each finger is then assigned to a quantity (electric

current, magnetic field and mechanical force). The right and left hand are used for generators and

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Used for calculation of different parameters of motors

oThumb - forceoMiddle - flux

oForefingure – current Causes :-electric current and

magnetic fieldEffect :- generates the motion

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LENZ LAW

An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux.

Lenz's law is shown with the minus sign in Faraday's law of induction

,  which indicates that the induced emf and the change in magnetic

flux have opposite signs.

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AMPERE’S LAW

This expression is Ampere's Law:" The integral of B around any closed

mathematical path equals u0 times the current intercepted by the area

spanning the path "

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BY USING AMPERES LAW WE GET THE DIRECT OF FLUX IN THE CONDUCTOR

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MUTUAL AND SELF INDUCTION

These are used in transformers Mutual- and Self-Induction

The changing magnetic field created by one circuit (the primary) can induce a changing voltage and/or current in a second circuit (the secondary).

The mutual inductance, M, of two circuits describes the size of the voltage in the secondary induced by changes in the current of the primary (primary) V(secondary) = - M *

------ : change in I /change in time

The units of mutual inductance are henry, abbreviated "H".

A circuit can create changing magnetic flux through itself, which can induce an opposing voltage in itself. The size of that opposing voltage is

V(opposing) = - L * : change in I /change in time

where L is the self-inductance of the circuit, again measured in henries.

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MUTUAL INDUCTANCE

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THANK YOU

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