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Chapter 01

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35 views

Chapter 01

Uploaded by

Yash Kanojia
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Electrical Machine II

EEEEC11 (3 – 0 – 2)
Semester 4
Chapter 01: Fundamentals of AC machine
winding
• Physical arrangement of windings in stator and cylindrical rotor; slots
for windings; single turn coil - active portion and overhang
• full-pitch coils, concentrated winding, distributed winding, winding
axis
• Air-gap MMF distribution with fixed current through winding
• concentrated and distributed, Sinusoidal distributed winding, winding
distribution factor
Electrical Machine
?
The electromechanical energy conversion process is a reversible one and simple
adjustment of the mechanical shaft and electrical conditions reverses the flow of power as
illustrated in Fig. 1.2. In this mode of operation, the electromechanical device, in general
called the electric machine, is known as the motor and the machine is said to be in the
motoring mode. Under steady speed operation, again TM (motor) = TL(load). Both in
generating and motoring modes, losses occur in the electric machine, but the overall
conversion efficiencies are very high (close to or above 90%).
A transformer is a static device that transforms electric energy from one ac voltage level to
another. It is this device that has made the electric system almost universally ac

Because the principle of rotating ac machines is akin to that of a transformer, these two are always studied together
in a book. Further, since the transformer analogy can be extended to both the ac machine types, the transformer
study usually precedes the machine study.
BASIC PRINCIPLE, TYPES AND CONSTRUCTIONAL FEATURES
OF ELECTRIC MACHINES

There are three basic rotating electric


machine types, namely
• 1. the dc machine,
• 2. the polyphase synchronous
machine (ac), and
• 3. the polyphase induction machine
(ac).

Three materials are mainly used in machine manufacture; steel to conduct magnetic flux, copper
(or aluminium) to conduct electric current and insulation to insulate the voltage induced in
conductors confining currents to them.
All electric machines comprise of two parts: the cylindrical rotating member called the
rotor and the annular stationary member called the stator with the intervening air-gap as
illustrated in Fig. 1.4. The rotor has an axial shaft which is carried on bearings at each end
located in end covers bolted to the stator. The shaft extends out of the end cover usually at
one end and is coupled to either the prime mover or the load.

The stator and rotor are both made of magnetic material


(steel) which conducts the magnetic flux upon which
depends the process of energy conversion
In both dc and synchronous machines, the main field is created by field poles excited with direct
current. The winding on the field poles is called the field winding. The relative motion of the field
past a second winding located in the other member induces emf in it. The winding interchanges
current with the external electric system depending upon the circuit conditions. It is this winding,
called the armature winding, which handles the load power of the machine, while the field
winding consumes a small percentage (0.5% to 2%) of the rated load power. The load dependent
armature current is known as load current.
SIMPLE LOOP IN
A UNIFORM
MAGNETIC
FIELD
1= single layer widing

Coil side per pole per phase

Coil side per pole


Formula

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