ELECTRICAL MACHINE
In Electrical engineering , electrical machine is generally refers to machines using electromagnetic force it means electrical machines needed electromagnetic induction to operate and work, such as electrical motor, generators, transformers etc.
Basically if we see rootly then electrical machine are basically electromagnetic energy converter. It changes electromagnetic energy in one form to another. For example. Generators produces Electricity by using mechanical induction and it converts it into electrical energy.
For optimised or practical operations of electrical machines, today's electrical machine are complemented by electronic control.
TYPES OF ELECTRICAL MACHINE
On the basis of movement electrical machine can be categorized in following two types.
1-rotatonary electrical machine.
2-static electrical machine.
On the basis of supply used it can be categorized as follows—
1.AC MACHINE
(EG.INDUCTION MACHINE, SYNCHRONOUS MACHINE)
2-DC MACHINE like DC motor, DC generators. Etc.
On the basis of phase winding it can also be categorized in-
(a) 1-¢ machine
(b) 3-¢machine
DC MACHINE
A DC machine is an electromagnetic conversion devices. There are basically two types of DC machine
1-Dc generators
2-Dc motors
DC GENERATOR
basically the rotating machines consists of two parts-
1- stater parts
2- rotor parts
stator parts- it is one of the most important part of dc machine which consists of following-
1- yoke
2- poles
3- poles-core
4- pole winding
5- pole shoes
6- terminal box
7- brush gair
8- feet or base
rotor parts- it is the part in dc machine from where armature rotates it consist of following-
1- armature
2-armature core
3- armature teeth
4- armature slot
5- armature winding
6- commutator
7- bearings
8- shaft
9- key
10- fan
classification of dc generator-
1- separately excited generators
2- self excited generators
(a) shunt
(b) series
(c) compound
compound machine can be further classified in two parts-
1- shorts shunt compound
2- long shunt compound
Emf Equation of DC Machine
to derive emf equation we have to suppose
¢ =flux per magnetic pole in vebar unit
P= number of poles on stator
n= armature speed in minute
z= total number of slot in conducter= s*c
A= total number of parallel paths
for lap winding a=p
for wave winding
E= induced emf
so total number of flux on poles= ¢ *p wb
total flux cut by per conductor per cycle= ¢*p wb/conductor per revolution
because armature takes one minute to complete n cycle so total mafnetic flux cut by armature conductor in one second= pn/60
acording to farraday law induced emf-
E= emf per conductor/* number of conducter per path
= ¢ pNz/60A volts
hence derived.
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