MACHINE DESIGN

A Project Report on Industrial Automation 2015
(Design of AC &DC motor and
Transformer)
FROM
G.E MOTORS (PVT) LTD
13/1, G.T Road, Sheoraphuly
Hoogly, Pin- 712223
Designed by
Arijit chattopadhyay
Electrical Engineering, 3rd year
COLLEGE OF ENGINEERING AND
MANAGEMENT,KOLAGHAT

ACKNOWLEDGEMENT
We are highly indebted to Koushik pain
(Director of GE MOTOR) and Tanmoy
Jyoti Bairagi (Training Instructor) & the
workers of G.E Motors for their guidance
and constant supervision as well as for
providing necessary information regarding
the project & also for their support in
completing the project.

CONTENT
DC Motor:
1. Principle of operation DC Machine
2. Construction of DC Motor& Generator
 Main magnetic field
 Lap winding &Wave Winding
 Commutator & Brush
 Insulation(varnish& paper insulation)
 AC Motor:
1. Principle of Operation of AC Motors
2. Direction of induced E.M.F & the
Laws on which the AC Fundamental
depend.
Faraday’s Law,Fleming’s Right-hand Rule,
Lenz’s Law
3. Conducting Material
4. Machine Winding
 Batch winding
 Lap winding
5.Insulation
 Transformer

1. Working Principle and Basic
Characteristics
 Regulation of Transformer
 Transformer Rating
 Efficiency of Transformer
2. Construction
3. Transformer Equivalent Circuit
DC MOTOR
The DC machine that converts electrical power into mechanical power is called
DC motor. basically works on the principle that when a conductorcarrying
current is placed in the magnetic field, mechanical force acts on the current
carrying conductorand as a result conductorstarts rotating in a direction
depending upon the direction of current and the field and is given by Fleming’s
left-hand rule.
DC machines are characterized by their versatility. By means of various
combinations of shunt-, series-, and separately-excited field windings they can
be designed to display a wide variety of volt-ampere or speed-torque
characteristics for both dynamic and steady-state operation. Because of the ease
with which they can be controlled, systems of dc machines have been frequently
used in applications requiring a wide range of motor speeds orprecise control of
motor output. Indecent years, solid-state ac drive system technology has
developed sufficiently that these systems are replacing dc machines in
applications previously associated almost exclusively with dc machines.
However, the versatility of dc machines in combination with the relative
simplicity of their drive systems will insure their continued use in wide variety
of applications.
DC MOTOR

Schematic
diagram of dc
machine
Working Principle of DC Motor: Direct current (DC) motors are
widely used to generate motion in a variety of products. Permanent magnet DC
(direct current) motors are enjoying increasing popularity in applications
requiring compactsize, high torque, high efficiency, and low power
consumption.
In a brushed DC motor, the brushes make mechanical contactwith a set of
electrical contacts provided on a commutator secured to an armature, forming
an electrical circuit between the DC electrical sourceand coil windings on the
armature. As the armature rotates on an axis, the stationary brushes come into
contact with different sections of the rotating commutator.

DC MOTOR
DC SERIES MOTOR DC COMPOUND
MOTOR
DC SHUNT MOTOR
DC SERIES MOTOR : A series DC motor connects the armature and field
windings in series with a common D.C. power source. The motor speed varies
as a non-linear function of load torque and armature current; current is common
to both the stator and rotor yielding current squared (I^2) behavior. A series
motor has very high starting torque and is commonly used for starting high
inertia loads, such as trains, elevators or hoists. This speed/torquecharacteristic
is useful in applications suchas dragline excavators, where the digging tool
moves rapidly when unloaded but slowly when carrying a heavy load.
DC SHUNT MOTOR: A shunt DC motor connects the armature and field
windings in parallel or shunt with a common D.C. power source. This
type of motor has good speed regulation even as the load varies, but does
not have the starting torque of a series DC motor. It is typically used for
industrial, adjustable speed applications, such as machine tools,
winding/unwinding machines.
DC COMPOUND MOTOR: A compound DC motor connects the armature
and fields windings in a shunt and a series combination to give it
characteristics of both a shunt and a series DC motor.[4] This motor is
used when both a high starting torque and good speed regulation is
needed. The motor can be connected in two arrangements: cumulatively
or differentially. Cumulative compound motors connect the series field to
aid the shunt field, which provides higher starting torque but less speed

regulation. Differential compound DC motors have good speed regulation
and are typically operated at constant speed.
Construction of DC Motor:
Main magnetic field system: This kind of magnetic field
system is categorize into two sub parts –
 Stator : A stator is outermost part of a D.C. Motor and it serve
following purposes:
1. . It provide mechanical supportto the machine.
2. It host magnetic field system as magnetic poles of main magnetic field
are mounted on stator
3. Most importantly it provide path to magnetic flux with very small
reluctance.

 Main field system: A permanent magnet is mounted on stator and in
electromagnet field system an Inductor is mounted on poles on stator and
a current is passed through this inductor to producea magnetic field and
in electromagnet field system an Inductor is mounted on poles on stator
and a current is passed through this inductor to producea magnetic field.
 Armature Winding and Supporting System : Basically armature
winding of a DC machine is wound by one of the two methods, lap
winding or wave winding. The difference between these two is merely
due to the end connections and commutator connections of the
conductor.
 Lap Winding : In lap winding, the finishing end of the coil is connected
to a commutator segment and starting end of the following coil.
 Wave Winding: a conductorunder one pole is connected at the back to a
conductorwhich occupies an almost corresponding position under the
next pole which is of oppositepolarity.
 The diagram below will help you to differentiate between lap winding and
wave winding.
A Typical Structure of construction

Commutator and Brush Arrangement: To keep the torque on a DC motor
from reversing every time the coil moves through the plane perpendicular to the
magnetic field, a split-ring device called a commutator is used to reverse the
current at that point. The electrical contacts to the rotating ring are called
"brushes" since copperbrush contacts were used in early motors. Modern
motors normally use spring-loaded carboncontacts, but the historical name for
the contacts has persisted.
Armature Reaction of DC motor: : With no current in armature conductors,
the M.N.A. coincides with G.N.A.However, when current flows in armature
conductors, the combined action of main flux and armature flux shifts the
M.N.A. from G.N.A. In caseof a generator, the M.N.A. is shifted in the
direction of rotation of the machine. In order to achieve sparkless commutation,
the brushes have to be moved along the new M.N.A. Under such a condition,
the armature reaction produces the following two effects:
1. It demagnetizes or weakens the main flux.
2. It cross-magnetizes or distorts the main flux.
Speedcontrol of DC Motor:
We know, back emf of a DC motor Eb is the induced emf due to rotation of the
armature in magnetic field. Thus value of the Eb can be given by the EMF
equation of a DC generator.
Eb = PØNZ
/60A
(where, P= no. of poles, Ø=flux/pole, N=speed in rpm, Z=no. of armature
conductors, A=parallel paths)
Eb can also be given as,
Eb = V- IaRa
thus from above equations N = E
b
60A
/PØZ
but, for a DC motor A, P and Z are constant

N α K E
b/Ø (where, K=constant)
Flux Control Method
Circuit diagram:
Armature Control Method
Circuit Diagram:

DC GENERATORS
VOLTAGES BUILD UP IN DC GENERATOR:
The voltage buildup in a dc shunt generator depends on the presence of a
residual flux in the poles when the generator first starts to turn, an internal
voltage will be generated which is given by
EA = 𝐾𝜑𝑟𝑒𝑠𝜔
This voltage appears at the terminals of the generator. But when this voltage
appears at the terminals, it causes a current to flow in the generator’s field coil.
Note that there is no load connected to the terminals, hence the field current IF
is only current caused by the voltage EA. This field current produces a magneto
motive force in the poles, which increases the flux in them. The increase in flux
causes an increase in EA and so on. This process canbe modelled
mathematically using a differential equation. Since the internal voltage EA, the
flux in the machine and the field current IF change whiles the voltage is
building up,
These quantities should be treated as time-varying variables.
𝐸 = 𝐸( 𝑡), 𝜑 = 𝜑( 𝑡), IF= 𝐼( 𝑡),

Voltage build up dc generator
AC MACHINES
AC machine can be classified in two categories
 Static
 Transformer
 Dynamic
 Induction machine
 Synchronous machine
Transformer
ransformer is a static device comprising coils coupled through a magnetic
medium connecting two ports at different voltage levels in an electrical
system allowing the interchange of electrical energy between the ports in either
direction via magnetic field without any change of frequency.
Transformer – Working Principle: A transformer can be defined as a static
device which helps in the transformation of electric power in one circuit to
electric power of the same frequency in another circuit. The voltage can be
raised or lowered in a circuit, but with a proportional increase or decrease in the
current ratings.
The main principle of operation of a transformer is mutual inductance between
two circuits SSwhich is linked by a common magnetic flux. A basic transformer
T

consists of two coils that are electrically separate and inductive, but are
magnetically linked through a path of reluctance. The working principle of the
transformer can be understood from the figure below.
As shown above the transformer has primary and secondary windings.
The core laminations are joined in the form of strips in between the strips you
can see that there are some narrow gaps right through the cross-sectionof the
core. These staggered joints are said to be ‘imbricated’. Both the coils have high
mutual inductance. A mutual electro-motive force is induced in the transformer
from the alternating flux that is set up in the laminated core, due to the coil that
is connected to a sourceof alternating voltage. Most of the alternating flux
developed by this coil is linked with the other coil and thus produces the mutual
induced electro-motive force. The so produced electro-motive force can be with
the help of Faraday’s laws of electromagnetic induction.
e=M*dI/dt
Transformers are subdivided into two parts by construction:
 Core type transformer: In core-type transformer, the windings are given to
a considerable part of the core. The coils used for this transformer are
form-wound and are of cylindrical type. Such a type of transformer can
be applicable for small sized and large sized transformers. In the small
sized type, the core will be rectangular in shape and the coils used are
cylindrical. The figure below shows the large sized type. You can see that
the round or cylindrical coils are wound in sucha way as to fit over a
cruciform core section. In the case of circular cylindrical coils, they have
a fair advantage of having good mechanical strength. The cylindrical
coils will have different layers and each layer will be insulated from the
other with the help of materials like paper, cloth, micarta board and so on.

The general arrangement of the core-type transformer with respectto the
core is shown below. Both low-voltage (LV) and high voltage (HV)
windings are shown.
 Shell type transformer: In shell-type transformers the coresurrounds a
considerable portion of the windings. The comparison is shown in the
figure below.
The coils are form-wound but are multi layer disc type usually wound in the
form of pancakes. Paper is used to insulate the different layers of the multi-layer
discs. The whole winding consists of discs stacked with insulation spaces
between the coils. These insulation spaces form the horizontal cooling and
insulating ducts. Such a transformer may have the shape of a simple rectangle or
may also have a distributed form

E.M.F Equation of a Transformer:
NA = Number of turns in primary,NB = Number of turns in secondary,Ømax =
Maximum flux in the core in Webbers = Bmax X A, Therefore, average rate
of change of flux = Ømax/ ¼ f = 4f ØmaxWb/s
Therefore, r.m.s value of e.m.f/turn = 1.11 X 4f Ømax = 4.44f Ømax
f = Frequency of alternating current input in hertz (HZ)
Voltage Transformation Ratio (K):
EB/ EA = VB/ VA = NB/NA = K
(1)If NB>NA , that is K>1 , then transformer is called step-up
transformer.
(2) If NB<1, that is K<1 , then transformer is known as step-
down transformer.
Equivalent circuit: Referring to the diagram, a practical transformer's physical
behavior may be represented by an equivalent circuit model, which can
incorporate an ideal transformer.
Winding joule losses and leakage reactance are represented by the following
series loop impedances of the model:

 Primary winding: RP, XP
 Secondarywinding: RS, XS.
In normal courseof circuit equivalence transformation, RS and XS are in
practice usually referred to the primary side by multiplying these
impedances by the turns ratio squared.
( 𝑁𝑝| 𝑁𝑠)2
 Core or iron losses: RC
 Magnetizing reactance: XM.
,
Induction motor
An induction or asynchronous motor is an AC electric motor in which
the electric current in the rotor needed to producetorque is obtained
by electromagnetic induction from the magnetic field of the stator winding. An
induction motor therefore does not require mechanical, separate-excitation or
self-excitation for all or part of the energy transferred from stator to rotor, as in
universal, DC and large synchronous motors. An induction motor's rotor can be
either wound type or squirrel-cage type.
Principles of operation: In both induction and synchronous motors, the AC
power supplied to the motor's stator creates magnetic that rotates in time with
the AC oscillations. Whereas a synchronous motor's rotorturns at the same rate
as the stator field, an induction motor's rotor rotates at a slower speed than the
stator field. The induction motor stator's magnetic field is therefore changing or
rotating relative to the rotor. This induces an opposing current in the induction

motor's rotor, in effect the motor's secondary winding, when the latter is short-
circuited or closed through an external impedance.The rotating magnetic
flux induces currents in the windings of the rotor;] in a manner similar to
currents induced in a transformer's secondary winding(s). The currents in the
rotor windings in turn create magnetic fields in the rotor that react against the
stator field. Due to Lenz's Law, the direction of the magnetic field created will
be such as to opposethe change in current through the rotor windings. The
cause of induced current in the rotor windings is the rotating stator magnetic
field, so to opposethe change in rotor-winding currents the rotor will start to
rotate in the direction of the rotating stator magnetic field. The rotor accelerates
until the magnitude of induced rotor current and torque balances the
applied load. Since rotation at synchronous speed would resultin no
induced rotor current, an induction motor always operates slower
than synchronous speed.The difference,or "slip," between actual and
synchronousspeed varies from about0.5 to 5.0% for standard Design
B torque curve induction motorsThe induction machine's essential
character is that it is created solely by induction instead of being
separatelyexcited as in synchronous orDC machines or beingself-
magnetized as in permanentmagnetmotors.
Construction:
The stator of an induction motor consists of poles carrying supply current to
induce a magnetic field that penetrates the rotor. To optimize the distribution of
the magnetic field, the windings are distributed in slots around the stator, with
the magnetic field having the same number of north and south poles. Induction
motors are most commonly run on single-phase or three-phase power, but two-
phase motors exist; in theory, induction motors can have any number of phases.
Many single-phase motors having two windings can be viewed as two-phase
motors, since a capacitor is used to generate a second power phase 90° from the
single-phase supply and feeds it to the second motor winding. Single-phase

motors require some mechanism to producea rotating field on start-up. Cage
induction motor rotor's conductorbars are typically skewed to reduce noise.
Synchronous Speed:
𝒏𝒔 = ( 𝟏𝟐𝟎 × 𝒇| 𝑷)Rpm (where ns is the synchronous speed and f is the
frequency (50Hz), P is the number of poles)
Slip: ( 𝒏𝒔 − 𝒏𝒓| 𝒏𝒔) (here nr is the rated speed)

Starting: There are three basic types of competing small induction motors:
single-phase split-phase and shaded-pole types, and small polyphase induction
motors.
A single-phase induction motor requires separate starting circuitry to provide a
rotating field to the motor. The normal running windings within such a single-
phase motor can cause the rotor to turn in either direction, so the starting circuit
determines the operating direction.
In certain smaller single-phase motors, starting is done by means of a shaded
pole with a copperwire turn around part of the pole. The current induced in this
turn lags behind the supply current, creating a delayed magnetic field around the
shaded part of the pole face. This imparts sufficient rotational field energy to
start the motor. These motors are typically used in applications suchas desk
fans and record players, as the required starting torque is low, and the low
efficiency is tolerable relative to the reduced costof the motor and starting
method compared to other AC motor designs.
ELECTRIC MOTOR CONTROLS
1) Starting the Motor:
 Across the Line Starting
 Reduced Voltage Starting
2) Motor Protection:

 Overcorrect Protection
 Overload Protection
Direct On Line Starter:
 Different starting methods are employed for starting induction motors
because Induction Motor draws more starting current during starting. To
prevent damage to the windings due to the high starting current flow, we
employ different types of starters.
 The simplest form of motor starter for the induction motor is
the Direct On Line starter. The DOL starter consist a MCCB or Circuit
Breaker, Contactor and an overload relay for protection. Electromagnetic
contactorwhich can be opened by the thermal overload relay under fault
conditions.
 Typically, the contactor will be controlled by separate start and stop
buttons, and an auxiliary contact on the contactoris used, across the start
button, as a hold in contact. I.e. the contactoris electrically latched closed
while the motor is operating.
Wiring Diagramof DOL Starter:

MACHINE DESIGN

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to MACHINE DESIGN

Similar to MACHINE DESIGN (20)

Recently uploaded

Recently uploaded (20)

MACHINE DESIGN