(Govt. of Bihar)CHAPRA(SARAN)

MINOR PROJECT

A Project Report On :-DC Motor Model and Advantages and Disadvantages of AC and DC Motor

Submitted in partial fulfillment of the requirement for in the degree of B. Tech. (Electrical & Electronics Engineering)

Under Guidence Of :- Prof. Vivekanand

Dept. of E.E.E.

L.N.J.P.I.T. Chapra

Submitted By:- NAME COLLEGE ROLL NO. UNIV. ROLL. NO.

1.HARERAM MISHRA 2012-E-28 103157117004

2.PRAKASH KUMAR JHA 2012-E-34 103157117034

3.PAWAN KUMAR 2012-E-68 103157117018

4.RAJMANI SINHA 2012-E-42 103157117061

5.ASHUTOSH KUMAR 2012-E-24 103157117015

6.JAIPRAKASH KUMAR LE-13-E-71 103157117049Dept. Of

Electrical & Electronics EngineeringSession : 2012-2016

Our DC Motor Background

Design Motor

•Design is based on the construction of brush DC Motor.

• There are permanent magnets on the outside and a spinning armature on the inside

•When electricity is put into this electromagnet, it creates a magnetic field in the armature that attracts and repels the magnets in the stator.

•The armature will spin.

Material Used and Cost

Design Motor

TYPE OF MATERIAL COST

1 Wood Block Free

2 Recycle Bottle Free

3 Wire Winding RS 5.00

4 Card Board RS 7.50

5 Permanent Magnet (ceramic)

RS 6.00

6 Car battery (sponsored) Free

7 Soldering Flux Free

TOTAL COST RS 18.50

Design Motor

TYPE OF MOTOR BRUSH MOTOR

NUMBER OF POLE 1

AMOUNT OF VOLTAGE 12V

AMOUNT OF WINDING 20

TYPE OF MAGNET USED Ceramic

Design Motor

IntroductionDC Motor DC motor is an electric motor that runs

on direct current (DC) electricity. Two types of DC motor - brush and brushless DC

Motor. Brushed DC electric motor generates torque

directly from DC power supplied to the motor by using internal commutation, stationary magnets (permanent or electromagnets), and rotating electrical magnets.

Brushless DC motors use a rotating permanent magnet or soft magnetic core in the rotor, and stationary electrical magnets on the motor housing.

AC Motor AC motor is an electric motor driven by

an alternating current. Commonly consists of two basic parts, an

outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the rotating field.

Two main types of AC motors- depending on the type of rotor used.- the asynchronous motor- the synchronous motor

Introduction

Operation of DC Motor

Operation of DC Motor

1.  When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.

2. The armature continues to rotate.3. When the armature becomes horizontally aligned,

the commutator reverses the direction of current through the coil, reversing the magnetic field.

4. The process then repeats.

Advantages of DC MotorOverall advantages that will be discussed are;

1. Provide excellent speed control for acceleration and deceleration.

2. Easy to understand design3. Simple, cheap drive design

Provide excellent speed control- power supply of a DC motor connects directly to the field of the motor allows for precise voltage control, which is necessary with speed and torque control applications. (DC shunt motor)

- The higher the armature voltage, the faster the rotation. This relationship is linear to the motor's maximum speed. (DC series motor)

Advantages of DC Motor

Easy to understand design- The design of the brushed DC motor is quite simple. A permanent magnetic field is created in the stator by either of two means:

Permanent magnets Electro-magnetic windings

- If the field is created by permanent magnets, the motor is said to be a "permanent magnet DC motor" (PMDC).- If created by electromagnetic windings, the motor is often said to be a "shunt wound DC motor" (SWDC). 

Advantages of DC Motor

Advantages of DC Motor Simple and cheap drive design-Varying the speed of a brushed DC motor requires little more than a large enough potentiometer.

-In practice, these have been replaced for all but sub-fractional horsepower applications by the SCR (Silicon Controlled Rectifiers) and PWM (Pulse Width Modulation) drives, which offer relatively precisely control voltage and current.

- Adding an SCR allows simple voltage variability simply by turning the knob and thereby the speed of the motor. 

-Pulse-width modulation is an effective method for adjusting the amount of power delivered to an electrical load

High maintenance- care required to maintain the mechanical interface used to get current to the rotating field.-  maintenance includes the commutator (the collection of copper and mica segments attached to the rotor winding over which the brushes pass), and the brushes themselves.

Not suitable in very clean environment.- vulnerable to dust which decreases performance.

Disadvantages of DC Motor

AC motor has two basic electrical parts: a "stator" and a "rotor“.

Operation of AC Motor

Rotor

Stator

Principle of operation for all AC motors relies on the interaction of a revolving magnetic field created in the stator by AC current, with an opposing magnetic field either induced on the rotor  or  provided  by  a  separate  DC  current  source.

Resulting  interaction  produces  usable torque, which can be coupled to desired loads throughout the facility in a convenient manner.

Operation of AC Motor

Low cost Speed variation High power factor Reliable operation

Advantages of AC Motor

Advantages of AC Motor

Low Cost- Lowest cost motor for applications requiring more than about 1/2 hp (325 watts).- due to the simple design of the motor.- For this reason, AC motors are preferred for fixed speed applications in industrial applications and for commercial and domestic applications where AC line power can be easily attached. - Over 90% of all motors are AC induction motors.- Can be found in air conditioners, washers, dryers, industrial machinery, fans, blowers, vacuum cleaners and many other.

Speed variation - The fixed number of winding sets (known as poles) built into the ac motor, which determines the ac motor's base speed.  - The frequency of the AC line voltage. Variable speed drives (Adjustable speed drives) change this frequency to change the speed of the motor.  - The amount of torque loading on the motor, which causes slip.

Advantages of AC Motor

High power factor- power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit.- a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred.- higher currents increase the energy lost in the distribution system, and require larger wires and other equipment.

Advantages of AC Motor

Reliable Operation- The simple design of the AC motor results in

extremely reliable, low maintenance operation.

- Unlike the DC motor, there are no brushes to replace.

- If run in the appropriate environment for its enclosure, the AC motor can expect to need new bearings after several years of operation. If the application is well designed, an AC motor may not need new bearings for more than a decade.

Advantages of AC Motor

Disadvantages of AC Motor Inability to operate at low

speeds - We know that standard AC motors should not be operated at speeds less than about 1/3 of base speed. This is due to thermal considerations. In fact a DC motor should be considered for these applications. Poor positioning control - Positioning control is expensive and crude with AC motors too. Even a vector drive is very crude when controlling the standard AC motor. - Servo DC motors are more appropriate for these applications.

Disadvantages of AC Motor

AC will produce eddy currents due to the production of a back emf.- Because motors are generators that operate in reverse, they produce an emf just like generators do.- Called as back emf and does not immediately appear when a motor is initially turned on.- The back emf is a consequence of Lenz's law, which states that an induced emf produces a magnetic flux that resists the change.- Back emf works to reduce the current in the loop, thus slowing the motor down, and it gets larger as the speed of the motor increases. 

The advantages and disadvantages of DC and AC motor somehow depends on application used.

• The reference of DC and AC refers how the electrical current is transferred through and from the motor. Both the types of the motors have different functions and applications.

• However, AC motor is widely used in industry application that support AC source voltage.

Conclusion