GROUP INTRODUCTION

TOPIC INTRODUCTION

Electromechanical device that converts electrical

energy to mechanical energy.

Mechanical energy used to e.g.

Rotate pump impeller, fan, blower

Drive compressors

Lift materials

Motors in industry: 70% of electrical load.

What is an Electric

Motor?

PRINCIPLE OF HOW MOTORS WORK

STRUCTURAL DESIGN

An electric motor is all about magnets andmagnetism: A motor uses magnets to create

motion. A motor is consist of two magnets.

SPINNING ARMATURE IN A MOTOR

CLASSIFICATION OF MOTORS

Electric Motors

Alternating Current (AC)

Motors

Direct Current (DC)

Motors

Synchronous Induction

Three-PhaseSingle-Phase

Self ExcitedSeparately

Excited

Series ShuntCompound

AC Motors

Alternating Current (AC)

Motors

Synchronous Induction

Three-PhaseSingle-Phase

AC MOTORS

Electrical current reverses direction

Two parts: stator and rotor

Stator: stationary electrical component

Rotor: rotates the motor shaft

Speed difficult to control

Two types

• Synchronous motor

• Induction motor

stator

rotor

Synchronous Motors

Ns = 120 f / PWHERE,

F = supply frequency

P = number of poles

A synchronous motor is an AC

motor,which runs at constant speed fixed by

frequency of the sysem.

This motor rotates at a synchronous

speed, which is given by the following

equation

INDUCTION MOTORS

•Induction motors are the most common motors used for

various equipments in industry.

Components

Rotor

• Squirrel cage

• Wound rotor

Stator

INDUCTION MOTORS

Induction motors can be classified into two main groups:

single-phase induction motors

three-phase induction motors

Single-phase induction motors:

These only have one stator winding, operate

with a single-phase power supply...

Three –phase induction motors:

They use three sets of stator coils the rotating

magnetic field drags the rotor around with it.

DC MOTORS

DC motors,as the name implies,use a direct unidirectional current sources of electricity :-◦ Batteries◦ DC Power supply

When power is applied, DC motors turn in one direction at a fixed speed.

They are optimized to run at a fixed, usually high RPM.

Torque is highest at the rated speed and lowest at low speeds.

Almost all can be reversed.

Inexpensive and commonly available.

DC MOTOR

DC Motors – Components

• Field pole

• North pole and south pole

• Receive electricity to form

magnetic field

• Armature

• Cylinder between the poles

• Electromagnet when current goes through

• Linked to drive shaft to drive the load

• Commutator

• Overturns current direction in armature

(Direct Industry, 1995)

DC MOTOR

Speed control without impact power supply quality

• Changing armature voltage

• Changing field current

Suitable for turning, spinning, etc.

• Main Advantage of DC Motor is-

• Restricted use

• Few low/medium speed applications

• Clean, non-hazardous areas

• Expensive compared to AC motors

DC MOTOR

• Relationship between speed, field flux and

armature voltage

Back electromagnetic force: E = KN

Torque: T = KIa

E = electromagnetic force developed at armature terminal (volt)

= field flux which is directly proportional to field current

N = speed in RPM (revolutions per minute)

T = electromagnetic torque

Ia = armature current

K = an equation constant

TYPES OF DC MOTOR

• Separately excited DC motor: field current supplied from

a separate force

• Self-excited DC motor:

1. Shunt motor : the field winding (shunt field) is connected in

parallel with the armature winding.

2. Series motor : the field winding (shunt field) is connected in

series with the armature winding.

3. Compound motor : compound motor is a combination of

shunt and series motor.

UNIVERSAL MOTORS

While most motors operate from either AC or DC, some

can operate from either

These are universal motors and resemble series-wound

DC motors, but are designed for both AC and DC

operation

– typically operate at high speed (usually > 10,000 rpm)

– offer high power-to-weight ratio

– ideal for portable equipment such as hand drills and

vacuum cleaners

UNIVERSAL MOTORS

Both DC and AC motors are used

– high-power motors are usually AC, three-phase

– domestic applications often use single-phase induction

motors

– DC motors are useful in control applications

– Either an AC or DC electrical energy source serves as

the input to the motor.

Another two useful motor’s name are :-

◦ DC servo motors

◦ Stepper motors

EFFICIENCY OF ELECTRIC MOTORS

•The efficiency of a motor can be defined as “the

ratio of a motor’s useful power output to its total

power output.”

•Motors convert electrical energy to mechanical

energy to serve a certain load. In this process,

energy is lost as shown in the figure.

EFFICIENCY OF ELECTRIC MOTORS

Factors that influence efficiency

• Age

• Capacity

• Speed

• Type

• Temperature

• Rewinding

• Load

Motor Load

• Motor load is indicator of efficiency

• Equation to determine load:

Load = Pi x HP x 0.7457

= Motor operating efficiency in %

HP = Nameplate rated horse power

Load = Output power as a % of rated power

Pi = Three phase power in kW

APLICATION

There are numerous ways to design a motor, thus there are many different types of motors.

The type of motor chosen for an application depends on the characteristics needed in that application.

These include:◦ How fast you want the object to move,

◦ The weight, size of the object to be moved,

◦ The cost and size of the motor,

◦ The accuracy of position or speed control needed.

APPLICATION

The different types of motors possess different operating characteristics.

◦ Heavy Industrial applications: AC motors.

◦ Mobile robotics & hobby robots: DC motor, DC servo motor and stepper motors.