Shortly describe about Electric Motor.

2. GROUP INTRODUCTION

3. TOPIC INTRODUCTION
 What is an Electric
Motor?
 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.

4. PRINCIPLE OF HOW MOTORS WORK

5. STRUCTURAL DESIGN
 An electric motor is all about magnets and
magnetism: A motor uses magnets to create
motion.
 A motor is consist of two magnets.

6. SPINNING ARMATURE IN A MOTOR

7. CLASSIFICATION OF MOTORS
Electric Motors
Alternating Current (AC)
Motors
Direct Current (DC)
Motors
Synchronous Induction
Single-Phase Three-Phase
Separately Self Excited
Excited
Series Compound Shunt

8. AC Motors
Alternating Current (AC)
Motors
Synchronous Induction
Single-Phase Three-Phase

9. 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

10. Synchronous Motors
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
Ns = 120 f / P
WHERE,
F = supply frequency
P = number of poles

11. INDUCTION MOTORS
•Induction motors are the most common motors used for
various equipments in industry.
Components
Rotor
• Squirrel cage
•Wound rotor
Stator

12. 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.

13.  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.

14. 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)

15. DC MOTOR
• Main Advantage of DC Motor is-
 Speed control without impact power supply quality
• Changing armature voltage
• Changing field current
 Suitable for turning, spinning, etc.
• Restricted use
• Few low/medium speed applications
• Clean, non-hazardous areas
• Expensive compared to AC motors

16. DC MOTOR
• Relationship between speed, field flux and
armature voltage
Back electromagnetic force: E = KN
Torque: T = KIa
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

17. 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.

18. 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

19. 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

20. 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.

21. EFFICIENCY OF ELECTRIC MOTORS
Factors that influence efficiency
• Age
• Capacity
• Speed
• Type
• Temperature
• Rewinding
• Load

22. 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

23. 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.

24. 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.