The document discusses various types of electric motors and their components. It describes the construction and operating principles of 3-phase induction motors, including their squirrel cage and slip ring rotors. It also covers motor nameplates, insulation classes, starting methods like DOL, star-delta, and electronic soft starting. Motor protection devices like circuit breakers, contactors, and thermal overload relays are explained. Finally, the importance of coordination between motor protection devices and upstream protection is discussed.

1. 1
Internal
LV Motor
(Instructor: Islam Alaa El-Din)

2. Motor Types
Electric
Motors
AC Motors DC Motors
Synchronous Induction
Separately
Excited
Self Excited
Shunt Motor
Series Motor
Compound Motor
Single Phase
Three Phase
Single Phase
Three Phase

3. Motoring Action

4. Operating Principle &
Torque-Speed
Characteristic

5. Construction Features of 3-ph IM
• 3-ph induction motor consists of two parts: the stator and the rotor.
• 3-ph induction motor classified according to the rotor type:
- Slip ring (wound rotor)
- Squirrel cage (bar windings)

6. Squirrel Cage Motor
● Used in the majority of industrial applications
● Simple, economical & rugged motor

7. Slip Ring Motor

8. Motor Nameplate
● It gives among others,
information about the following:
❑ Motor rating
❑ Motor supply details
❑ Motor connection details
❑ Motor frame type and
size
❑ Motor rpm
❑ Permissible temperature rise
❑ Motor duty
❑ Enclosure type
❑ Number of poles

9. Motor Insulation
● The insulating material used for the electrical machines are classified
according to the standards as follows,
- Class A:
Cotton, silk, paper, and similar organic materials, impregnated or immersed
in oil and enamel applied wires (Tmax = 105 C)
- Class B:
Mica, asbestos, glass fiber, and similar inorganic materials (Tmax = 130 C)
- Class E:
An intermediate class between A and B
- Class F:
The same as B but with silicone is added (Tmax = 155 C)
- Class H:
The same as F but the insulator is reinforced (Tmax = 180 C)

11. - The first thing to do in an AC motor is to create a rotating field.
- With single phase AC, one can produce a rotating field by generating
two currents that are out of phase using for example a capacitor.
- In the example shown, the two currents are 90 degree out of phase,
so the vertical component of the magnetic field is sinusoidal, while the
horizontal is cosine, as shown. This gives anticlockwise field rotating.
Rotating Field

12. Slip
- If there is no slip the induced emf in the rotor and the developed torque
equal zero
- Ns : Stator rotating field speed,
Nr : Rotor winding speed relative to stator winding,
(Ns-Nr) : Speed of rotor winding relative to stator flux, and
Slip (s) = (Ns-Nr)/Ns

13. Torque Speed C/Cs
- By analysis, it was found that the speed torque C/Cs is as shown

14. Load Types
According to the torque C/Cs the loads are classified as
follows
Linear torque
Volumetric pumps
 Constant torque 90% of
applications
Hoisting
Conveyor belts
 Parabolic torque
Fans
 Hyperbolic torque
Winders unwinders
Machine tools
4
1
2
3
n (rpm)
T (Nm)

15. 􀂃 Age: New motors are more efficient.
􀂃 Capacity: As with most equipment, motor efficiency increases with
the rated capacity.
􀂃 Speed: Higher speed motors are usually more efficient.
􀂃 Type: For example, squirrel cage motors are normally more
efficient than slip-ring motors.
􀂃 Temperature: Totally-enclosed fan-cooled (TEFC) motors are more
efficient than screen protected drip-proof (SPDP) motors.
􀂃 Rewinding of motors can result in reduced efficiency.
􀂃 Load of the motor.
Factors influence motor efficiency:

16. Motor Starting

17. Induction Motor Starting

18. Induction Motor Starting

19. D.O.L.* Start
● The most frequently used method
● The most economical and simple solution
● Non smooth start (not for elevators)
● Large current peaks (5 to 8x In) which limits its
use to power  5.5 kW on the public distribution
system
● The unique start method which does not
reduce motor torque
* Direct On Line

20. D.O.L Start
● Peak starting current = 3 to 8 In
● Peak starting torque = 0.6 to 1.5Tn
● Advantages :
● Simple starter
● Low cost
● High starting torque
● Disadvantages :
● Very high starting current and torque
● Supply must withstand peak current
● Mechanically harsh starting sequence
Typical applications:
Small machines that often starts on full load

21. Star - Delta Start
Star Delta

22. Star - Delta Start

23. ●Peak starting current = 3 to 4 In
●Peak starting torque = 0.2 to 0.5 Tn
- Advantages :
●Simple economic starter
●Good starting torque, current performance
- Disadvantage:
●Low starting torque
●Non adjustable starting parameters
●Break in supply to motor leads to severe transient current
Typical applications:
Machine starting on no load (small centrifugal pumps, fans, etc.)
Star - Delta Start

24. Induction Motor with Star - Delta Start
Is/3
Ts/3
Tr
Is
Star Delta
Ts
I(A)
n (rpm)
T (Nm)
● Is: DOL start current
● Is/3: start current under star connection
● Ts: DOL start torque
● Ts/3: start torque under star connection
● Tr: resistive torque (load)

25. Autotransformer
starting

26. Resistance stator starting

27. Electronic Soft Starting
●Peak starting current = Adjustable, 1.5In to 5In
●Peak starting torque = Adjustable, 0.1 to 0.7 Tn
- Advantages :
●Parameters are fully adjustable.
●Compact.
●Easily adapted to the application.
- Disadvantages :
●Cost
●Can inject transients (harmonics) into the supply
Typical applications:
Machines requiring very smooth starting (centrifugal pumps and fans,
conveyors..)

28. Frequency converter starting

29. Faults (Causes & Effects)

30. Motor Protection
and
Coordination

31. MOTOR PROTECTION
Types of faults
Motor internal
faults
Faults due to
the load
Faults due to
the power
supply

32. Associated functions to Motor Switching
Low voltage distribution
Isolate equipment from electrical supply
Interrupt current through equipment
Protect against human and material damages
Protect motors against overload current effects
ON / OFF loads
Switching
Isolation
Disconnection
Short circuit protection
Overload protection

33. MOTOR PROTECTION FUNCTIONS
11. SHORT CIRCUIT PROTECTION.
A. FUSES
B. CIRCUIT BREAKERS.

34. MOTOR PROTECTION FUNCTIONS
2. OVERLOAD PROTECTION.
A. OVERLOAD RELAYS (thermal or electronic)
B. PTC THERMAL PROBES

35. The load break switch / isolator
●This device has disconnection and isolation capability
●Can be used safely « on load »
●It does not include any protection mechanism
●May be used as an emergency stop button (with yellow
cover and red handle)

36. The Thermal Relay
●Overload is the most common fault on machines
●Overload creates an increase in current drawn by the
load and leads to dangerous overheating of the load.
●Overheating can affect the isolating materials and thus
the lifetime of the motor
●The relay is made of 3 bimetal elements, each being
surrounded by a heating coil carrying its phase current.
●As the motor draws current, the bimetal will bend and the
amount of bending is linked to the level of current
LRD Relay

37. Definition
The class define the tripping time to 7.2 Ir ; the selection is depending to
the nature of the application.
Tripping class
Class 10 4 < Tp <= 10s
Class 20 6 < Tp <= 20s
Class 30 9 < Tp <= 30s

38. The Manual Fused Switch Isolator
●These devices can be operated on load
●Include fuses to provide short circuit protection
●The operation is often made through side
handle
GS1

39. The Magnetic Circuit Breaker
● Device which provides short-circuit protection. It detects and break high
levels of short circuit currents up to the limit of their breaking capacity.
● Has disconnection capability
● Reset after fault can be done manually by operating the rotary switch,
or remotely using optional module
● For relatively low fault currents, the operation of a circuit breaker is
faster than that of fuses
GV2-L

40. The Magnetic Thermal Circuit Breaker
●This circuit breaker includes both magnetic protection
against short circuits, and thermal protection (motor
overload)
●Since it includes all types of protection and has
disconnection capability, it can be used as a motor starter
for simple machines.
●Optional blocks can be added to enable remote reset and
control of the circuit breaker.
GV2-ME

41. The Contactor
●Makes and breaks current on loads – Switching capacity
●Operated remotely using an electromagnet and a
separate control circuit
●When the coil of the electromagnet is energized, the
mobile part of the contactor moves and current can flow
from the supply network to the load.
●Auxiliary contacts are included and moving
simultaneously with the mobile part of the contactor
LC1-D
contactor

42. The Combined Motor Starter
●In 1983, Telemecanique introduced the first device
capable of disconnection, switching and thermal-magnetic
protection : the INTEGRAL
●This type of product offers all motor starting functions in
one product
●Provides total coordination : no contacts welding after
short-circuit, reduced maintenance operation
●TeSys U starter offers embedded communication
capability with field buses and modularity .
Integral
TeSys U

43. Basic Coordination Theory

44. 2h
1h
30min
10min
5min
2min
1min
20s
10s
5s
2s
1s
1 2 3 4 5 6 8 10 17 In
Short-circuit
Normal overload Rotor locked
Current K x Ie
Time
Starting
Overload protection
Short circuit protection
Breaking capacity
of the contactor
Thermal withstand of
overload protection device
without any damage
IT curves of protective devices
Contactors and motor starters
Coordination with short-circuit protection devices
Abnormal Operation

45. Motor
starting
13 x Ir
10 000
T(s)
1 000
100
10
1
0,1
0,0
1
0,001 k x Ir
7,2 x Ir
GV protection
Distribution
line protection
Tripping due
to starting
inrush
Motor circuit breaker & Distribution protection

46. ● Electrodynamics effects of peak current Imax:
● repulsion of contacts
● propagation of electrical arcs
● damage to isolation equipment and deformation of
parts
● Thermal effects l²t:
● fusion of contacts
● generation of electrical arcs
● heat damage to isolation equipment
Effects of a short-circuit on the contactors

47. Behavior of contactor under the effect of non limited
short-circuit currents
The silver contacts becomes
liquid and weld
The energy due to the short-
circuit becomes very high, the
arc becomes important
Repulsion of the contacts,
due to the energy delivered
by the short-circuit

48. The contacts
remain operational
Start of repulsion of contacts
under the effect of the short-
circuit
The energy from the short-
circuit is limited and
repulsion is stopped
Behavior of contactor under the effect of limited
short-circuit currents

49. Coordination type: NO Coordination
GV2ME / RS
LC1
+
Isolation
I>> Protection
Thermal Overload Protection
LC1 breaking capacity (IEC 947-4)
Welding curve of contacts
i
t
Starting Current
GV2 ME/RS Trip curve
Command

50. GV2ME / RS
LC1
+
Isolation
I>> Protection
Thermal Overload Protection
LC1 breaking capacity (IEC 947-4)
Welding curve of contacts
i
t
Starting Current
GV2 ME/RS Trip curve
Command
Coordination type: Coordination Type 1

51. GV2ME / RS
LC1
+
Isolation
I>> Protection
Thermal Overload Protection
LC1 breaking capacity (IEC 947-4)
Welding curve of contacts
i
t
Starting Current
GV2 ME/RS Trip curve
Command
Coordination type: Coordination Type 2

52. breaking capacity (IEC 947-6)
Never Welding
i
t
Starting Current
Isolation
I>> Protection
Thermal Overload Protection
Command
TeSys U
TeSys U Trip curve
Coordination type: Total Coordination

53. Coordination of protective devices
● Without coordination
● The risks are important for the personnel, the physiques and
materials damages can be also important.
● Type 1 coordination
● Without risk for the operator. It is the most standard solution used.
● Before to restarting, the replacement of parts can be necessary.
● Type 2 coordination
● It is the high performance solution. The risk of fusion of contacts is
possible. In this case, the contacts must be easier separated.
● Total coordination, continuity of service
● It is the higher performance solution.
● No damage and no risk of fusion. Once the fault has been fixed, the
motor starter must be able to restart immediately.