basic of control component description.pdf

Basic of classic control component and description

1. Basics of Control Basics of Control
Components Components
INC 100 INC 100 Electrotechnology Electrotechnology
Assist. Prof. Pakorn Assist. Prof. Pakorn Kaewtrakulpong Kaewtrakulpong, Ph.D. , Ph.D.
INC, KMUTT INC, KMUTT

2. Objectives Objectives
„„
State the purpose and general State the purpose and general principles principlesof of control control
components componentsand and circuits circuits
„„
Identify various Identify various symbols symbolswhich represent control which represent control
components components
„„
Read a basic Read a basic line diagram line diagram
„„
Describe the construction and operating principles of Describe the construction and operating principles of
magnetic contactors magnetic contactorsand and control relays control relays

3. Control Loads and Control Loads and
Control Devices Control Devices
„„
The The control load control loadis an electrical device that uses is an electrical device that uses
electrical power. E.g. electrical power. E.g.
„„
Pilot lights, Pilot lights,
„„
relays, and relays, and
„„
Contactors. Contactors.
„„
Control devices Control devicesare used to activate the control load. are used to activate the control load.
E.g. E.g.
„„
Pushbuttons and Pushbuttons and
„„
switches. switches.

4. Electrical Symbols Electrical Symbols
„„
Contact Contact
„„
Switch Switch
„„
Pushbutton Pushbutton
„„
Coil Coil
„„
Overload Relay Overload Relay
„„
Pilot Light Pilot Light
„„
etcetc

5. Contact Contact
„„
used to indicate an used to indicate an open or closed path of open or closed path of
current flow current flow..
„„
require an action to change their require an action to change their state state..
„„
can be can be
„„
Normally Open ( Normally Open (NONO) or ) or
„„
Normally Closed ( Normally Closed (NCNC).).

6. Switch Switch
„„
also used to indicate an also used to indicate an open or closed path of open or closed path of
current flow current flow..
„„
require another device or action to change their require another device or action to change their
state state..
„„
can be can be
„„
Normally Open ( Normally Open (NONO) or ) or
„„
Normally Closed ( Normally Closed (NCNC).).

7. Selector Switch Selector Switch
„„
TwoTwo--position position
„„
Three Three--position position
„„
Etc. Etc.

8. Switch (cont.) Switch (cont.)
„„
Variations of this symbol are used to represent Variations of this symbol are used to represent
„„
limit limitswitches, switches,
„„
foot footswitches, switches,
„„
pressure pressureswitches, switches,
„„
level levelswitches, switches,
„„
temperature temperature--actuated actuated switches, switches,
„„
flow flowswitches, and switches, and
„„
selector selectorswitches. switches.

9. Pushbutton Pushbutton

10. Pushbutton (cont.) Pushbutton (cont.)
„„
2 basic types of pushbuttons: 2 basic types of pushbuttons:
„„
momentary momentary
„„
maintained maintained(latches in place when the button is (latches in place when the button is
pressed.) pressed.)
„„
can be can be
„„
Normally Open ( Normally Open (NONO) or ) or
„„
Normally Closed ( Normally Closed (NCNC).).

11. Pilot Lights Pilot Lights

12. Pilot Light Pilot Light
„„
a small electric light used to indicate a specific a small electric light used to indicate a specific
condition of a circuit. condition of a circuit.
„„
E.g., a red light might be used to indicate a motor is E.g., a red light might be used to indicate a motor is
running. running.
„„
The The letter letterin the center of the pilot light symbol in the center of the pilot light symbol
indicates the indicates the color colorof the light. of the light.

13. Control Relays Control Relays

14. Control Relays (cont.) Control Relays (cont.)
„„
Relays are widely used in Relays are widely used in control circuits control circuits . .
„„
They are used They are used
„„
for switching multiple control circuits and for switching multiple control circuits and
„„
for for controlling light loads controlling light loads e.g. starting coils, pilot e.g. starting coils, pilot
lights, and audible alarms. lights, and audible alarms.

15. Relay Operation Relay Operation

16. Coil Coil
„„
used in used in electromagnetic starters electromagnetic starters , , contactors contactors, and , and
relays relays..
„„
The purpose of The purpose of contactors contactorsand and relays relaysis to open is to open
and close and close associated contacts associated contacts ..
„„
A letter is used to designate the A letter is used to designate the coil coil; the ; the
associated associated contacts contactshave the have the same identifying same identifying
letter letter..

17. Coil (cont.) Coil (cont.)
„„
Associated contacts Associated contactscan be can be
„„
Normally Open ( Normally Open (NONO) or ) or
„„
Normally Closed ( Normally Closed (NCNC).).

18. Coil Example Coil Example

19. Magnetic Contactors Magnetic Contactors

20. Basic Contactor Operation Basic Contactor Operation

21. Magnetic Contactors: Interior Magnetic Contactors: Interior

22. Control Transformers Control Transformers

23. Timing Relays Timing Relays

24. OnOn--Delay, Time Closed Delay, Time Closed

25. OffOff--Delay, Timed Open Delay, Timed Open

26. Line Diagrams Line Diagrams
„„
also referred to as a also referred to as a ladder diagrams ladder diagrams. .
„„
show the show the functional functionalrelationship of relationship of
components and devices in an electrical circuit, components and devices in an electrical circuit,
notnotthe the physical physicalrelationship. relationship.
„„
made up of 2 circuits, made up of 2 circuits,
„„
the the control controlcircuit and circuit and
„„
the the power powercircuit. circuit.

27. Line Diagrams (cont.) Line Diagrams (cont.)
„„
Electrical wires in a line diagram are represented by Electrical wires in a line diagram are represented by
lines. lines.
„„
Control Control--circuit circuitwiring is represented by a wiring is represented by a lighter lighter--weight weight
line and line and power power--circuit circuitwiring is represented by a wiring is represented by a heavier heavier--
weight weightline. line.
„„
A small A small dotdotor node at the intersection of 2 or more or node at the intersection of 2 or more
wires indicates an wires indicates an electrical connection electrical connection ..
„„
Line diagrams are read from Line diagrams are read from left to right left to right ..

28. Example: Power Circuit and Control Example: Power Circuit and Control
Circuit Circuit

29. Connecting Loads and Connecting Loads and
Control Devices Control Devices
„„
Control circuits are made up of control loads Control circuits are made up of control loads
and control devices. and control devices.

30. Line Numbering Line Numbering

31. TwoTwo--Wire Control Wire Control
„„
A two A two--wire control circuit provides wire control circuit provides
lowlow--voltage voltage
release release
but but not not
lowlow--voltage protection voltage protection
. .
„„
lowlow--voltage release voltage release
„„
In the event of a power loss the contactor will In the event of a power loss the contactor will
deenergize deenergize, stopping the motor. , stopping the motor.
„„
However, when power is restored, the motor will However, when power is restored, the motor will
restart without warning if the control device is still restart without warning if the control device is still
closed. closed.

32. TwoTwo--Wire Control (cont.) Wire Control (cont.)
„„
This type of control scheme is used for This type of control scheme is used for remote remote
or or inaccessible inaccessibleinstallations such as water installations such as water --
treatment plants or pumping stations. In these treatment plants or pumping stations. In these
applications it is desirable to have an immediate applications it is desirable to have an immediate
return to service when power is restored. return to service when power is restored.

33. TwoTwo--Wire Control (cont.) Wire Control (cont.)

34. Holding Circuit Holding Circuit
Three Three--Wire Control Wire Control
„„
lowlow--voltage protection voltage protection..
„„
If an overload causes the If an overload causes the ““OLOL””contacts in the control contacts in the control
circuit to open, circuit to open,
„„
the the ““MM””coil is coil is deenergized deenergizedand and
„„
the motor shut down. the motor shut down.
„„
When the overload is cleared, When the overload is cleared,
„„
the motor will not suddenly restart on its own. the motor will not suddenly restart on its own.
„„
An operator must depress the An operator must depress the ““Start Start””button to restart the button to restart the
motor. motor.

35. Holding Circuit Holding Circuit
Three Three--Wire Control (cont Wire Control (cont.).)

36. Interposing a Relay Interposing a Relay
„„
A 24 VAC coil may A 24 VAC coil may notnotbe be strong enough strong enoughto to
operate a operate a large starter large starter. E.g. . E.g.
„„
the electromagnetic coil of the the electromagnetic coil of the ““MM””contactor contactor
selected is rated for selected is rated for 460 VAC 460 VAC. .
„„
The electromagnetic coil of the The electromagnetic coil of the control relay control relay(CR) (CR)
selected is selected is 24 VAC 24 VAC..

37. Interposing a Relay (cont.) Interposing a Relay (cont.)

38. Schematic Diagram Schematic Diagram

39. Wiring Diagram Wiring Diagram

40. Some Simple Motor Control Some Simple Motor Control
Applications Applications
„„
Forward Forward--Reverse Motor Control Reverse Motor Control
„„
Star Star--Delta Motor Delta Motor--Starting Control Starting Control

41. Forward Forward--Reverse Motor Control Reverse Motor Control
e.g. e.g. „„
Jogging circuits Jogging circuits
„„
Reversing Reversing--after after--stop stop
circuits circuits

42. Jogging Circuits Jogging Circuits
using selector
switch
without short-
circuit protection
with short-
circuit protection

43. Reversing Reversing--After After--Stop Circuits Stop Circuits
without short-
circuit protection
with short-
circuit protection

44. Star Star--Delta Motor Delta Motor--Starting Control Starting Control