e2 motors and motor starting #3 contactors and motor starters
TRANSCRIPT
E2 Motors and Motor Starting
#3 Contactors and Motor Starters
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 2
Descriptions of Contactors
• Contactors have the following:– Coil (electro-magnet)– Contacts (switch)– Mechanical linkage (armature)
• Contactor sequence of operation:– Coil is energized– Armature pulls in– Contacts close– Power flows through contacts to the load
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 3
Symbols for ContactorsSymbols are shown “de-energized” (no power)
with contacts “normally open”
Coil
Single pole
Contact
Double pole
Triple pole
115v 208-230v, 1 208-230v, 3
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 4
Visualizing symbols with power on
• The following slide illustrates what happens when the power is turned on
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 5
Contactor coil “energized”
Contacts close
Single pole
Double pole
Triple pole
115v 208-230v, 1 208-230v, 3
Coil Contact
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 6
Contactor in Motion
• The following slide is a front view of a contactor
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 7
Contactor Operation
L1 L2
T1 T2
LINE
LOAD
Power to Contactor
Power to Load
CONTROL CIRCUIT
Contacts pull in
Control Circuit energized
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 8
Contactor Cut-away view
• The side view of a contactor shows how the coil pulls in the armature and closes the contacts
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 9
Side View
L1 L2
T1 T2
LINE
LOAD
CONTROL CIRCUIT
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 10
L1 L2
T1 T2
LINE
LOAD
Power to Contactor
Power to Load
CONTROL CIRCUIT
Contacts pulled in
Magnetic Coil energized
Side View
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 11
Contactor Troubleshooting
• 1st Test: Check the mechanical linkage– Armature must move freely– Burned coils can restrict movement
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Check Coil Linkage
L1 L2
T1 T2
LINE
LOAD
Power to Load
CONTROL CIRCUIT
Close Contacts
Safety tip:Always use wooden dowel
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Contactor Troubleshooting
• 2nd Test: Ohm the contactor coil– 0 ohms means it’s shorted – Infinite ohms (OL) means coil is open– Measurable resistance, coil is good
• Note: If the coil is shorted or open, correct the problem before replacing contactor
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 14
Remove wires
from coil
L1 L2
T1 T2
LOAD
CONTROL CIRCUIT
Checking the Contactor Coil
Measurableresistance is GOOD
OHM Coil123Ω0 Ω
0Ω = Shorted
0L
Infinite Ω = Open
LINE
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 15
Contactor Troubleshooting
• 3rd Test: Check voltage across contacts (voltage must be applied):– 0 volts means contacts are good– Line voltage means contacts are open– Any voltage reading means contacts are
burned
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 16
L1 L2
T1 T2
LINE
LOAD
CONTROL CIRCUIT
Check Voltage Across Contacts
0
Zero is good
NOTE: Any voltage reading across contacts can mean contacts are BAD.
Example:230 Volt Line10 Volts across contacts
10
Replace Contactor
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Motor Starter
• Basically a contactor with overloads
© 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 18
Motor Starter Diagram
Coil and contacts:
Magnetic overloads:
Overloads open switches on high current draw
Switches are wired in seriesAny switch that opens will interrupt power to the coil
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Motor Starter
Power In
Coil
Power Out
Overloads
Manual Reset
Contacts (inside)
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