E2 Motors and Motor Starting #3 Contactors and Motor Starters

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 v1.1

Symbols for Contactors Symbols are shown “de-energized” (no power) with contacts “normally open” Coil Contact Single pole Double pole Triple pole 115v 208-230v, 1 208-230v, 3 © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

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 v1.1

Contactor coil “energized” Contacts close Coil Contact Single pole Double pole Triple pole 115v 208-230v, 1 208-230v, 3 © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

Contactor in Motion The following slide is a front view of a contactor © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

Control Circuit energized Contactor Operation Power to Contactor LINE L1 L2 Contacts pull in CONTROL CIRCUIT Control Circuit energized Power to Load T1 T2 LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

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 v1.1

Side View LINE LOAD L1 L2 T1 T2 CONTROL CIRCUIT © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

Magnetic Coil energized Side View LINE Power to Contactor L1 L2 CONTROL CIRCUIT Magnetic Coil energized Contacts pulled in Power to Load T1 T2 LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

Contactor Troubleshooting 1st Test: Check the mechanical linkage Armature must move freely Burned coils can restrict movement © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

Check Coil Linkage LINE LOAD Safety tip: Always use wooden dowel CONTROL CIRCUIT Close Contacts Power to Load T1 T2 LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

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 v1.1

Checking the Contactor Coil LINE L1 L2 Measurableresistance is GOOD CONTROL CIRCUIT Remove wires from coil OHM Coil 0L 0 Ω 123Ω 0Ω = Shorted Infinite Ω = Open T1 T2 LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

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 v1.1

Check Voltage Across Contacts LINE Example: 230 Volt Line 10 Volts across contacts L1 L2 Replace Contactor CONTROL CIRCUIT NOTE: Any voltage reading across contacts can mean contacts are BAD. 10 Zero is good T1 T2 LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

Motor Starter Basically a contactor with overloads © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

Motor Starter Diagram Coil and contacts: Magnetic overloads: Overloads open switches on high current draw Switches are wired in series Any switch that opens will interrupt power to the coil © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

Motor Starter Power In Coil Contacts (inside) Overloads Manual Reset Power Out © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.1

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