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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 v1.2 2 Symbols for Contactors Symbols are shown “de-energized” (no power) with contacts “normally open” Coil Contact Single pole 115v Double pole 208-230v, 1 © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 Triple pole 208-230v, 3 3 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 4 Contactor coil “energized” Contacts close Coil Contact Single pole 115v Double pole 208-230v, 1 © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 Triple pole 208-230v, 3 5 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 6 Contactor Operation Power to Contactor LINE L1 L2 Contacts pull in CONTROL CIRCUIT Control Circuit energized T1 T2 Power to Load LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 7 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 8 Side View LINE L1 L2 T1 T2 CONTROL CIRCUIT LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 9 Side View LINE L1 Power to L2 Contactor CONTROL CIRCUIT Magnetic Coil energized Contacts pulled in T1 Power to T2 Load LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 10 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 v1.2 11 Check Coil Linkage LINE L1 Safety tip: Always use wooden dowel L2 CONTROL CIRCUIT Close Contacts T1 Power to T2 Load LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 12 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 13 Checking the Contactor Coil LINE L1 L2 CONTROL CIRCUIT Remove wires from coil OHM Coil Measurable resistance is GOOD 123Ω 00LΩ T1 T2 0Ω = Shorted Infinite Ω = Open LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 14 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 15 Check Voltage Across Contacts LINE L1 CONTROL CIRCUIT Example: 230 Volt Line L2 10 Volts across contacts Replace Contactor NOTE: Any voltage reading across contacts can mean contacts are BAD. 0 10 T1 Zero is good T2 LOAD © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 16 Motor Starter • Basically a contactor with overloads © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 17 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 v1.2 18 Motor Starter Power In Coil Contacts (inside) Overloads Manual Reset © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 Power Out 19 © 2005 Refrigeration Training Services - E2#3 Contactors and Motor Starters v1.2 20
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