Frequent question: How do you select a contactor for a motor?

How do I choose a motor contactor?

As per above chart:

  1. Type of Contactor = AC7b.
  2. Size of Main Contactor = 100%X Full Load Current (Line).
  3. Size of Main Contactor = 100%x6 = 6 Amp.
  4. Making/Breaking Capacity of Contactor = Value above Chart x Full Load Current (Line).
  5. Making/Breaking Capacity of Contactor = 8×6 = 52 Amp.

How do I choose a contactor size?

Making/Breaking Capacity of Contactor= Value above Chart x Full Load Current (Line). Making/Breaking Capacity of Contactor=1.5×13= 19 Amp. Size of Star Contactor (Starting Condition) = 33%X Full Load Current (Line). Size of Star Contactor =33%x13 = 4 Amp.

How do you size a compressor contactor?

If the compressor is not listed in the table the contactor can always be sized for full voltage starting by selecting a contactor of the next amperage rating larger than the compressors Rated Load Amps (RLA) and then checking the LRA requirements against the rating of the chosen contactor.

Can you oversize a contactor?

A contactor is a glorified switch and the ratings are for its own function. You want to avoid under-sizing a contactor, but you can oversize.

What does AC3 mean on a contactor?

AC-3 – This category applies to squirrel cage motors with breaking during normal running of the motor. On closing, the contactor makes the inrush current, which is about 5 to 7 times the rated full load current of the motor. On opening, the contactor breaks the rated full load current of the motor.

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What is contactor and types?

A contactor is an electrical device which is used for switching an electrical circuit on or off. … Contactors are most commonly used for controlling electric motors. There are various types of contactors, and each type has its own set of features, capabilities, and applications.

Why is DOL starter used up 5 hp?

Direct-on-Line (DOL) Starter

This heavy current reduces as the motor accelerates to its rated speed. … For a large rating motor, ranging from 5 HP to 25 HP, oil immersed DOL starters are used which provides insulation against sparking on contact points and hence increases the life of starter.

How do you check amps on a contactor?

To test a contactor with a multimeter or voltmeter, use the following steps as a guide.

  1. Remove wires from the line. …
  2. Remove wires from the terminal. …
  3. Turn on the control switch. …
  4. Connect the multimeter. …
  5. Test each line. …
  6. Check for a faulty coil connection.
  7. Check voltage. …
  8. Check ohms.

What happens when AC contactor goes bad?

An AC contactor controls the flow of electricity to all parts of the unit. If the contactor is bad, the AC unit will lose its ability to adequately cool the home and may run continuously, even when the thermostat is turned off. … Pitting occurs when the contactor has encountered extreme voltage and heat.

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