# How is motor contactor rating determined?

Contents

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 is motor rating calculated?

Multiply the motor voltage by the full-load current. The result is in watts. Divide watts by 1,000 to give kilowatts. For example, 230 volts x 20 amps = 4,600 watts; 4,600 watts divided by 1000 = 4.6 kilowatts.

## What is AC1 and AC3 rating of contactor?

AC-1 – This category applies to all AC loads where the power factor is more than 0.95. … 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.

## How many amps is 3 horsepower?

HP 200 Volts 440-480 Volts
1 4.8 2.1
1.5 6.9 3.0
2 7.8 3.4
3 11 4.8

## What is kW rating of motor?

Motor is rated in kW since it specifies the capacity of the motor to drive its load. It is the active power (kW) that is of interest when a motor drives a load. The motor converts the active power that it draws from the mains into mechanical power that the load consumes/demands.

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## 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 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.

## How do I choose a contactor size?

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 rating?

The choice of contactor is dependant upon many parameters i.e. operating voltage, size of contacts, number of operations, ambient temperature, type of load supplied etc. Loads are categorised into various AC ratings, (AC1, AC2, AC3 etc.) and the higher the AC rating the more inductive the load becomes.