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I want to connect Arduino to 3 phase 10 hp ac motor. I just want basic functionality that is I should be able to turn it on or off using the code. Is it possible to do with 3 phase solid state relay? if yes, can I use 3 relays instead of a 3 phase solid state relay? If no, how to do it?

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  • \$\begingroup\$ I’ve no idea how to connect contractor with relay? \$\endgroup\$ – BHAWESH RAJPAL May 15 at 14:02
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Better use three phase contactor with 230VAC coil. Supply 230V to coil by simple arduino relay.

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Since Arduino is limited to 5VDC (or 3.3) you will need an output to a switching transistor to drive the motor contactor of your choice.

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As Eryk has said you should use a single pole relay with a 5V or 3.3V coil (or switching transistor) to energise a larger mechanical contactor (with a coil voltage of your choice) designed for switching 3 phase loads. You should ensure the contactor's contacts are rated for the KW/hp load you are connecting (minimum 10hp+ in this case). *Use a solid state relay if you wish, but it's probably too expensive to justify depending on your motor application.

If you mean 3 separate relays for switching each motor phase directly, this is not recommended as each phase is switching a significantly large load for a relay, which will more than likely cause it to fail long before an adequately sized contactor will fail.

You may also be wasting 3 outputs on your Arduino for 3 separate control signals compared with one control signal for a contactor. Also there is more chance of one of the relay coils failing. All of these points risk you single phasing the motor, causing damage or injury or both.

Also you MUST provide sufficient short circuit and overcurrent protection for the motor in the form of fuses, an MCB or a motor protector circuit breaker.

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