derated soft starter

[ILCML]

I've got a soft starter rated for 277/480 3PH 3A.

Will using it to start a 208v 3PH motor hurt it or cause it to act any differently?

Also, if I wanted to use it on a single phase motor, would it work since only 2 legs of the 3 phase are controlled anyways?

This is pre-design and obviously I would not use it in real life, I am just researching at this point.

 

[Marke]

Hello ILCML

Theoretically, it is certainly possible to design a soft starter that would allow you to use it on the 208 volts, but with the unit you are considering, you will need to verify this.
The power assembly will not be a problem, but the supply to the electronics may be too low at the lower voltage. It depends what the design range for the control supply is.

No, you can not use a single phase motor on a three phase soft starter. It will almost surely cause issues.
There are single phase soft starters available that can be used.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[goatmeat]

Running it at a lower voltage should not be a problem. As long as it the current ratting is not higher. You may have to make adjustments in the software. Such as changing the nominal voltage rating. If you try to run it single phase and it has electronic protection, it would prob trip on a phase imbalance, or current imbalance, since the CT's are looking for a current reading on all three phases. At 3 amps, you could start the motor across the line, using a contactor or even use a small vfd.

 

[jraef]

As Marke said, it is going to totally depend on the soft starter. Some have their internal control power derived from the line power terminals, so they will not work at a voltage other than what they are designed for. Some require separate control power to be supplied to them, in which case the power through the SCRs becomes irrelevant. Some also have Voltage Monitoring and may require reprogramming to set the thresholds to the proper levels or disable it. So to use it on a lower voltage, it must be one that uses a separate control power source and has no voltage monitoring functions. Even if you can use it however, pay attention to the CURRENT rating, not HP or kW. A 3 A unit is always 3A regardless of voltage.

Generally though, you will not be able to use a 3 phase soft starter on a 1 phase motor application. The SCR gate timing will be different, even on the versions that use SCRs on only 2 of the 3 legs.

JRaef.com
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