Safe way for two leg control of a 480vac Motor

[ecuinc]

I have a customer who want to use ABB soft starts on a 15hp motor. The problem i have is that these soft starts are two leg control. Is there any code on this installation? I would think you would need a contactor after the soft start. Any ideas.

 

[iwire]

The disconnecting means must break all ungrounded conductors. 430.103 The controller does not have to. 430.84


That being the case as long as you have a 3 pole disconnecting means within sight of the motor you may use a two pole controller.

 

[jim dungar]

What Bob said.

But you will need to provide 3-phase overload protection. This is why these small soft starts are often used in conjunction with a 3-phase manual starter.

 

[weressl]

What Bob said.

But you will need to provide 3-phase overload protection. This is why these small soft starts are often used in conjunction with a 3-phase manual starter.

The OL protection is integral to the SSRV on most models and it is in all three phases, even though only two phases are 'controlled'.

I don't think 15HP can be considered small.

 

[jim dungar]

The OL protection is integral to the SSRV on most models and it is in all three phases, even though only two phases are 'controlled'.

I don't think 15HP can be considered small.

I sold SSRV controllers that only had (2) SCR's. Only two of the motor leads were run to these controllers, so there is no way these could provide three phase OL protection.