3 Phase Power & Switch Location

[Brandon Shew]

I just joined the vintage Unisaw club with a 1940’s model with a 5 HP 3 phase motor. (I’ll post the gloat later.) I have a static 3 phase converter left over from a previous endeavor that will work with this saw. I want to mount the converter on the saw cabinet somewhere and I need to install a switch. I haven’t been able to find a nice paddle style or crash bar style 3 phase switch, but there are plenty of single phase switches available that meet my needs so my question is this:

Can I safely put a single phase 220V switch between the wall outlet and the phase converter, or do I need to put the switch between the phase converter and the motor? In other words – is it safe to switch before the phase conversion or do I need to switch after the phase conversion?

[David G Baker]

Brandon,
Don't know about the wall switch but you can get a magnetic low voltage switch that will operate a 3 phase relay. The low voltage switch can be a paddle or crash bar style switch.

[Brandon Shew]

Brandon,
Don't know about the wall switch but you can get a magnetic low voltage switch that will operate a 3 phase relay. The low voltage switch can be a paddle or crash bar style switch.

I don't know why this got moved to the Workshops forum when I was asking about wiring a switch on a power tool (not wiring a building or shop). The switch is NOT going on the wall.

Anyway - I have not seen any 3 phase paddle style switches to mount on the Unisaw.

[William Cummins]

There is no reason not to put a single phase switch before the static "Starter" ( I will not call one a phase converter as that is not what they do).

William...

[Ed Labadie]

The static converter will have to be wired directly into the magnetic starter. The converter only puts out a "blurp" of 3 phase power at motor startup, after that it does nothing.

Ed

[Rob Russell]

I don't know why this got moved to the Workshops forum when I was asking about wiring a switch on a power tool (not wiring a building or shop). The switch is NOT going on the wall.

We are putting ALL electrical posts in the Workshops Forum, whether they relate to building wiring or other electrically related topics.

[Rod Sheridan]

Hi Brandon, if your motor does not have built in thermal protection (unlikely in a 3 phase motor) you will need overload protection for your motor.

The overload protection can be included in a manual push button starter, or preferably in a magnetic starter with an overload relay.

This issue is seperate from running the motor from a phase converter.

I would use a disconnect switch for the phase converter, followed by a mag starter for the 3 phase motor.

Regards, Rod.