3/4 HP Bridgeport electrical question

j c · Jul 22, 2021

Do you know if this Bridgeport is single phase or 3 phase? The motor says single but the plug looks like it's 3 phase. There's no vfd or anything on it, just a junction box to the power feed. I read that Bridgeport made some 3/4 HP models that were single phase. I was thinking this was one of them, but the plug threw me off. I will post photos below. I think the plug is a Non-NEMA Four-Blade Turn-Lock Connector, Non-Grounded, 120V AC/208V AC, 20A

Thanks

dana gear · Jul 24, 2021

It's anyone's guess about the twist lock plug, the motor is clearly 220 Volt, single phase.
On single phase applications some times 4 pole plugs are used. two legs are hot 120/120, one leg is common and the 4th ground.
If there was a work light or a readout on the machine that was 120volt then there would need to be a common leg to complete that circuit. the ground of course for safety.

j c · Jul 28, 2021

Thanks a lot. Yeah, there's a power feed, so that must be for the common. I took off that plug and put on a NEMA L14-30 plug and it's working well now off the single phase. The original 1960s power feed works perfectly too which is great.

metalmagpie · Jul 29, 2021

Is that machine fitted with a reversing switch?

j c · Jul 29, 2021

metalmagpie said:
Is that machine fitted with a reversing switch?

Yes it has a reversing switch on the top left. I haven't used reverse yet but I tried it and it works. My powerfeed just seemed to stop working today though, not sure why. The motor runs but it wont engage.

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