Three phase to single

[Michael Handrinos]

I have a question on converting 3 to single phase. Do I have to change out the magnetic switch?

Thanks

Mike

[Eric Keller]

you are putting a single phase motor on? Assuming the rating of the contactor is sufficient, you shouldn't have to change out the contactor, just use 2 of the 3 contacts

[Charles Lent]

The control circuits get power from two of the original 3 phases. If you are now feeding the tool with only single phase power because you are now running the tool with a single phase motor, make certain that the two power wires that you choose also provide the power to the control circuit. These should also include the motor over current protection circuits. (heaters). You can just not hook up any part of the circuit of the third phase if you can arrange everything to use only the two phases to get 240 V single phase.

Charley

[Don Jarvie]

Maybe. Look at the specs for the switch and it should say how big of a single phase motor it will handle. A smaller motor around 1 hp may be ok but 2 and up will require a bigger switch most likely a Size 1.

[Jim Huelskoetter]

Also, if the replacement motor is the same hp, then your amps will increase and require different heaters. You can google for rating info on heaters and switches. I am starting my first project using a magnetic starter, and for a 5hp motor, single phase requires a larger switch than three phase. But maybe you'll be luckier.

[Don Jarvie]

Looking at an old starter and a Size 0 is rated max 2hp at 220 where it's rated 3hp for a 3 phase. eBay is your friend for getting a replacement.

Try to buy a NEMA type prewired that has the right size heaters included. All you will need to do is hook it up to the 2 power lines. If your motor has built in overload protection, I.e., reset button you can skip the heaters.

[Dan Friedrichs]

Depends on what kind of switch.

In general:
1) The single-phase current will be higher than the 3-phase (assuming same power and voltage). Your switch needs to be rated for this.
2) If the switch contains a built-in overcurrent protection device (aka a "heater"), you'll need to wire it correctly for it to work. Here's a diagram you may find helpful: http://www.schneider-electric.co.uk/en/faqs/FA139511/

[Rollie Meyers]

Magnetic starters have a lower HP rating for single phase applications, which may or may not require replacement of the starter when changing from 3Ø to 1Ø.

[Chris Hachet]

Magnetic starters have a lower HP rating for single phase applications, which may or may not require replacement of the starter when changing from 3Ø to 1Ø.

Pretty much this. And actually, I really prefer three phase motors fWIW....