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Need 120v circuit on 3 phase machine

richard newman

Titanium
Joined
Jul 28, 2006
Location
rochester, ny
I have a 5hp 3 phase 20" woodworking bandsaw and would like to have a pair of 120v receptacles on the machine for an LED worklight and a 1/4 hp feed motor. The power feed is DC, with a variable speed controller. I'm thinking to use a 350VA transformer, can get one for less than $50 on ebay. Industrial building 3 phase, not RPC or vfd

Have some ignorant questions to keep me out of trouble:

Can I use a single phases 240v transformer with 2 of the hot legs, or should I use all 3?

Do I need to fuse the transformer? On the input side? How large a fuse?

Is there a better/easier/cheaper way to do this? Want to avoid extension cords or running a 120v circuit from the box.

I'd also like to run a single phase 1-1/2 hp dust collector without ext cord. Can I take 2 hot legs from the feed ahead of the motor controller? 5hp is way overpowered for this saw, never pulls much amperage except at startup. Could I wire the dust collector on the output side of the controller to turn on simultaneously?
 
Single phase as you said.

Yes, fuse it.

Fuse typically 125% of primary rated current. So if 4A, fuse at 5A. Fuse should be a time delay type.

The transformer is the right way, it gets disconnected with everything else when you pull the disconnect for the machine.

Dust collector: If the wires and cords can take the extra current, and it is part of the machine, sure,. I'd put a socket on for it, myself, so it plugs in.
 








 
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