Precision drill press motor troubles - Page 1
Forum section: electronics / repair

author: ChristofferB
author_rank: Frequent Contributor
timestamp: December 25, 2016, 05:19:23 pm
content: Hey, and merry new year!I recently, at a flea market, bought a small really hq looking drill press, and I got it for very cheap because the motor didn't work, since it 'blew the fuses'.It's a 3-phase motor, and I assumed it was used as one-phase, and there was no start/run capacitors on it, so I suspect that's what's tripping the breaker rather than an actual winding short. I don't have much experience with mains voltage motor stuff, but I'd like to get it running, before considering getting a 1 phase replacement motor.Here's what I can see:- three phased- one side of each of three coils shorted into star config- no start/run capacitors addedThe coils all measure the same resistance, so I guess there aren't any direct shorts. I don't have a megger, so I can't check the insulation..Now, there's a lot of diagrams out there for motor wiring, but I still seem to find some conflicting info.What would be needed to get this running on a single phase?I know it'd be running at less power, but the chuck only takes like, 4mm drills, and I mainly work in soft metals and plastics, so that's not an issue.It's not a big motor, a tad larger than a can of soda, but it seems to be very high quality, made in Germany, and looks almost new.Thanks in advance,

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 25, 2016, 06:13:33 pm
content: Do a web search on static phase converters. Essentially you need to connect the mains to 2 of the motor connections and use a start cap on the third until the motor is up to speed. Once started it will keep running on single phase unless you load it down so much it drops out of sync.You can also use a VFD, but that's a more expensive solution.Another option is a rotary phase converter, but that's kind of overkill for one little drill press.

author: SeanB
author_rank: Super Contributor
timestamp: December 25, 2016, 06:21:53 pm
content: Manufacturers plate on the motor gives you voltages, frequency and current, and it is possible this is a motor designed for inverter use. A picture or three of the unit, the motor and the manufacturers plate of the motor would help here.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: December 25, 2016, 06:33:11 pm
content: Quote from: PaulAm on December 25, 2016, 06:13:33 pmStatic phase converter's what I was talking about, didn't know the name, though. A lot of designs seem to require two phases, just to be certain, does this also work with one 230V phase and N?Quote from: SeanB on December 25, 2016, 06:21:53 pmYou're right, I'll try to get those out later.

author: Seekonk
author_rank: Super Contributor
timestamp: December 25, 2016, 08:58:06 pm
content: I picked up some new really cheap 1/10 KW converters on ebay cheap. So cheap I bought three of them. They will actually turn 1HP motors with no load. I'd connect two wires to line voltage and a 6uF cap to the third motor wire. Connect that to either of the line powered wires. You can reverse direction by connecting to the other line. This may have been designed to work at higher frequency. If you have a variac or auto transformer, try it at a much lower voltage first. Any motor has a V/f ratio. That may be the reason it blew the fuses. Just what size were these fuses.

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 25, 2016, 09:14:54 pm
content: QuoteA lot of thesemoronsmisinformed uneducatable individuals have no idea what they're talking about and continually confuse a center tapped grounded transformer as something providing 2 phase. In the US you either have single phase or 3 phase if you are industrial. Residential is almost 100% single phase. If a US web site is talking about 2 phase go find another site.I don't know about Denmark; but it sounds like you have 230 single phase. The US distribution is 240 center tapped with the center tap (neutral) grounded. Just ignore the neutral and don't get too complicated. It's really not hard to get it running.230 single phase works fine. For this case you can get away with a momentary push button and a start cap. Use an industrial push button rated for the voltage though. You don't want that switch welding itself closed.The big question is the motor. If it's set up for 240 3ph you should be fine. If it's 480 you'll either need a transformer or you might be able to rewire it internally for 240. Larger motors typically can be set up for different voltages, but that might not be true for your drill press.What's the motor nameplate say?edit: Clarified which phase converter websites I was referring to.

author: Monkeh
author_rank: Super Contributor
timestamp: December 25, 2016, 09:23:43 pm
content: Quote from: PaulAm on December 25, 2016, 09:14:54 pmOP is not from the US. You're not looking much brighter than those you're insulting.

author: tronde
author_rank: Frequent Contributor
timestamp: December 26, 2016, 12:57:01 am
content: Quote from: PaulAm on December 25, 2016, 09:14:54 pm

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 26, 2016, 03:47:31 pm
content: Here's pretty much the last word on building a rotary phase converter:http://www.practicalmachinist.com/FitchWConverter.pdfThe important thing to notice from the diagram is that 2 lines (single phase) come in and a start capacitor is temporarily switched into the motor's 3rd winding to get it running. That's all it takes to get a 3ph motor running on single phase. The rest of the stuff (contactors, run caps, PF correction cap) are to improve safety and performance.Commercial static converters will use a current relay to automatically disconnect the start cap once the motor is running, but it is possible to use a start push button.If you see the names Fitch Williams or Jim Hanrahan associated with an article you're looking at good information.Here's another link:http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

author: EPTech
author_rank: Regular Contributor
timestamp: December 28, 2016, 12:49:12 am
content: Hi There,If you have an asynchronous motor wonly the size of a soda can, I guess it will not be more than 250W. Using a capacitor circuit to have it run on 1 phase will lower the power even more. I doubt you will be able to drill anything at all. My advice is to pick up a 230V, single phase variable frequency drive (VFD). They come very cheap on ebay, especially for such alow power. And you will have the benifit of continuously variable speed control. You probably have a 230/400V motor. a 230V single phase input VFD will give you approximately 3x220V output. So you need to put the motor in delta when using such a drive.