Phase converters.

[Brad Seubert]

I'm sure this has been covered many times but I think my question is more specific than I am finding answers to by searching.

I have been looking for a jointer planer combo machine in the 12" range. I recently came across a 20" felder for a decent price that I am considering. It has a three phase 7 1/2 horse motor.

My garage shop has a 60 amp subpanel. Do I even have enough power to run this thing and lights and dust collector?

If I do have enough power what would be the best way to get three phase for that motor? Rotary? Vfd? Where's a good please to buy from. I'd like an idea how much this will cost.

[Brian Backner]

I'n no electrician, but a good rule of thumb for single phase electric motors is 10amps/hp at 120, or 5amps/hp at 240. So, not counting startup surge, you'd need about 35-40 amps of your 60 amp subpanel.

VFD in that size to convert to three phase would be expensive as you'd have to markedly upsize it. A static phase inverter might be a better choice as they're cheap, but you do take a hit in efficiency and loss of hp. A rotary phase convertor would be best though you would need at least a 10hp idler motor and possibly a 15. You might also consider just replacing the existing motor with a single phase one. One that size isn't cheap, though they do show up on CraigsList from time to time. I got a 10hp single phase Baldor for $200 last year, so they can be found.

If you decide to go with a rotary, there are tons of websites all across the web to help in designing/building one (commercial ones can be pricey). I attempted to load a pdf of the Fitch William convertor, but it is too large a file. You can either Google it, or if you PM your email I can send it directly. I also found a PDF on static inverters.

[Dennis Ford]

Starting that motor is likely to be a problem, replacing with a single phase motor would be better IMO if the machine is belt driven. If it is direct drive, consider what you would do if the motor failed.

[Bruce Page]

I have a static converter on my 5hp engine lathe and a 2hp milling machine, both start up just fine. I've been using this setup for over 20 years.

[Paul Murphy]

I have a 7.5hp single phase compressor that required a 60A breaker, so you might be up against the limits of your wiring.

Many VFD's have a "soft start" adjustment, and I've read that there are also "soft starters" for folks already owning a rotary phase converter. In your situation I think without something controlling your inrush current you will overload your 60A panel.
http://www.lselectric.com/soft-start...quency-drives/

Also, the VFD's and phase converters for motors above 3hp climb quickly in price, so look at the complete package price. You should talk your situation over with a specialty business such as these:
http://www.factorymation.com/
http://www.wolfautomation.com/

[Brad Seubert]

That seems to confirm what I thought. It would be pushing the limits of my current electrical system and add a decent dollar amount to get this thing to run on single phase.

Guess I'll keep looking. Thanks guys!

[Allan Speers]

A rotary phase convertor is far better than a static one, as the latter will coast you 1/3 or your horsepower.

Price will be very high, so yes watch CS.

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IMO, the cost of VFD's today makes the thought of a huge RPC a little antiquated. A dedicated VFD offers several advantages:

Only 1 on-off switch

Easy to add E-stops

Soft-start - In your case, this might be a life-saver, since inrush current could cause trouble with your 60a mainbreaker.

Dynamic braking

Motor reverse

Vari-speed

Extra motor overload protection.

Protection from accidental turn on, as with a Mag starter

No need for a GFI outlet.

---------------------------

Go to http://www.factorymation.com for the best prices on the planet. Then call and talk to "Dianne" for lots of extremely good tech advice.



update: I see Paul already beat me to it. Well, it's still all correct !

[Anthony Whitesell]

Since we are talking phase converters, the logical assumption is the supply is 220VAC single phase. As stated the motor in question is 7.5hp 3 phase (voltage not given).

When I was looking for single phase in-three phase out VFDs, I thought I read something about the highest HP VFD available for this application is 2HP. Is there available a 220VAC single phase in-three phase out 7.5HP VFD available?

[David L Morse]

Since we are talking phase converters, the logical assumption is the supply is 220VAC single phase. As stated the motor in question is 7.5hp 3 phase (voltage not given).

When I was looking for single phase in-three phase out VFDs, I thought I read something about the highest HP VFD available for this application is 2HP. Is there available a 220VAC single phase in-three phase out 7.5HP VFD available?

Not cheap, but, yes: http://www.driveswarehouse.com/p-2124-pc1-75.aspx

[Mike Heidrick]

Man a 20" Felder would so be worth a panel upgrade if needed!

[Brad Seubert]

Man a 20" Felder would so be worth a panel upgrade if needed!

I would love to have it....but I would be stretching my budget already just to purchase the machine, and then I would still have to buy a phase converter and upgrade that power to my house. I only have 100amp main coming into my house from the power company. At the time I had the subpanel put in they said 60 amps for the subpanel was about the most they could do from a 100 amp main.

[Bruce Page]

I upgraded to a 200amp panel last year when I had refrigerated air installed. The panel upgrade was $1500. That included running a new 50amp line to my shop sub panel.

[John Lankers]

Check out this site http://www.temcoindustrialpower.com/...duct_Selection
You should be fine, unless there is some other big draw on the panel besides planer and dust collector. I have a 60 Amp sub panel with almost identical power draw and it's all working just fine. Having said that, if you think you can shove a 20" wide oak plank through the planer and hog off a 1/4" think again, just use common sense. You can't compare an air compressor to a planer or table saw, the compressor always has to start under heavy load - the jointer/planer not. Btw. keep the wiring short and heavy.
I'd bend over backwards to get that machine.

[Rick Fisher]

60 amp single phase should be enough to run a 7.5hp PH-3 motor .. 3 phase motors aren't as in-rush sensitive as single phase, and the Felder will ( should ) have a Star - Delta starter.. The initial inrush shouldn't be an issue for a second or so ..

Technically 60 amps should provide you with 34 amps of PH-3 .. but it won't .. so figure 27-28 amps.. A 3 phase 7.5hp motor will draw maybe 20 amps at full load ..

[Brad Seubert]

Check out this site http://www.temcoindustrialpower.com/...duct_Selection
You should be fine, unless there is some other big draw on the panel besides planer and dust collector. I have a 60 Amp sub panel with almost identical power draw and it's all working just fine. Having said that, if you think you can shove a 20" wide oak plank through the planer and hog off a 1/4" think again, just use common sense. You can't compare an air compressor to a planer or table saw, the compressor always has to start under heavy load - the jointer/planer not. Btw. keep the wiring short and heavy.
I'd bend over backwards to get that machine.

So a static converter like this would work? Seems like I am missing something, this seems to cheap?
http://www.temcoindustrialpower.com/...rs/PC0013.html

I have been watching it on craigslist for awhile and have been thinking about making a lowball offer as that is the only way I could afford it. I imagine it is a tough item to sell since its 3 phase, so I was hoping I could get a deal on it.