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So I am planning on a new shop next year. It has been a LONG time coming so I really hope that nothing expensive interrupts it again! So, in the planning process I need to figure out 3 phase power for a couple of machines I want to add and some that I may replace. So, from all of you electrical types out there, please educate this electrically challenged individual (I can change batteries with very little supervision ) what is the best conversion tool. Are rotary phase converters the best option?

Standing by for some informed advice....thanks!

Shane

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Canada

Shane:
The rotary converters are the only realistic option. They will withstand some abuse, they are stone cold reliable, and pricewise are the only option. You're gonna need a big one to handle your machinery and the solid state ones in your size are very expensive. One the down side, they are less efficient, and make a little noise, you also have to turn them off when not needed 'cause they whine a little (like children). PM me if you need help sizeing and installing. Good luck......... Mikey

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The Biggest Little City, Nevada
www.hammondguitars.com
I love building guitars!

Shane--I'm from the VFD school and am sold on their advantages in the 3HP and less motor sizes.
I've not used anything larger however.
I like the VFD's because of variable speed and reversing, braking etc.
They take up very little space on the wall and can use single phase input to run a three phase motor.
What size motors are we talking for your shop?
Nelson

Is your shop at home or in a commercial complex? If #1, then probably the phase converter is the way to go, unless you just happen to have a 3 phase line running nearby. Check with your power company.
I have a rotary phase converter for the wide belt sander, but it's my only 3PH machine. If I recall, it's on a dedicated 100A, 220V line. There is a large, fused switch box to energize the converter, then a second fused switch lever to send the 3PH to the sander. If you'd like I can send you some photos of the set up and the actual power requirements into the converter and the 3PH output.
If you are only going to run one machine at a time, you could size the 3PH converter for the largest machine and have several circuits switched from it.
If #2, then there may be 3PH very close by and still an economic choice. Wiring the building for it would allow multiple machines to run at the same time, so your "assistants" don't have to stand around waiting for power.

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Hank Mauel

Shane,

This is going into the way back machine a bit. I set up a machine shop in my garage in '78 and initally started with static converters. What I remember is that if you are turning a machine off and on, or changing directions alot, they would kick off. It was also one converter per machine which, as time went by, started to run into a few converters. It did not take long for me to make my own rotary converter. Basically it was a 7.5 hp 3 phase motor that was started with a static converter and once started generated its' own 3 phase power that I could draw off of and run several machines at one time. The 7.5 hp ran real quiet since it wasn't under load and I could easily run 5hp worth of machinery at one time without any limitations. Not that hard to do and somewhere I probably have a schematic of what I did if that helps you out. IMHO static converters, while they do work, always leave you wanting for more. Rotary works.

Tim

I also like VFDs for the reasons above, but, there is more of a learning curve with them than for RPCs.

VFDs are plentiful on ebay, usually around $100 for a used/working one in the 1-20 hp range.

The VFD's rated amps should be equal to or above the motor's rated amps. Many/most can accept 1-ph or "2-ph" (240V) input, with a 30-50% derating on the output amps (best to check the manual to be sure). So it's good to buy a bigger one if you aren't putting 3-ph in. Be sure you get a ~220V VFD if you only have ~220V input -- they can't stretch from 440.

Newer (within 5-10 years) usually run at higher "carrier frequencies" than the old ones -- net result is the motor makes less noise. The 'vector' type VFDs aren't generally important for woodworking, but they often also use higher carrier freqs.

If it is old, or has been sitting w/o power for more than a year, it's important to "reform" the capacitors in some manner (not very difficult... google has more on it).
http://www.abb-drives.com/stdDrives/Res ... efresh.pdf

Setup involves reading the manual and programming some things like current limit, accel time, remote/local control. A 5 kohm potentiometer is usually used if you want a variable speed knob (or just use the keypad).

Just about all of the brands are good. Favored ones include ABB, Allen Bradley, Reliance, Yaskawa/Magnetek, and many more. On ebay, it helps to search for something other than "VFD" as many people selling them don't realize the best way to advertise them, and those labeled "VFD" get the highest prices. I search using "(drive, inverter, VFD) (company names)", though that gets a lot of irrelevant hits, too. Or look in this category:
http://business.shop.ebay.com/AC-Drives ... Industrial

lots of good info on both VFDs and RPCs here:
http://www.practicalmachinist.com/vb/fo ... nd-11.html

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David Malicky

Phase converters are great for most applications. Even thought it is more efficient, utilities charge more for 3 phase power than for single phase. The only application for which a phase converter isn't appropriate is for variable speed applications such as and for example Grizzley's 3phase buffer with continuously variable speed settings and/or perhaps some of the continuously variable drill presses.

Thanks for the input so far! My plans are to add a wide belt sander once the shop is up (I just don't have space for one now so my double drum will do until then). So I am expecting to have to run from 15 to 25 hp 3ph for that machine. I am also planning on a much larger dust collection system and that will likely be at least 10 hp 3ph. I have a very good friend of mine, one of my mentors in woodworking (and life!) he has a 40 x 100 woodshop and runs a phase converter in his shop and has great success. I was planning on following suit but I want to be sure that newer technology has not made this process obsolete. I do not have 3ph power close by, the closest is about a mile away. I am considering putting 400 Amps in the shop and running at least a 100 Amps of that to the 3ph panel. I have a variable frequency drive on my spindle on my cnc machine and it works great. So I guess I could blend applications as well, use the RPC for things like the wide belt and the dust collector and if I need variable speed on a specific machine then I could run that separately off of a VFD. How does that sound? Does that make things too complicated?

Thanks for the links as well, I have looked through a few of them and will refer back when it is time to get set this all up in a few months.

Shane

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Canada

In that high HP range, you are better off with an RPC than a VFD. It's possible to find VFDs in that range that take 1-ph input, but they are rare used and expensive new. Derating a 3-ph input VFD to get 25 hp out requires a 40hp vfd, and I doubt those would take 1-ph input at all.

I don't know of any issues running both VFDs and RPCs, except that some VFDs want to see tightly regulated input voltages across the phases (which is a challenge for RPCs). So just continue to run your VFD off 1-ph.

400 amps -- if they are running lines for that, you might get a quote for running 460V 3-ph for that mile. Utility co. 3-ph is far better than RPCs or VFDs (except variable speed): no noise, more efficient since no conversion, good sine wave, tight regulation, less complexity, more reliable, etc., and it simplifies later expansion a lot. 460V 3ph pulls far fewer amps than 230V 1-ph, so more efficient and less copper. I've no idea of the cost or your budget, but if you are planning on staying in your shop, it might be worth it for the long run and would certainly be nicer along the way. Just an idea.

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David Malicky

Thanks David,

I think my way is clear, RPC it is! Running a 3ph line in is not a realistic option as the power poles are not set up to install the extra lines and they are likely not tall enough either which would mean replacing them. I can see bills in the six figures!! Running in 400 amps is not uncommon in situations like mine. I have 45 acres that is in an agricultural land reserve which allows for wood processing and there a few shops around that will be set up similiar.

Thanks again for all of the input!

Shane

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Canada

The motor you use as your RPC should be about twice the hp of the motor it is going to drive. Since you drive the converter motor through only two of its three legs, and at 180º rather than 120º phase difference, you lose efficiency to the tune of about 50%. Fortunately used 3 phase motors are relatively cheap, but you're going to need either a 50 and a 20 horse, or one that is 75+.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.