Replies

1. 
   RickL | Mar 08, 2006 07:20pm | #1

   3 phase motors are simpler and available in larger hp than single phase. I'd contact http://www.phase-a-matic.com and several of the converter companies to get their take on the subject. PAM has some worksheets to size your converter. There's also http://www.phaseperfect.com which is the latest form of converter to come after the VFD. You might need a seperate VFD for each motor. That's a question for the VFD makers and your local motor repair guy. Do you have a local motor shop you can refer to?

   When I had my rotary I found it didn't really consume much power when it was idling.

   
   

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   Edited 3/8/2006 11:33 am ET by RickL

2. 
   JohnWW | Mar 08, 2006 08:11pm | #2

   Kelvin,

   You are talking about serious amperage draw, over 30 horsepower in motors, with either system, and industrial sized machinery.   

   You might want to talk to your power company and find out if they can run three phase to your shop.  You are definitely well beyond the electrical requirements of a typical home shop and, for that matter, the capacity of a typical home electrical system.

   That you would ask a question like this suggests that you don't have experience with purchasing, installing, and using industrial size machinery.  You should probably get some expert advice before you make an investment of this magnitude.

   John White, Shop Manager, Fine Woodworking Magazine

   
   

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   Edited 3/8/2006 12:31 pm ET by JohnWW

1. 
   kelvinpot | Mar 09, 2006 01:40am | #3

   Thanks for the replies. The power company would be the best idea. 3 phase is right on the pole outside of my shop as well. How much does it cost to string it to my shop? $4,500!! Don't like that? Guess thats what happens when monopolies exist. Then you are also labled "commercial" so your rates are higher as well as an additional monthly fees whether you are using it or not. So, i'm hoping to stay within "residential" rates. I just built a new house and had a very heavy line brought in so i have 100 amps just for the shop. I should be able to make this work. The manufacturer of the machine has the low down on the necessary phase converter to make it work. But, i'm glad to hear you thought the idler was not costing you too much.

1. 
   BigK | Mar 10, 2006 08:03pm | #4

   Kelvin,
   I'm not an electrician, just a carpenter/furniture/cabinet builder. Did a remodel for a commercial bakery a few years ago. We brought in 3-phase for his equipment. The sparky had to set 3 panels; 208/3-ph, 208/1-ph, and 110/1-ph as I recall. Compared to a 1-phase setup was rather pricey. When I got to build my shop a short time later the sparky wanted to do the same for me. After comparing the $$s of 3-ph vs. bringing 1-ph up 1 more pole and using that in my shop(200amp), the single phase was quite a bit cheaper.
   I would bet anything that if you brought 3-ph to your shop the power monoply would bill you commercial rates. Ouch!

2. 
   tinkerer2 | Mar 11, 2006 07:09am | #6

        Don't be to confident on that 100 amp service.  Again, I'm not an electrician, but if you are using some thirty horsepower -- Just a guess of roughly 7 amps per HP.  One hundred devided by seven equals about 14 HP.  I could be way off base but you might need over 200 amps for the motors and that doesn't include lights, heat, etc.  You might want to be very sure of your power requirements before you invest too much on this project.  Let an electrician look at it.  Incidently, I recently had my place rewired, 200 amps to the house and 200 to the shop.  I don't have nearly the amp requirements that it sounds like you have.

   Edited 3/10/2006 11:15 pm ET by tinkerer2

1. 
   kelvinpot | Mar 12, 2006 01:54am | #7

   Thanks guys. I've seen that they do make 7 hp single phase, but you hardly ever come across them. Wonder why? Boy, you are right! THose amps add up, especially if i add a rotary phase converter. Hmmmm. Maybe a genset? Hate to fork over $4,500 for the line. I've heard that the 3 phase definitely outperforms the single, and when you are spending over $10k (both machines are the same price, single or 3 phase) you want to make the right decision. I'm not exactly sure what "much better" means either. 10% better? 75%? I guess i should talk with some folks who run these things.

1. 
   tinkerer2 | Mar 12, 2006 05:18am | #8

      Seems like if you were in production and and the income justified the expense that three phase would be the way to go, especially if it was available just across the street.  I worked as a security guard in a factory that made faucets.  We had three 150 HP air compressors and six huge furnaces that must have drawn a huge amount of power.  Three phase is almost limitless.

3. 
   K1500 | Mar 10, 2006 10:17pm | #5

   FWIW, I am not anywhere near an electrician, nor have I ever run 3 phase.  I think the bottom line is how much of an improvement do you see in 3 phase?  If you were going to convert for a shop full of equipment, then maybe but it seems to be overkill for one machine to me. 

   Does the 5hp version just stink or do you want the 7hp version because 'it's better'?  I have fallen victim of the "Tim Taylor More Power" bug before.  While I cannot complain about more power, I have made some power compromises before that I didn't want to but in hindsight were smart moves.  I have also powered up and realized that I didn't need all the power and had spent money on something not needed.

   You know your needs better than anyone (and I don't have any idea how much 'better' a 3 phase 7hp is than a 1 phase 5 hp), but I suspect it will be a lot of trouble and expense to move up to a machine that will probably give you precious little 'real world' benefit.  Of course, if you are using the machine for 6+ hours a day, 5 days a week to make a living, then it may be worth it.

4. 
   dukeone | Mar 12, 2006 06:07am | #9

   Kelvin: I am an electrician (retired). Three phase power is not "superior" to single phase: a one HP motor is just that; one HP. There are other issues such as starting, reversibility, complexity and cost of motors and controls. The three phase power across the street from you may be at distribution voltage (2.4 to 12 kV) so the utility may have to mount a transformer to give you three phase at utilization voltage (208 to 480 volts) and if you have ever done it or watched the process you'll know why it is pricey. All that said if you can justify the cost go for it, maybe a separate service just for the shop @ 480 volts three phase. Once you get over the initial cost it will be the best arrangement; most industrial shops use 480/3/60 for the majority of their machines till you get above 300-500 HP, then you would want 2400 or 4160 volts (don't try that at home!!!). While were at it if you get 480 be very careful or hire an experienced electrician to wire your machines; 480 is known to be, in some ways, more dangerous then higher voltages due to it freezing your muscles to it rather then blowing you away from any accidental contact. Good luck, Duke

   Kenneth Duke Masters
   The Bill of Rights
   December 15 1791
   NRA Endowment Member
   LEAA Life Member
   CRPA Member
1. 
   kelvinpot | Mar 12, 2006 09:33pm | #10

   thanks guys for the input. Good ideas!
   Kelvin

1. 
   uhrich | Mar 13, 2006 01:53am | #11

   We run everything over 3hp (and most machines under) on 3phase power. We are a commercial shop in an industrial zoned area.In the long run, 3phase is great. Durable motors, low amperage draw, higher HP's, heavy-duty all the way.Short-term though, it is pricey. After all the main power supplies in a shop, you have to buy 3phase circuit panels, breakers, romex, fixtures and plugs. Just an estimate, a 30amp 3phase breaker costs ~$100! Everything 3phase is heavy-duty, industrial grade. If you're running a commercial shop, it's worth having, if not, stick with single phase.By the way, depending on your service provider, watch out for the so-called "WILD LEG." Some utility companies supply 3phase with two 120v and one 180v leg of power. If you are using equipment with transformers or electronic motor starters, do NOT run the 180v (Wild Leg) through them. It MUST go straight to the motor, or else you will fry everything! Also, people like to run auxilary 120v outlet(s) on a 3phase circuit. No Wild Leg here either! We always code the Wild Leg, using the red wire. It's not too important as long as you're consistent and check everything with a multimeter.Sorry about the long post...

1. 
   BarryO | Mar 17, 2006 10:56am | #14

   We always code the Wild Leg, using the red wire.

   Doesn't the NEC say you're supposed to use orange?

5. 
   mudman | Mar 16, 2006 05:20pm | #12

   Three phase is a better way to power motors, if you have three phase service. Three phase motors run a little better and are more reliable. They have fewer parts inside to go wrong (ie. starting circuit, capacitors). They are easily reversed (great for shapers). They run cooler for the same HP/voltage ratings because the amperage in the windings is reduced be 30%. They have more torque and their power is still availible as the motor begins to stall, a single phase motor's power drops dramatically as it slows down. They are relatively easy to control the speed (great for lathes) and there is no loss of power as you slow the motor. If you are using very big motors, 7 HP or more, the wireing gets aun manageable for a single phase 220 volt supply. Imagine the wireing needs for a 25 HP wide belt sander running 220 single phase!

   The down sides are that the resale on these machines is low, especially for home shop sized machines, Of course that means you can also buy them cheap, and some replacement parts are expensive (starter switches, breakers, plugs).

   Most all of the advantages of three phase motors are negated if you have to use a phase converter. The only exception for me has been price. I have been able to buy a monster RAS, air compressor, and lathe for dirt cheep. I use static converters on all of them so I always have instant on power. If you follow the manufacturers recomendations static phase converters work great and are affordable (less than $200 for a 5 HP unit). I may build a rotary phase converter some day using the static convertors I have, but I dont like the idea of having to start up the converter every time I need to use the tool/s powered buy it.

   Mike

6. 
   mudman | Mar 16, 2006 05:39pm | #13

    To add to my previous post, I reciently moved into a comercial warehouse and three phase rates are the same per KWHr as single phase in my area. However installing the transformer, running quad entrance line (20 feet), and changing the mast was going to cost $2,000. A three phase panel, disconnect switch, and breakers was over $800, and that was all used stuff off EBAY. The new disconnect alone was $900 new.

   Mike

7. 
   2x4 | Mar 18, 2006 12:39am | #15

   Kelvin.. I just had a 3 ph  rotary phase converter installed in my shop. It was a Gen-tec 20 hp converter and it cost me about $1100 usd. I bought it about 1 yr ago but just got around to having it installed last weekend. I bought all used electrical boxes and it included 3 disconnect boxes( FPE 30 amp), 1 distribution box ,all  this cost me $260. I bought a used 30 kva 3 ph transformer to go from 240 to 575 volts as this is what I require(Live in Canada). The transformer used was $450 CDN and it will cost me about $200 for the electrician. I run this with a 60 amp breaker from my main panel. There is a  shop down the road from me that runs a 9 head older Wadkin Moulder with a 100 hp rotary phase converter. This 100 hp phase converter runs off a 200 amp panel coming into his shop. There seems to be a lot of misconception about phase converters. My electrician works solely in the industrial area and he was very skeptical about how they would work. It was only after he personally talked to Gen Tec did he agree to hook it up . I needed 3 ph for an SCM slider and the guy I bought it from checked with his electrician and his electrician said phase converters do not work. I thank Gen Tec for their great aftermarket service. I would check with them for a price and mention that you seen their add on Wood Web. They have great prices and use Leeson generator motors.

   I must add upon the completion of the install my electrican checked the voltage on all three legs and they all were within 2 volts of 575 volts. Good luck

   Brian