Bought a great bandsaw at an industrial auction. Thought it was 220. (hey – it was dark !) Turns out it’s a “close to new” 3 phase motor instead.
Any suggestions as to whether I would be best to figure out a way to install a 3 phase circuit in my shop – or change the motor ?
(Please don’t suggest trading in the saw: At about 400 lbs it is not leaving the shop. Ever.)
Gavin Pitchford
“Sail fast – live slow” (build even slower)
Edited 11/8/2006 4:00 pm ET by Accelar
Replies
Change the motor out or buy a phase convertor. Either way it's a little more $$. If you are always looking for deals on equipment take a look at the phase convertor. Rotary phase convertors are a good buy, esp. at home wher you can plug things in one at a time when you use them.
You can purchase a converter that runs off single phase, and has a 3 phase output. An old friend of mine was an auction junky, had a pile of 3 phase tools, and he had a converter.
But if you don't plan on starting a collection, I would guess you best replace the motor.
H
Hmmm... I like the option of buying more $4000 3 phase tools at auction for less than $500. ;-) and as pointed out, seldom use more than one at a time, so converter likely the way I will go, but know nothing about them.
Any thoughts on a preferred manufacturer of a converter - or what the cost might be ?
And do they plug into 110 ? 220 ? or require a separate circuit ?
Thanks Gavin Pitchford
"Sail fast - live slow" (build even slower)
Ronk is a premier brand, there are others too. You want a convertor 2-3 Hp larger than your expected max load to cover startup draw. 5 Hp saw needs a 7.5 Hp convertor etc.Check ebay, used always sell cheap locally bc shipping is a killer. Check out http://www.owwm.com for more info.
Good luck.
I have a phase converter in my shop to run a 5-hp planer and a 2-hp table saw. There are three main options:
1. A static converter will run one machine at about 50% of it's rated output. So you might get 1-1/2 hp out of a three-phase motor, and you will also lose some torque. Cost will be a couple hundred bucks.
2. A variable-frequency INverter (or VFD) is a good option if you need to vary the speed of the motor. VFD's are commonly attached to lathes, although a bandsaw might be a good use for one. Not particularly cheap, especially at larger HP ratings. Possibly $400 to $1500 depending on size.
3. A rotary converter is great if you want to hook it up to a 3-phase breaker panel and run multiple machines. You will need a converter rated at 1.5 times the HP rating of your largest motor (MINIMUM). I highly recommend having a qualified electrician hook up any of these.
I have a 10-HP rotary converter made by American Rotary Converter. Cost, including the electrician's time and some additional parts, was about $1000. This is a brand new converter with a custom-made Baldor motor and a bank of run capacitors. You can do it a lot cheaper but you will have to cut some corners in doing so, either in size, quality or safety. I can START any motor up to 5 hp, and in some cases 7.5 hp, and RUN any motor up to 40 hp (yes, 40) without a starting requirement. It's run off of a 60-amp, 220v, single phase breaker in my main panel.
How many HP? WHat is the FLA of the motor? T rated speed? (this should be on the name plate)
If it is not too big (under 3hp, maybe under 5hp), Variable Frequency drives are getting pretty cheap. This would give you some soft start capability and you really don't have to worry about voltage spikes with 220V.
DOn't use the drive's ability to run the motor slow, just use it as a means to make 3 phase power and get up to speed.
REplacing the motor could be the easiest and cheapest option if it is not too big and a standard frame/mount/configuration. You can get single phase motors pretty cheap at Farm Supply type places.
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I have runn quite a bit of machinery off phase converters(rotary phase converters) and They work quite well. As I have it now, I have 220 single phase sub panel in my shop. In that panel is a 100amp breaker that supplies the 100amp power disconnect that goes to the 15 hp phase converter and another sub panel which is a 3 phase panel.
The cost of a converter like mine is aroud $1000-$1500.
The sigle phase subpanel and breakers is $60
the 100amp disconnect ran around $200+
The three phase panel is an old "Square D" and I think they run around $200, but not sure.
Probably around $50-$100 in misc #2 wire, conduit/electrical boxes, not including 3 phase plugs and recepticles
With this setup, I can run up to 45 Hp of collective motors, with no single one over 12-15 hp. The largeset single machine I run is a 10 hp 37"wide belt sander that has a smaller 1hp feed belt
Be careful if you plan to use a static converter. they don't work on compressors, powerfeeders or other motors that have constant high loads. These are usually sized for each individual machine by the hp rating of the particluar motor.
I use one of these when I need to take my line bore/hinge drilling machine to a job site. When I do, I have to be careful not to ever stress the machine. The rest of the time, it is only used with a rotary converter
As for power rating, My understanding is that a static will give you only 60%+/- of the motor rating and a rotary will give you 90%+/-
As for changing the motor, a 5hp three phase motor is about the same frame size as 3hp single phase motor. Magnetic starters/switches might have to be changed out also. Maybe not because most three phase controls are run on 220 single phase( two of the power legs. as in L1 and L2, or L1 and L3).
Be very careful that the manufactured leg doesn't supply the single phase controls for the machine
Someone correct me if I'm wrong... I know you will
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html
Build your own maybe? This sounds pretty complicated, but Junkhound can probably tell you how to cobble one up from an old blender and some feathers.
Joe H
My rotary's an old 3 phase motor, cost $5, switched from single phase and started with kick on the chain drive that came with it. Powered 36" bandsaw, Unisaw, 12" jointer, dual spindle shaper, and dust collector for the past 20 yrs with no problems.
Now that I have enough current available for my 24" planer and 42" sander, I'm looking for a large enough 3 phase motor for a phase converter for them. Needs to be 15 hp so need to pay attention at auctions.
Capacitors are better, but I never bothered.
The one static converter I owned made the newer motors run very hot.
No feathers. PAHS Designer/Builder- Bury it!
Have a extra 25 HP 3 phase motor you can have free - just pay shipping ... ha ha... old one, only weighs about 300 pounds.
Was thinking of using it for a counterweight on the back of a loader.
I'll take it - Just bring it no the plane with ya next time you come to Illinois.(-:
When asked why he doesn't support the Dems like most minorities do: "I decided I was tired of living on the liberals' plantation." [Walter Williams]
Boy, Boss is fast. I was gonna suggest something similar. Surely I have some stuff you'd like to play with. But 300 lbs? Might be better on a tractor. Had a guy offer me a 50hp one once. Didn't bother to drag it home. Great counterweight potential. Likely still sitting there if you want it.
I actually had a 15 hp rotary converter once. Homemade (not by me) that used a 120v motor to start it spinning. At the time I didn't need such a large one and couldn't see paying for all the kwh consumed with it spinning in the basement for 8-9 hrs/day. That's when I went with my present 5 hp one and saved considerably more than that $5 the first month.
When I had the opportunity, I also checked out a commercial rotary. Didn't want to fry it (and have to pay for it @ $600) so I used an induction ammeter and turned on 1 machine at a time until I had everything spinning. Total draw from the panel was 49 amps. Worked fine, even though it was only rated 3hp.
I've never understood exactly why they work, but other than losing efficiency and some power, no problem. Easily justified by low prices on used 3 phase tools.PAHS Designer/Builder- Bury it!
Joe --
You beat me to it on the three phase converter web site. Here's a whole bunch more good info on motors:
http://www.baldor.com/pdf/literature/PR2525.pdf
-- J.S.
The following is a repeat of the post I made in '04. I don't have time to check whether the links are still good, but hopefully there will be something out there...In case any of you want to make your own 3phase rotary converter from an old 3phase motor to run all that old 3phase planners and saws you bought in great shape for next to nothing, the following articles can give you some hints on how to build one while minimizing getting electrocuted:http://home.att.net/~waterfront-woods/Articles/phaseconverter.htmhttp://www.taunton.com/finewoodworking/pages/w00126.asphttp://www.team.net/www/shop-talk/hm3phase.htmlhttp://www.metalwebnews.com/howto/ph-conv/ph-conv.htmlhttp://www.metalwebnews.com/howto/phase-converter/phase-converter.html
The best solution is to have a VFD, or 'frequency drive', installed. While the price might scare you, it will also allow for "soft starts" and speed control. It will greatly help you get the max out of your saw.
Price won't scare me as much as the thought of playing with the blender and feathers again. Made a heck of a mess last time. Although the thought of paying more for the "receptacle" than the saw does scare me a bit. Not so much writing the check - as explaining the check...
I now need to confess my ignorance - Speed control ? Is anyone out there prepared to explain to a newbie what three phase is, how it provides speed control, and soft starts ?
Very grateful for all contributions thus far. Thank you.
Gavin Pitchford
"Sail fast - live slow" (build even slower)
It is not the "three phase" that provides the soft starts, and the speed control... it is the electronics in the frequency drive. Frequency drives are used quite a bit in industry. Their size depends on the size of the motor that they control. They take the incoming electric... in this case 240 volt single phase... and convert it to 208 volt three phase.
More importantly, they also regulate the frequency of the AC power. The power company provides electricity at 60 cycles per second. The frequency drive can be set to vary that... more cycles means a higher RPM for the motor, fewer cycles means a lower RPM.
The drives also "ramp up" the cycles when you start the motor. That is, for but an instant the power is at 10 cycles, then 20, then 30,... until the set RPM is reached. While this all takes place in a few seconds, the result is that the motor has a 'soft' start.
I built a converter for my shop years ago. I run 3hp lathes and milling machines. I bought a variable hp static converter, it will start any motor up to 10hp. I then start a 5hp motor that idles on the foor. The idle motor generates the 3rd leg. This makes a set-up like the more expensive rotor phase converter. Good startup torque and instant reverse.
The static converter only needs to be big enough to start you idle motor which is larger then the machine motor you run or my buy in future.
good luck Bruce
http://www.grainger.com/Grainger/wwg/productIndex.shtml?originalValue=motor+drive&L2=Adjustable+Speed&operator=prodIndexRefinementSearch&L1=Drives%2C
The above is a link to the grainger page for variable speed motor drives. You can feed them with single or 3 phase, as they convert to DC and then switch that into 3 phase 0 to 70 Hz. Great for speed control applications. I've bought one of the 3 HP versions of the telemanique devices and it works good (for the corp, wouldn't fork out my own $$ over $20 for any motor myself <G>)
You probably should go that route if you dont like blenders and feathers. Speaking of which, WA state ignoramusses just passed an 'initiative' that 15% or our power needs to be generated by feathers (props?) and blenders (darius turbines) by 2020 - bet that gets rescinded when power rates go up 50%.
If you want to try, maybe the first thing to do is just wrap a cord around the motor shaft, connect 1 phase to 240 Vac, and pull the cord briskly - the 3 phase motor will then continue to run nicely (at slightly less than 1/3 the rating) on single phase.
From there, you can dispense with fancy switching and capacitors for starting and hook up a small 1 phase motor to start your rotary phase converter.
Joe's link is a good one for run capacitor arrangements.
This place sells VFDs for pretty reasonable prices. http://web6.automationdirect.com/adc/Home/Home Click on AC drives (variable frequency.) There are several other similar companies with similar products out there. For a 1hp, 230vac single phase in / three phase out, they have one for $125. For 3hp, they sell one for $289.
Suggest you have a look at Home Shop Machinist http://www.homeshopmachinist.net and post in its companion forums (http://www.homeshopmachinist.net/bbs/). This magazine has had, over the years, a few d-i-y projects and some advertisers. Never had a need myself so am in no position to give any feedback.
Another possibility is Lindsay Technical Publications http://www.lindsaybks.com/. They have d-i-y books on "everything" - no exaggeration.
I am not connected in any way with these companies.
Cheers
Many thanks to all for the care and effort in posting links and advice. Looks like I have a lot of reading to do. And here I thought I was going to get a quick, easy consensus as to the best solution ;-)Gavin Pitchford
"Sail fast - live slow" (build even slower)