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3 Phase Motors

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Forum topic by John posted 05-30-2009 05:44 AM 2939 views 0 times favorited 26 replies Add to Favorites Watch
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John

219 posts in 2863 days


05-30-2009 05:44 AM

I am considering buying a older PM66 at a great price but has a 3 phase motor. The seller said he knows someone that can make me a converter if I have a 220 outlet for it(which I do) but since i’m not familar with 3 phase motors, i’m not sure if it’s worth the trouble and if it work correctly. Any insight would be helpful and appreciated.

Thanks
John

-- John


26 replies so far

View Karson's profile

Karson

35035 posts in 3862 days


#1 posted 05-30-2009 05:53 AM

My table saw is three phase. I bought a static phase converter on e-bay. If the price is right on the saw go for it.

I’ve used phase converters for about 30 years on tools that I’ve owned.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware soon moving to Virginia karsonwm@gmail.com †

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RBWoodworker

432 posts in 2813 days


#2 posted 05-30-2009 06:44 AM

That’s true..you can buy a phase converter from Phase o-matic for about 160 bucks or so, but beware..the converter reduces the HP of your motor by about 1/3rd if I’m not mistaken..correct me if i’m wrong..but other than spending thousands of dollars hiring an electrical firm to swap out your electrical panel..this is the way to go.. my PM66 has a 5hp single phase motor but I bought it that way..

-- Randall Child http://www.racfurniture.com/

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marcb

768 posts in 3135 days


#3 posted 05-30-2009 07:49 AM

3 letters, VFD for 3 HP or less its the cats pajamas. For 5 HP or more its expensive as all heck.

I would say skip the static phase converter and go for a VFD, the next stup of is an RPC which can power multiple machines.

I run a VFD on my table saw and it works like a NEMA magnetic starter, brake and several other features all in one little box.

View Kent Shepherd's profile

Kent Shepherd

2716 posts in 2747 days


#4 posted 05-30-2009 04:30 PM

I love three phase equipment, but it’s not for a small shop. I get great deals at auctions because nobody around here wants it. I just ordered a single phase motor for a Powermatic for a customer to replace his
3 Phase. The motor, with switch and tax was just under $600. I’ve not used phase converters, so I can’t say how well they work, but it might be a valid option. Good luck.

-- http://shepherdtoolandsupply.com/

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John

219 posts in 2863 days


#5 posted 05-30-2009 04:41 PM

Well, the PM66 is only 2 HP but I was thinking that I could easily swap it out with a 3-5 HP down the road. I’ve been using a 1 1/2 HP contractor saw for so many years, even if the phase converter drops it a hair, I may not even notice it. Right??!? I don’t know, maybe wishfull thinking. Here is a link to the saw, and thanks for the info so far.

John

http://cgi.ebay.com/POWERMATIC-MDL-66-TABLE-SAW-2-HP-10-LEFT-TILTING_W0QQitemZ270399053446QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3ef50a1e86&_trksid=p4011.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

-- John

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marcb

768 posts in 3135 days


#6 posted 05-30-2009 04:51 PM

3 Phase has far more torque than a standard induction motor. My 2 HP 3 Phase table saw chews through wood as fast as I can push it through. I’ve ripped max capacity on it (10” saw, just a bit over 2.5 inches) and just pushed the wood as hard as I could through the entire cut.

5 HP is way too much for a 10” saw, you’ll reach the capacity of the blade before you reach anywhere near 5 HP. 3 HP is in reality probably more than you’ll ever use except maybe that .01% of cuts that may tap into the potential.

I would guess that the 2 HP VFD from here: http://www.factorymation.com would be what you need. cost is 145 for the vfd, you can also buy buttons and stuff from there to get a nice big red stop button and start button setup that you mount to the fence rail or wherever. I’ll try to get a pic of what I have as an example. Total cost with buttons would probably be about 180ish

I say go for it, looks like a nice saw, and 3 phase really kicks butt with its extremely smooth running power.

View RBWoodworker's profile

RBWoodworker

432 posts in 2813 days


#7 posted 05-30-2009 05:02 PM

Now I’m starting to feel dumb.. not sure what all the abbreviations are from the other fella’s ..lol anyone care to break down just what VFD is?..lol also as far as the 5 hp goes..I have used everything from the 1/4 hp to 10 hp and for what i do.. (Cut stock that’s 3” thick) I need all the power I can get..I guess that’s why I bought the 5..but that’s just because I needed to extra muscle, but beware..that motor on my powermatic 66 cost over 900 bucks if it ever goes out..yikes!!!!

-- Randall Child http://www.racfurniture.com/

View John 's profile

John

219 posts in 2863 days


#8 posted 05-30-2009 05:30 PM

Yeah, I’ve worked for 3 different Cabinet Shops and 1 Wood Working Shop and only 1 had a Table Saw (PM66) set up with a 5 HP motor. The only thing the saw was used for was milling. We had 1 other Table Saw (PM66) 3 HP and a 5 HP Sliding Table Saw for the Cabinets. I’m sure the 2 HP will be plenty and when it goes bad, i’ll swap it out with a 3 HP. This really helped and hopefully one day my experience will help someone else.

Thanks Again
John

-- John

View marcb's profile

marcb

768 posts in 3135 days


#9 posted 05-30-2009 05:54 PM

3 phase motors don’t really go bad, you might have to swap the bearings but that’s it (so a 20 buck fix)

A VFD is a magic box (don’t laugh that is the best way to think of it).

You supply it with single phase power, it then does magic and you have true 3 phase power coming out of it.

It also has some really useful features. It acts similar to a NEMA starter giving protection to the motor from too much power being drawn. Many also have a power break feature that dumps power through an external resistor for quick stopping (great on a bandsaw, works fine on a tablesaw don’t let anyone tell you different). Most can detect if the motor is slowing and give it a torque boost making powering through those tough grain areas a breeze.

My VFD also somehow managed to detect the 2 kickbacks I’ve had and shut the machine down thus really slowing the piece down (not that I was any where near the piece, but its nice that my door wasn’t destroyed)

VFD’s also have variable frequency output (Variable Frequency Drive is what it stands for). Induction motor speeds are based off of the frequency of the power (60 Hz in the US) Most go to 66Hz. Depending on the style of circuitry used you might have a low torque issue on the low end of the spectrum.

The frequency part is good for Drill Presses and Lathes and what not, but not really a feature that needs a lot of going into for a Tablesaw or most other equipment.

Its the best solution to a single machine need for 3 phase power. After that you need to look into RPC’s which depending on the size can power an entire shop or a couple machines at once.

Some shops that use an RPC for 3 phase power also have a VFD on the most frequently used machine (RPC’s are at their most simple a Static Phase converter that use a stand alone 3 phase motor to generate the 3rd phase of power) this way they don’t have to run the RPC the entire time in the shop in case they want to use the saw.

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John

219 posts in 2863 days


#10 posted 05-30-2009 07:19 PM

See, that’s what I like about this site. Woodworking, it seems is the least of the knowledge here, even though I don’t understand everything being said. It’s good to see it broken down for someone like me. This VFD sounds like something I need to look into. Thanks Again.

John

-- John

View SCOTSMAN's profile

SCOTSMAN

5839 posts in 3046 days


#11 posted 05-30-2009 07:59 PM

I dont see why anyone would need variable speed on a saw like this but many other machines like lathes etc work great with it I have many machines I own a 3 phase static 7.5hp and a rotary 5.5 hp newly bough last year and a vfd 5.5hp for my milling machine.I need another vfd variable frequency drive which gives speed control the only one of these that does anyway if you get ioffered 3 phase don’t be put off having this supplied to your house might be cheaper than you thing think it over.There are a lot of good machines out there going for low money simply because they are 3 phase and all hobbiests or most of them are wary of this but it is the way to go in my humble opinion regards Alistair

-- excuse my typing as I have a form of parkinsons disease

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marcb

768 posts in 3135 days


#12 posted 05-30-2009 08:26 PM

I dont see why anyone would need variable speed on a saw like this

As I stated it is a feature that isn’t really something to worry about in a Tablesaw, all the other features that a VFD offer make it a prime candidate for a tablesaw however.

Static phase converters suck away power (its basically a kick in the butt to get the motor started then running it off single phase 220) and a RPC needs to be started and stopped when 3 phase is needed. Neither of which is ideal for 1 machine occasional use.

With a VFD you get over current protection, torque boost, and a starter with remote push button station capability, and if wanted power breaking. All for about 140 USD which is equal or less than the other options, especially if you need to put in a good magnetic starter on the machine.

View TopamaxSurvivor's profile

TopamaxSurvivor

17655 posts in 3137 days


#13 posted 05-30-2009 10:01 PM

The some one who is going to make you a converter will probably take a three phase motor and connect it to 220 single phase. Then connect the three phase equipment to to the previously mentioned motor. It will get your equipment running, but it’s not very efficient. If you can find an old three phase motor cheap, it will work. You have to remeber to give it a spin when you start it. It will not spin on it’s own. If you spin it the wrong way, yoiur equip will be going backwards. Stop and spin it the other direction :-))

If you use a VFD, you will have to over size it by at least 1/3 to run it on single phase input. Since they turn the juice to DC, then back to AC, it doesn’t really matter what the input is as long as it is the same voltage range. With the VFDs avialable today, I wouldn’t bother with a phase comverter.

If it were me, I’d just swap the motor for a single phase 2 hp and wire it 220 v.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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TopamaxSurvivor

17655 posts in 3137 days


#14 posted 05-30-2009 10:23 PM

Sorry to say, 3 phase motors do occasionally go bad just like anything else man made ;-(( There is very little to go wrong excpt the bearings if they are not over loaded or over lubed. If you check one with a high voltage mega ohm meter and get a reading of 10 k or under, the motor will eventually go bad. The mfrs will say 10 k is good, but in my experience over the last 40 yrs, it ain’t!! The meggar should read near infinity in most cases when checking motor insulation.

Another poiint to consider, modern VFDs on old motors will, in most cases, burn out the motor insulation. The older motors were desinged to be used at 60 cycles. Modern VFDs put out unlimited cycles of switching action to fool the motors into thinking they are running on 60 cycle 3 phase. This can also cause a lot of noise in electrical power systems if it isn’t properly filtered out.

When we change out installations to VFDs on various applications, we always change the motor to a rated motor these days. The older motor are not going to be able to handle the drive in most cases,, especially if the motor is more than 20 years old.

marcb, I have no doubt your VFD was able to detect a kickback and stop the motor if the parameters were set up tight enough. It could even go into barking mode if yoiu programmed it to.

That’s it in a nutshell for the novice reader. All you technical types, make a few corrects none of them understand ;-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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marcb

768 posts in 3135 days


#15 posted 05-30-2009 11:25 PM

If you use a VFD, you will have to over size it by at least 1/3 to run it on single phase input

That depends on how the mfg labels the VFD, I straight up ignore the HP rating and just look at the FLA amps. Match that up to your motor and you’re fine for single phase input vfd’s.

And the insulation thing depends on many things. I’ve seen plenty of people running old motors fine. Probably depends on exactly how old. Powermatic didn’t make the 66 until the 60’s. Pretty sure you’re fine on that end.

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