Phase converter

[Bruce Koch]

I purchased a powermatic Model 90 lathe three phase thinking I could just put a different motor and switch to make work in my single phase shop. I found out that the variable speed also needs power. It has a baldor 1.5 hp 3 phase motor on it so what do I need for a converter rotary or static? I'm using the lathe mainly for turning for fun. I have a 1.5 single phase for it. Thanks in advance. Bruce

[Ryan Hellmer]

A variable frequency drive is exactly what you need. Should be able to find one for this application for less than $200.

Ryan

[Rod Sheridan]

Bruce, I'm missing something here.

If you have a three phase lathe that's 220 or 240 volts, all you need to do to make it work on single phase is add a VFD. (Variable Frequency Drive)

If the lathe already has a VFD, check to see if it's OK for use with a single phase input, many small models are.

That way you wouldn't have to change anything.................Regards, Rod.

[Kirk Poore]

Get a VFD (variable frequency device). It will convert to 3 phase, and will let you change the frequency, thus allowing additional speed control. A 2 hp model should set you back less than $200. I have one on my Delta HD lathe and it works great.

Kirk

[michael veach]

I learned something new today. I have used VFDs but it was always 3ph in 3ph out I did not know that they could be used as a converter. Any day you learn something new is a good day.

[jim goddard]

Ive been looking into this and saying a VFD is the answer may be premature. As I understand it not all motors will run happily on a VFD.

[David Kumm]

The odds are that a motor won't like a RPC due to the voltage imbalance than a vfd. Many vfd problems with motors relate to the 440V systems rather than the lower voltage. Never say never but there are worse things to worry about. Almost all 3 phase input vfds work with single phase input. Some manuals spell it out, some don't. Check with tech support. Dave

[Ryan Hellmer]

It is my uneducated belief that the voltage imbalance with RPC's is of little consequence on low-voltage, low-power (less than 20HP) loads. Also, as for VFD's being hard on motors, from what I've read, the only real risk is trying to run a standard motor at very low/high frequency. Inverter duty motors have very wide tolerance for frequency/speed and are very well insulated to address additional heat that may not be dissipated at low speeds. I personally use the VFD mostly as a phase converter and only vary frequency slightly to fine tune speeds. A TEFC standard duty motor running at 25 hz likely won't be able to cool down and heat=bad. Don't push the envelope too hard and you should be OK.

Ryan

[Stephen Cherry]

Here's a great, but incomplete PM 90 project (no stripe):

http://www.sawmillcreek.org/showthread.php?159704-PM-90-restoration-complete!&

Mike went through each of the three phase options, and ended up with a very nice setup.

[Rick Fisher]

VFD's will work in most cases, the exception is when the motor has an electromagnetic brake. Those motors create electricity when braking and dump it back into the power supply, a VFD will either trip or more likely be damaged in that instance. On a lathe, its a great application because of the ability to slow down the motor, but as someone mentioned, the motor can overheat if its relying on its own fan for cooling.

Rotary converters will supply a balanced load until they are run over about 75% capacity.. As they reach their maximum amperage, the voltage on the third leg starts to drop. This is not really a big problem with most woodworking motors, but causes heat and technically shortens the life of the motor.

You can also get what is usually called a CNC Rotary which is designed to not overload and typically keeps the voltage within 7% of the other 2 legs.

Not all Rotaries are created, or labelled, equally.. you tend to get what you pay for.

[David Kumm]

Although pricey, the third alternative is the Phase Perfect electronic converter. No motor but similar to a vfd in that it produces all three legs and is balanced within 2%. I switched from a Kay RPC to it as I have machines from 1 to 10 hp and for the first time all machines are running at full strength on balanced power. I am a huge fan. If you run several machines it is worth a look. Dave

[Rick Fisher]

Although pricey, the third alternative is the Phase Perfect electronic converter. No motor but similar to a vfd in that it produces all three legs and is balanced within 2%. I switched from a Kay RPC to it as I have machines from 1 to 10 hp and for the first time all machines are running at full strength on balanced power. I am a huge fan. If you run several machines it is worth a look. Dave

Hey David. I have the Phase Perfect as well. lol.. I don't promote it because of the cost but its really the creme of the crop in my opinion..

[David Kumm]

Rick, I got lucky and found one that was used-unused- and still in the wrapping. My understanding is that they are a great US company with very good support for their products. I was told of a unit that fell off a truck and the company repaired it for a few hundred bucks. Good word of mouth. Dave

[jim mills]

So can you give us a ballpark figure at what these units cost?

[David Kumm]

Jim, go on ebay. The units are listed new under phase perfect and better explained on their website. The smallest unit runs 60-70 amps single phase in and 35 amps out on all three legs. Dave

[Rick Fisher]

They basically come in 10hp, 20hp and 30hp sizes.. I have not looked at the site lately.
They are made in the USA, if my memory serves, North Dakota or somewhere like that.

If you have a 10hp .. and need more power, you can run another 10hp in parallel and basically have a 20hp.. So while size is important, its not the end of the world.

The 10hp version is approx $3600.00 .. I got the 20hp model because it was only $1000 more.. I say that meaning that $1000 more is much cheaper than adding another 10hp model .. it was a lot of money.

You could literally drop one on a cart, put a 220V plug on a wire, and plug it in the wall... The machine is not fussy, If I plug mine into a 30 amp x 220V receptacle, it will produce about 16 - 17 amps of 220V PH 3 power.. If you rolled it over to a 50 amp.. it would probably produce about 27 amps of PH3 ..

The 20hp weighs about 100 lbs.. It has no motors other than 2 fans for cooling, and draws about 200 watts idling..

If you compare to a big rotary of similar capacity, it would probably weigh 450 lbs, and could easily draw 7 amps idling.. 7 amps x 220V = 1540 Watts.. At est.. 12 cents per KWH.. your looking at 20 cents an hour instead of maybe 2-1/2 cents an hour to idle.

End of the day, its pricey.. but not that much more than a really high quality, CNC balanced RPC capable of the same amperage. The 20hp will develop 64 amps of 220V PH 3 power..
Compare that to the TemCo AC-29.. It can produce 62 amps of continuous inductive load. Its $2700.00 and weighs over 700 lbs.

[jim mills]

Great info Rick. After reading this, the electronic converters seem like the way to go. Quiet too...

[David Kumm]

Jim, Similar to regular RPC units, the PP allows for multiple machines. I can run my 10hp shaper, powerfeeder, and have been told 5hp DC with the small unit. Haven't tried it but they are definitely stronger than the ratings. The small unit can be had for 2995 direct from the company. Shipping isn't bad as that unit weighs about 75 lbs. Dave

[Alan Muller]

VFD's of the usual sort work by rectifying and filtering the input power to DC. The output is synthesized from that DC bus. So most VFDs will work with input on two of the three legs. There might be some derating, but it won't unbalance the output....

If you are concerned about old insulation tolerating inverter spikes-a valid concern-you can get "reactors" (chokes) to put between the VFD output and the motor terminals.

The main thing to remember is that slowing the motor down is NOT equivalent to mechanical speed reduction. Gears or belts increase the torque as they reduce the speed. VFD doesn't.

am

[jim mills]

Dave, what I was told is that RPC's have a rating like "10-30" meaning it can start one 10 hp motor at a time and run up to 30hp continuously. Is the PP similar?


Jim, Similar to regular RPC units, the PP allows for multiple machines. I can run my 10hp shaper, powerfeeder, and have been told 5hp DC with the small unit. Haven't tried it but they are definitely stronger than the ratings. The small unit can be had for 2995 direct from the company. Shipping isn't bad as that unit weighs about 75 lbs. Dave

[jim mills]

ALan, I was given a sales pitch regarding a 3ph 5hp shaper recently: With the included VFD, you can slow the machine way down for sanding and speed it up way past 10,000rpm for using router bits. I was skeptical!


The main thing to remember is that slowing the motor down is NOT equivalent to mechanical speed reduction. Gears or belts increase the torque as they reduce the speed. VFD doesn't.

am

[David Kumm]

Jim, I don't know if the ratings on phase perfect work exactly the same. I can run my 7.5 hp planer with a 1.5 feed roller motor and my 5 hp jointer together but since I'm alone and have no friends I don't know what would happen if they were both under load. An RPC is creating the third leg but the machine is pulling the two utility legs and the RPC leg whereas the PP manufactures all three. Seems like that would restrict it a little. Not relevant for me as a loner. I left my Kay RPC installed and use a double throw disconnect so if one system goes I can switch over or if I just want the utility single phase I can do that as well. I do consider the PP to be one of my best tools. It doesn't take much imbalance to derate a motor but it was mainly the droning sound of the RPC that got to me. RPCs can be made pretty cheaply though if you have the motor. Dave

[Roy Turbett]

If I understand you correctly, you have both a 1.5 hp three phase and a 1.5 hp single phase motor. Either one will work. If the lathe was originally shipped with a three phase motor and you want to use the single phase motor, you can use the stock magnetic starter but will have to change out two of the three heaters because the three phase motor draws fewer amps. You only need to change two of the heaters because the single phase 220 only uses two legs and the third leg is abandoned. This is the configuration I used for my PM 90 and when I wired it I took the starter to an electric supply outlet where they matched the correct heater for the new motor. A wiring diagram and manual for your lathe is available at OWWM.com.

If you use the three phase motor you will need a VFD. I'm not familiar with how to wire one but many, if not most, turners prefer this setup because it allows you to use the Reeves drive in conjunction with the variable speed control which gives you a wider range of speeds while still taking advantage of the greater torque you get from a pulley system. For example, the standard PM 90 speed range is about 360 - 2100 RPM. A VFD will allow you to go from 0 to 2100. You may want to go slower than 360 when roughing out a bowl and faster than 2100 when finishing a pen. By putting a larger sheave on the motor you can increase the range on the Reeves Drive to say 500 - 3000 and use the VFD to go from 0 to 3000. Some VFD's also allow you to run the lathe in reverse which some turners prefer to do mostly while sanding.

[Mike Cruz]

Bruce, Steve Cherry is right about my project...no stripe...not complete! :)

Steve helped me (okay, he DID it) with my VFD. A VFD gives you all the options that you would want your PM90 to do, but it wasn't equipped with from the factory. I bought the TECO FM50. For a 1.5 hp motor, it is about $150 IIRC (actually, I think that one goes up to 2 hp). It works great. I ended up with putting a 2 hp motor on mine, but only because I put risers on it so it now has an 18" swing. If yours is still 12", 1.5 hp ought to be plenty.

Not sure that I fully understand why your variable speed needs power. I mean, it should operate on a reeves drive. But if the variable speed is electronic, I think I'd need more info to try to help out.

[Alan Muller]

ALan, I was given a sales pitch regarding a 3ph 5hp shaper recently: With the included VFD, you can slow the machine way down for sanding and speed it up way past 10,000rpm for using router bits. I was skeptical!

Jim:

I seen nothing wrong with designing a machine that way. VFD's offer all sorts of great possibilities. The key is "designed" (!). That the motor has been evaluated for adequate cooling and mechanical integrity under the full range of operation.

An example of where problems arise is putting a VFD on a lathe and taking long heavy roughing cuts on large diameter work at low speeds. Even if the torgue is there, the motor cooling won't be. Still, it may be a useful setup if the limitations are understood. I've seen DC drives with separate cooling blowers to maintain cooling at low speeds.

I have a VDF on a 10" radial arm saw. It's beautiful to use. can set the ramp up, braking, direction of rotation, speed, and torgue to suit. Runs smooth as glass. Two-button control buttons hook up directly. Overall, much nicer than a single-phase saw.

I also have a drill press with a DC motor and a powerstat. I like this setup too--it will stop if the drill catches, and no need to change belts except for heavy work. DC motors are around--in treadmills and washing machines, for example, and a reasonable alternative in many cases to induction motors and FVDs.

Alan

[Bruce Koch]

I have the wiring diagram and it shows a micro switch in the head. There is also a conduit going to the head. I'm thinking of going with a rotary converter and not change anything on the lathe.

[Mike Cruz]

If it is what I think it is, that is a fail safe that will not let the lathe turn on without being in the START position. I disconnected mine. The reason was pretty simple. What if you are turning at 800 rpm. You turn the lathe off. Now you want to start it up again. Well, you aren't supposed to move the variable speed control (reeves drive) while the motor isn't turning. So, the only way to get the handle back to start is to manually turn the spindle with the outboard disc while slowly turning the handel back to start. I understand why they do this for a "school" setting...you don't want some 17 year old turning the lathe on at 2000 rpm with an unbalanced 11" blank on there! But for me, a one man shop, that has no one but myself to blame for anything, I don't need it. Just disconnect it, and get a VFD. You'll be happy you did.