Converting 3 phase, to single phase

[Phil Landwer]

I've got a chance, to buy a Powermatic 66 table saw, with stock feeder, at a rediculously low price.
Problem is, it's got a 3hp, 3phase motor on it. The stock feeder is 3 phase also.
I've only got single phase in my shop.

Do I pass on this then, or is there some way to convert this stuff to single phase?
What are my options here?

[Rod Sheridan]

Hi Phil, if it was me I would purchase a single phase motor for the saw and purchase a VFD (Variable Frequency Drive) for the feeder.

Optionally I would purchase a VFD for the saw and feeder ( 3 HP single phase to 3 phase units are innexpensive), as are the 1/2 or 1 HP units you would need for the feeder.

Regards, Rod.

[Matt Cook]

As previously mentioned, you can change the motor on the saw but it will have a cost associated to the conversion. The up side is you'll have a new motor on your saw.

I'll bet it's cost prohibitive to convert the feeder. That being the case, I'd start looking at rotary converters (I have one for two of my machines) to handle the supply for both. They're durable and can run for years. The up side is they're extremely simple and don't have complex electronics that can fail like a VFD or a static phase converter. The downside is they aren't cheap, they add noise to your work environment, and it has to be installed somewhere. I just looked locally and there are several for sale between $150 and $400 on CraigsList. You'd be hard pressed to get a replacement motor for the saw for that cheap.

I think the best decision truly depends on the sale amount of the machines and what it's going to cost to put them into service. In my experience, I've found that I can typically hold out for a more expensive, single phase unit, and spend less in the long run and end up just as happy. It can be hard to turn down a deal when someone looks at you and says "I'll give you both for $XX. I've been there many times.

More times than not, the 3 phase machines sell for less because of challenges most will have just wiring them up. Once you have a phase converter though, a whole new world of options opens up to you when shopping around for deals. If you do go the phase converter route, just make sure you get the right one for your application and understand the correct way to hook them up. Simple mistakes wiring a VFD or static unit could result in failure.

[Dan Friedrichs]

I think Matt overstates the likelihood of a modern VFD failing. Rotary phase converters are very old technology, and have many disadvantages.

You could buy the saw as-is, and connect it to a VFD (like this one: http://www.factorymation.com/s.nl/it.A/id.198/.f?sc=2&category=32) and be all set. At $185, that VFD is almost certainly cheaper than trying to convert either the motor or the feeder to single phase.

[David Kumm]

Phil, If you go the vfd route just remember you can't have a switch between the motor and the vfd so you need to wire directly and bypass the existing controls. If the saw has a manual switch you could choose to leave it on and just plug the vfd into the cord but a magnetic switch must be bypassed. Not hard but a consideration. The feeder will have a drum switch so although a vfd will work you won't be able to use the switch either. If you want to go the RPC route which opens up a whole wonderful world of machine choices,you avoid those problems. There is up front cost but it is worth it. But then I'm a guy with a RPC, a Phase Perfect, and a dozen vfds. That is how much I like 3 phase. Dave

[Thomas S Stockton]

the advantage of a rotary phase converter in this case is that he only needs one instead of vfd's which he would need to buy one for the saw and one for the feeder and then have to deal with re wiring the switches which may or may not be easy depending on how much knowledge Phil has about wiring.
When I needed 3 phase I talked to a company that sold both and they recommended a rotary which was really easy to set up and works well.
Tom

[Don Jarvie]

I found a 3hp single phase on the bay for 200. Its an AO Smith brand. Only issue is that it doesn't have an overload built in so I had to get a new magnetic starter which was another 60 bucks.

I looked at Rotary Phase converters and the one I would need would be around 500 to 600 so it was cheaper to swap out the motor and upgrade the starter.

A VFD would probably be cheap for the power feeder since its probably around 1hp. The VFDs for 1hp are pretty reasonable.

You'll like the PM 66. Mine is almost done and it looks great, very heavy duty.

Don

[Stephen Cherry]

I vote for the vfd just because you can use it to stop the blade when you turn off the saw. If you don't need the feeder, that would be a highly sellable item, depending on exactly what it is.

[Dave Cav]

I'm running five stationary 3 phase tools on VFDs, including a 2 HP PM 65 and a 5 HP Delta 12/14 table saw. Very happy with them (the saws and the VFDs). I agree that a power feeder is not very necessary on a table saw in a hobby shop. If you were a cabinet shop doing a ton of ripping, then maybe, but not at home. However, if you have a cabinet shaper like a Delta HD or a PM 26/27 then it would be very useful.

[Rick Fisher]

A VFD would service that saw just fine.. Another member here actually wired his factory switch on his jointer to operate his VFD and hid the VFD inside the jointer.. it operates like normal.

[Scott T Smith]

Phil, I have a slightly different take on your question.

If you don't anticipate buying any more 3 phase equipment, then by all means go the VFD route.

However, if you think that you may acquire more 3-phase equipment in the future, I would suggest that you look into installing a phase converter and feeding a 3-phase load center with it. That way you make the expenditure one time, and can keep adding 3-phase equipment in the future w/o having to keep purchasing additional VFD's.

[Chris Parks]

Having to switch the VFD is a bit of a pain but most VFD's can utilise a remote low voltage switch which can be placed on the machine or on a pull cord switch above the machine. In fact, for say a dust extractor, the remote operation can be done by switches at each machine.

[Jeff Monson]

I use a Kay RPC for my 3 phase needs. It was super easy to install and I have a X10 remote system on it. I can run most any 3 phase machine that comes along. I would not hesitate at all to go this route again.

[Jerome Stanek]

With a rotory phase convertor you can always add equipment that is 3 phase without buying more VFD's. You will find that used 3 phase epuipment is cheaper to buy and you will get more bang for your buck.

[Peter Quinn]

Phil, I have a slightly different take on your question.

If you don't anticipate buying any more 3 phase equipment, then by all means go the VFD route.

However, if you think that you may acquire more 3-phase equipment in the future, I would suggest that you look into installing a phase converter and feeding a 3-phase load center with it. That way you make the expenditure one time, and can keep adding 3-phase equipment in the future w/o having to keep purchasing additional VFD's.

Ditto from me. I put in a slightly over sized RPC, its an American Rotary from gentec, easy to install, works great. Now adding more 3PH equipment is simple and cost effective in most cases. I can run one or two machines at a time, easily can run a 5HP shaper plus power feeder plus another tool if started in sequence for instance. If you need the speed control that a VFD offers, or the breaking option, it may make sense, A lathe for iseems like a prefect place for a VFD. But on a cabinet saw? Could go either way depending on price and your needs.

[Phil Landwer]

What's the advantage to having 3 phase power in my shop? If any.....

[Rick Fisher]

Phil..

I have a dedicated 3 phase system.. it draws 100 amps of 220V PH1 and sends about 60 amps of 220V PH3 to a Siemens 3 phase panel.

The advantage is great if you a guy who buys used machinery ..

Today I paid for a used Felder FS900FK Edge sander .. its used and comes with a Felder 3 wheel PH3 1hp Power feeder. I will take deliver in another week or so ..

This machine is 4hp x PH3 .. and the Feeder is 1hp PH-3.. To run it off a VFD would be a pricey VFD..

To install it, I simply get 20 feet of #14 Tec cable and a Siemens 15 amp x 3PH Breaker. Snap in the breaker and run a wire.. I am good to go ..

The advantage is that used 3 phase machinery is usually much cheaper than used single phase machinery, when compared to the new price. The reason is that most hobby guys simply pass on it .. its too complicated, too much of a hassle.. Today, I can buy anything up to about 20hp .. Snap in a breaker and its running..

The sander I bought is about 5 years old and has been for sale for over a year.. it started at 60% of retail and sold today for 30% of retail.. Had it been single phase, it would have gone for much more.

The other advantage is that a lot of the really good machinery is simply not available in Single phase.. This sander is a great example..

VFD's are great technology but for example, my 3 phase x 4hp jointer cannot run on a VFD .. The motor has an aggressive electromagnetic brake that send the energy when breaking back to the power source, that burst of energy would either trip the overload on the VFD, but probably destroy it .. Electromagnetic braking is very common on higher end European motors. CEG has an entire line of them and many Euro countries factory safety rules include tools having brakes

The solution is to disable the brake on the motors, VFD manufactures can supply you with a braking resistor which will actually brake the motor, but its not in the league of an aggressive CEG brake. My jointer stops spinning in what seems like 2 seconds.. could be less.

3 Phase motors are great.. Smoother and quieter than single phase.. no capacitors .. My bandsaw is 5hp single phase, its a beast.. when I shut down the power, the energy dump from the run cap impressively loud.. 3 phase motors have none of that.. they are quieter, simpler and more reliable..

When I enter the shop, I turn on the 3 phase power.. The 3 phase machines are all hot and ready to run .. I have a wide belt with a 12hp motor and can run it while the 3 phase jointer is being used. The same will be true of the edge sander.. I could probably have all three running at once, but am not sure yet..

Setting up a 3 phase system is a bit expensive, but you only do it once.. after its done, you are completely liberated.. its like having it at the pole.. You turn it on when you enter the shop, and turn it off when you leave.

[Phil Landwer]

Well, it looks like I'm leaning towards getting a 5hp Saw Stop tablesaw instead. I'm hoping to steal it at about $1,000. It's in excellent condition, however it is 3 phase. What's the cost of a dedicated 3 phase panel. It looks like individual 3 phase controllers are about $185....but how much for a dedicated panel in my shop?

[Dan Friedrichs]

....but how much for a dedicated panel in my shop?

A panel simply refers to a separate breaker box for your 3 phase equipment, and probably runs $100-200 for a basic box, plus around $40 each for breakers. But unless you have 3phase available from the power company, you'll also need a rotary phase converter to generate 3phase from your existing single phase supply. On the low-end, Grizzly sells a 15HP converter for $2k. Like I said earlier in the thread, RPC's are very old technology, though, so you may be able to buy a used one cheaper.

Ultimately, unless you really envision a lot of 3phase equipment in your future, it will be cheaper to replace the 3ph motor with a 1ph motor.

[Brian Ross]

Cost of install has a lot of variables but I had a 20 hp rotary phase converter installed and the cost ws about $425 and that included a small panel that was used. My shop is quite open and it took about 4 hrs for the install. The electrician was a licensed electrician and charged me $45 an hr which is a real good price in my area. It is not uncommon to pay $90 to a larger company. I run 2 Rotary phase converters in my shop . Someone mentioned that they do not work well as it is old technology. My first one has been running flawlessly for 8 years. I got the second one as I bought a widebelt sander and it has a 20 hp motor and I wanted to lighten the load on the first one as it is only a 20 hp. I am a big fan of RPC's and American Rotary.

Brian

[Dan Friedrichs]

Someone mentioned that they do not work well as it is old technology.

To clarify, Brian, I think RPCs work fine, but yes, they are old technology - in the same way that carburetors can work fine, but are not the newest thing available. RPCs work by converting single-phase electrical energy into mechanical energy, then converting the mechanical energy back into electrical energy (but 3-phase, this time). This is an awfully roundabout way of achieving conversion. RPCs make noise, they are large, they have moving parts that wear, etc, etc. VFDs or static phase converters offer the ability to directly convert between single phase and 3-phase, without the intermediate mechanical step.

[Stephen Cherry]

To clarify, Brian, I think RPCs work fine, but yes, they are old technology - in the same way that carburetors can work fine, but are not the newest thing available. RPCs work by converting single-phase electrical energy into mechanical energy, then converting the mechanical energy back into electrical energy (but 3-phase, this time). This is an awfully roundabout way of achieving conversion. RPCs make noise, they are large, they have moving parts that wear, etc, etc. VFDs or static phase converters offer the ability to directly convert between single phase and 3-phase, without the intermediate mechanical step.

Vfd's don't really convert directly, they rectify, filter, and put out the juice to simulate 3 phase ac. And they do break, and they do have a limited lifespan. Although they probably would last a long time in a light duty shop, the chances of the average woodworker fixing one are pretty slim. For 3 hp, I think the balance tips to the vfd, and at 5, I would go with the rotary converter.

And how would this relate specifically to the sawstop? That's a good question, and I wouldn't want to try integrating the vfd into the sawstop. For the rotary phase converter, you would want to contact sawstop for specific advice on how to hook it up.

[Dan Friedrichs]

And they do break, and they do have a limited lifespan.

This is not exactly true. While any electronic devices are subject to some highly-unlikely unexpected failure, a modern VFD should not be "expected" to fail (certainly not compared to a RPC, which has moving, wearing, parts!).

I don't think the Sawstop merits any particular concern about VFD vs. RPC. The electronics in the SS certainly rectify and filter whatever input they are provided, so any minor difference between the power generated by these two options is inconsequential.

[David Kumm]

If the saw is the only machine to use 3 phase you can find a used vfd- probably 10 hp to handle the single in three out needs for about $350-450. Maybe less if you get lucky. New gets higher. If you continue with 3 phase equipment the vfd thing gets pretty cumbersome. While each machine doesn't need its own, from a practical standpoint that is generally what works the best. The RPC is a one time expense. You can get it done for $1000-1500 including the panel, starter, or disconnects depending on your configuration. If you want to go all the way, take a look at the Phase Perfect which is a newer technology converter that doesn't need a separate motor and manufactures balanced power. They don't come up often used and cost about 3K new and about half used. Dave

[Stephen Cherry]

I don't think the Sawstop merits any particular concern about VFD vs. RPC. The electronics in the SS certainly rectify and filter whatever input they are provided, so any minor difference between the power generated by these two options is inconsequential.

Um, this sort of assertion is a little scary. The sawstop contactor and switchbox (the thing that turns it on and off and runs the brake) are fully integrated- and vfd's can't have a contactor. My impression is that it would take an engineering effort to integrate a vfd into the sawstop, and then to validate the effectiveness of the safety device. Personally, I can say that I am pretty handy with motors, drives, controls, etc, but I would not take on that task with a 10 foot pole.

[Dan Friedrichs]

Ah, ok - you're right. I was thinking of power quality, not the contactor. Good point.

[Aleks Hunter]

I'd spend the extra $$$ on a much larger Rotary phase converter, you get good bang for your buck , 15 HP baldor units are USA made a and a little over a grand. The wire itself will likely set you back $50-100. Rotary converters to power a 3 hp saw and a 1 hp feeder will need to be more than 4 hp. When you saw into some thick hardwood for example, that saw motor will draw more than 10 amps that would be drawn by a three horsepower load. There is a big difference between the rating conventions for 220 volt induction motors than say shop vac universal motors which are often labeled with mathematically impossible horsepower figures.shutting the "sized to just fit" converter down. The bigger unit will be money in the bank, when you start wanting things like bigger jointers or planers that often come with with 7.5 hp three phase motors, you won't have to buy another converter. There is a reason three phase is so popular in industrial settings. You can use less expensive wire because the amperage coming over three wires instead of two, and depending on hwere you live, three phase may be a better way all around to go. Check with your electric company if you have a demand meter. The lower draw can mane three phase installation if available very cost effective. We have a demand meter and the threshold is 5kw for fifteen minutes. That's a planer and dust collector alone. not to mention "luxuries" like lights, water pump, AC in the summer, furnace pumps in the winter, you know, the frills! One last consideration when you put in anything with a large motor is power factor consideration. Depending on how single phase motors are wired and whit what capacitance, they can be several out of phase and power factor becomes a definite cost consideration. When things are out of phase with each other electrically you can draw up to 40% more Volt amps than the equivalent work you are doing. If your Electric bills seem high it is something to look at.

[David Kumm]

Aleks, it is worth mentioning that converter companies rate their units differently. There are different classes of starting load ratings. Most use the easy start rating so a 15 hp RPC is good for a hard starting 7.5 hp machine. A few companies-Kay is one- rate at a hard start so a 7.5 hp unit will start a 7.5 hard start machine. If you buy used you need to study the specific literature for the unit you are buying. If new talk to the company and take their advice. The new euro machines over 5 hp generally have a soft start feature mandated so they are easy or medium start while the old cast iron machines start harder, depending on the type of machine. You can add additional RPC units at a later date but not real cost effective. The newer units have some ability to be balanced a little better over a range of loads depending on the type. Dave

[Alan Schaffter]

I'd like to add to what Stephen said. SawStop has some delicate sensing circuits. I would first check the specs on any RPC then check with SawStop. Unless you do, you don't know what effect variations in frequency or voltage coming from an RPC (if any) might have on a SawStop. Better safe than sorry. This info isn't on their website so it may not be an issue at all, but it is definitely worth a call.

[Aleks Hunter]

I absolutely agree.
Get all of the information you can before jumping into all of this. For power supplying it is always better to have too much capacity than too little and having to go out and buy bigger anyway when you burn the little ones out. And the Baldor units have the nice bonus quality of being made in USA. We really do have to start supporting USA manufacturers. Before the country forgets how to mass produce anything.