1 phase vs. 3 Phase

[Jonathan Szczepanski]

I was drooling over the Powermatic 66 this weekend at the Baltimore woodworking show. The saw comes with different horsepower motors, but it also comes with different phase motors, 1 phase and 3 phase.

3hp, 1 phase - $2300
5hp, 1 phase - $2430
5hp, 3 phase - $2300

Other then the cost, what is the difference between the 1 phase and the 3 phase? What is the benefit of one over the other?

[Jamie Buxton]

The cost is the primary difference. It is possible to build higher-HP motors for lower cost with 3-phase supply.

However, if your shop is in a residential neighborhood, your electric company is likely to provide only single-phase. You can buy a converter to make 3-phase from single-phase, but that may negate the price benefits of the machines.

[Ken Garlock]

Hi Johnathan. If you do not already have 3 phase in your shop, then there is no question, you go with single phase. Installation of 3 phase is an expensive undertaking I am told. You don't want to install a single phase to 3 phase converter. Here again as I understand it, a converter while a good answer for someone who has easy(inexpensive) access to 3 ph equipment, will introduce an additional loss of efficiency. It takes power to run the converter, TANSTAAFL. The best solution for the home workshop is to go with the single phase. Regarding the horsepower choice, I think you will have a hard time stalling a 3 hp. saw But, for the extra 10% for a 5 hp. it sound tempting.

So, go with the 3 hp PM-66, but no one would fault you for getting the 5 HP. On the other hand, you could get a Bridgewood 10LTS, and save a $1000.

TANSTAAFL - There ain't no such thing as a free lunch.

[Bill Turpin]

Single phase motors require start windings, start switches, and capacitors that are not necessary for three phase. Therefore they cost more. Three phase motors also draw less amps therefore cheaper, smaller wire. Most utilities have a limit on how much horsepower can be started at one time in residential areas. Motors above five HP will dim your neighbors lights. Installing 3-phase in a single phase house is a MULTIPLE thousands dollar project.

Bill Turpin in WNC mountains

[mike lucas]

It would be one thing to buy a 3 phase Powermatic,if you already had a phase converter. And chances are, you don't. Or if you found a really good deal on an old 3 phase table saw, then it would be best to go with the 3 phase.

I say get the 5 hp model 66 and be happy for the rest of your woodworking life. Do not worry about saving money and buy a much lesser saw. If the powermatic model 66 is the one you want, then get it! It is the best swa for the money of any 10" table saw anywhere.

[Rob Russell]

I agee wth most of what's been said about 3-phase. Installing 3-phase in a residential environment can be many thousands of $ if you don't have 3-phase on the street (like in our neighborhood). If you have 3-phase on he street poles, it's simply a matter of running another line. For such a case, I'd recommend a separate meter for your shop because that would allow you to leave your residential wiring alone.

The largest typical motor you'll find in single phase is 5 HP. There are 7.5 HP, single phase motors available on some machines (like Bridgewood's 15" open end sander), but that's not always the case.

You can get rotary phase convertors, digital convertors and Variable Frequency Drives which all provide different ways of producing 3-phase from single phase input. You can build your own rotary convertor if you wanted to. My european machinery is all 3-phase, so this is a bridge I've had to cross because 3-phase isn't available in my neighborhood.

On the PM66 - if you're not planning on upgrading to high horsepower machinery - order the 5HP, single phase saw. That'll guarantee that you never bog down ripping that 3 1/2 cocobolo plank with a full-kerf blade. Unless you see european equipment or similar purchases in your future, you don't need to go the 3-phase route. FYI, if you do ever go 3-phase - you can still run your single phase equipment as long as the 3-phase is 120/240v delta and not 120/208 Y 3-phase.

Just my opinion.

Rob

[Dale Thompson]

Jonathon,
My PM 66 has a 3 HP single phase motor. As has been said previously, 3-phase is usually reserved for industrial applications. Don't even THINK about it!

If you are a "hobbiest" like I am, go with the 3 HP. I have sliced 3" Oak with no problems. Much of the power used in your shop is used by the "start-up" requirements of your equipment. A 3 HP motor, on startup, will create less "peak power draw" than will a 5 HP.

If your saw is running continuously, "peak power draw" is not a problem. On the other hand, if you turn your saw on and off like I do, it can be a factor on your power bill.

Dale T.

[John Edwards]

Geez, what are you folks so worried about on this single vs. 3 phase issue ?

It DOESNT cost thousands of $$ to run a 3 phase motor in a single phase shop. Most all my ship is all 3 phase. From the 3 hp jointer to the 7.5 hp TS and planer. In fact I often run more then more machine at a time.

Ground rules are simple. A dedicated 220 line with a phase converter properly sized to the equipment loads you plan on running.

A static converter is the cheapest way to go. But is only about 75% effiicent. That means your 5 hp motor is gonna be putting out around 3.5 or so. Typicaly used on single motor apps. but can be used on multiple.

A rotary converter while being a bit more expensive to start with. Is a longer lasting, more efficent way to transform single phase into 3 phase. They typicaly run close to 95% efficency.

In both cases you run a single phase 220 line in to the converter and on the output side of the converter is your 3 phase.

Both are simple and if one was to do a search you would come up with plenty of examples of how to build one yourself.
eBay has them listed all the time. Great prices too.

[Doug Shepard]

I'll echo Dale Thompsons comments. I've got a PM66 3HP and have never come even close to stalling it or having it bog down. So unless you plan on cutting a lot of very thick or hard stuff, or just want know you got the top of the line, you can skip the added expense of the 5HP for home shop usage. Whichever version you get, you're going to love it!

[Jonathan Szczepanski]

Thanks everyone. It seems like 3 phase is just not worth the extra cost and hassel. I think I'll go with the 1 phase.

Of course now I need to save up the duckets for the saw.

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[Keith Starosta]

Thanks everyone. It seems like 3 phase is just not worth the extra cost and hassel. I think I'll go with the 1 phase.

Of course now I need to save up the duckets for the saw.

Ahh yes......money. Always the roadblock!!

Keith

[Rob Russell]

Geez, what are you folks so worried about on this single vs. 3 phase issue ?

It DOESNT cost thousands of $$ to run a 3 phase motor in a single phase shop. Most all my ship is all 3 phase. From the 3 hp jointer to the 7.5 hp TS and planer. In fact I often run more then more machine at a time.

Ground rules are simple. A dedicated 220 line with a phase converter properly sized to the equipment loads you plan on running.

A static converter is the cheapest way to go. But is only about 75% effiicent. That means your 5 hp motor is gonna be putting out around 3.5 or so. Typicaly used on single motor apps. but can be used on multiple.

A rotary converter while being a bit more expensive to start with. Is a longer lasting, more efficent way to transform single phase into 3 phase. They typicaly run close to 95% efficency.

In both cases you run a single phase 220 line in to the converter and on the output side of the converter is your 3 phase.

Both are simple and if one was to do a search you would come up with plenty of examples of how to build one yourself.
eBay has them listed all the time. Great prices too.

It can easily run thousands of $ to run utility supplied 3-phase to a residence. I do agree that 3-phase can be provided to a shop for less than that via RPC's, digital convertors (expensive but high quality power), static convertors, AC drives and VFD's

I'm still building my 15 HP rotary phase convertor (time and priorities have been my issue). There are considerations that make running a RPC of that size more complicated than running a smaller RPC. These include voltage sag at statup. I don't want to dim my neighbor's lights and without a redesign of the starting aspect of the RPC, that would happen. Balancing an RPC at different loads also becomes an issue - for instance if I want to run a 2 HP motor off of the RPC when it's really balanced for 10-12HP loads. My machinery has some electronic controls and I want to make sure the power from the RPC is well balanced between the 2 utility supplied legs and the generated leg. I may actually be better off having a pair of smaller 7.5 HP RPCs for my shop (or just go with the digital convertor and be done with it).

3-phase does add the complication of a 3-bus panel (more expensive than standard 120/240 single phase) and breakers are more expensive. You have to be careful wiring to not use the generated "wild" leg for anything except 3-phase machinery. Use a wild leg as a normal 120v leg and you'll fry tools.

[Paul B. Cresti]

I have all three of my main machines in my shop run off of a RPC. The machines hp's are 9.5, 6.6 and 6.6 I have them all run at the same time on regularly with out any problems. My RPC has a built-in voltage regulator to allow for the unequal load request in relation to its max output (max hp 15 max combined hp 45). 3 phase motors run cooler, have more power and last longer. A good RPC is very efficient. As others have mentioned you can build one yourself or buy one, there is no need to go to commerical power.