Hello
I have a chance to pick up a jointer and a mortise-tenon press for next to nothing as a local school is bulldozing its old wood shop. I’ve had a chance to look these machines over, they’re big, heavy rigs and seem to be in decent working condition. I don’t think they’ve seen much use in the last decade as the shop has been only used for rough carpentry, no cabinet making being done.
The only fly in the ointment is that both tools are wired for three phase power and I intend to put them into a single phase powered garage. I’ve done a bit of research and I’ve found reference to static phase convertors that might do the trick of getting me working. Does anyone out there have any experience dealing with this problem? I could use some sage advice about how to proceed.
PS I’m a casual woodworker (don’t wear a tie) not a production guy so the tools would only get occasional use.
yours, looking the gift horse right in the teeth,
Geoff
Replies
Dear G.,
Wouldn't recommend an inverter. It'd be more pradtical to replace the 3 phase motors with single phase motors at 220 V.
You can sell the left over 3 phase motors. Also, the converted machines would be easier to use and to sell when not needed.
It'd be OK if the motor are not the same HP as the 3phase originals. If you replace say a 5HP motor with a 2 HP motor, you'd still have plenty of power for use as you plan to give them. This is a guideline only. You'd have to make evaluation of actual situations.
You probably would need to get new pulleys to to fit the smaller motors. If they have starters (contactors), they probaly have coils at 120 V, so you'd be able to use those. If a starter or contactor is 3 phase, just one pole of it will not be used. Compared to the value of those machines, the cost of the smaller 2 phase motors would be low.
Those old machines are fundamentally great. You could also keep the original motors and all else for potential sale as 'original condition'.
-mbl-
I'll jump in and disagree with the previous poster. Get yourself a rotary converter and run them three phase. You can get a good one for $300-400 and it will really open up your equipment options. I've had mine for 3 years plus and it is no trouble at all to use.
Tom
Douglasville, GA
you failed to mention how the motors are attached, if the machines are direct drive it might be easier to deal with a static or rotary phase converter than try and change out the original motors. If you find yourself addicted to the older iron, this option will save much work dowwn the road.
TAKE THE MACHINES, TAKE THE MACHINES, TAKE THE MACHINES!!!
There are so many options to gettting that stuff running on single phase: rotary converters, static converters, vfd's, changing motors, etc.
There are many sites and sources for help in this matter. Don't let this slip away. If you are the only one that knows about it and the stuff won't get bid-up to crazy prices, it is a great way to get "lifetime" equipment.
re: static phase converters -
these work fine while they work, and they probably will work fine for a long time - - we ran a couple of refrigeration compressors with Ronk 'add-a-phase' converters, generally OK, but not no maintanance - relays wear out, capacitors dry out or leak, complex and wonderful - -
we are just finishing an addition to our public library, complete with elevator, powered thu a Ronk phase converter, they still use the same enclosure they used in 1960, but I bet the insides are improved - -
anyway, sorry for the ramble and free association, rotary converters are simple and cheap, electronic converters are expensive and easier to use until they quit working.
Dear David,
The cost of a rotary converter of course will depend on the HP or KVA rating. We do not know the HP of the machies he is buying.
Also, if the rotary converter you got was used, it might have been a special oportunity.
He also would have to add the cost of running 3 wires plus ground, and disconnects, panelboards, etc. to have 3 phase wiring, plus the wiring into the converter, plus the extra space the converter takes.
Also, it is less efficient to run a converter due to losses. But if the use is ocassional, efficiency and cost of operation is probably not significant.
If the rotary converter were to be bought new, for the HP rating of the machines, the cost could be unappealing.
-mbl-
well, as one of the lucky ones with 3-phase in my shop (gawd, I don't miss those add-a-phase units) my dealings with phase converters are in the past and I've never had a rotary unit - but my understanding is a rotary unit is little more than than an electric motor (availible for a small price compared to the electronic units) - you want to run your 3-phase equipment, start the motor (rotary converter) which generates the 3-phase current, then start your machine - - a little clumsy, but cheap and reliable
and really, the wiring issue is a wash, wiring in an electronic converter isn't going to be any cheaper than a rotary, and the same with power matching and space issues - -
indeed, if he has 3-phase power on the pole next to his shop, the best deal is to tap it and have the luxury of 3-phase...
upon re-reading your post again, I get the impression you are constrasting phase conversion with replacing the equipment motors with single phase - - and if it is easily achieved, it would certainly have merit - a big 'if'..."there's enough for everyone"
I have a phase converter in my shop that has never given me any trouble. Also if you get one...get the next bigger unit as it will open up doors in the future if you should ever want another 3 phase machine. You will no longer be limited to single phase machines. There is also the promise that you will find another prize machine that you want....the 3 phase will not be a issue.
Wow,
I've been long time lurker on this site, enjoying helpful hints and wry humor for sometime, but I've never really had a question until now. I am astounded by the quick and knowledgeable response my inquiry has generated. I am certainly taking the machines - in fact I have a buddy helping me get these behemoths into a truck today so say a prayer for my back (bend with the knees, bend with the knees!).
I think I'm going to go with some sort of phase convertor - rotary or static - a lot will depend on the prices I get quoted. Unless it proves to be much cheaper than I expect I doubt that wiring my garage for three phase power makes a lot of sense and not really into trying to swap out the old motors (I'm not the most mechanical able guy).
So thanks again. I kind of expected well-informed insights from this forum, but what really impressed me was the generosity and warmth of your replies.
yours
Geoff
1066? Harold? Norman? Have you read that wonderful history book, 1066 and all That?
At the very least this curious mind wants to know the reason for that numerical appendage.
A very astute observation Ed,
As you very well know 1066 is the only memorable date in English history and therefore a handy way to make a login id distinctive without ending up with a numerical porridge at the end of one's name.
Yours, the guy with a lot of short hairy ancestors who endured the damp of Northumbria,
Geoff
Wait! Wait! 53BC!! That was an important date too. And, and, even if the Eaton/Harrow match didn't make the cut, it almost did, if I recollect correctly. (That was a really funny book, back when I really knew the ancient saga of the British Isles.)
Now, do you know Grand Prix du Rock as done by Peter Ustinov?
indeed, if he has 3-phase power on the pole next to his shop, the best deal is to tap it and have the luxury of 3-phase...
-David-
...
Yes, friend.
This is the simplest option and less questionable one. The option of changing motors is strictly as compared to using a converter for places where 3 phase lines are not available.
Converters are meant for areas where the utility does not have 3 phase lines nearby, such as rural areas. But that is mostly past history.
Properly done, even with a converter of any kind, 3 phase wring would still have to be run to the machines. That is means to protect and disconnect the cables and loads. That usually be 3 phase breakers nowdays, i.e., some panelboard.
Once a panelboard is installed and 3-phase wiring is ran to the loads, the majoity of the wiring is done.
That means that the utility could easily drop a meter and service to that panel. No modifications to the machines would be required, and they could run at full power.
This would be the most correct aproach.
-mbl-
Edited 5/19/2004 11:12 am ET by mbl
Repeating Jim, take the machines
Think of it this way... you're getting some great machines for very little. Invest your machine savings into rewiring your shop for 3 phase power. You'll never regret the extra amps
as you can see, there are alot of opinions on the use of phase converters versous single phase motors.here's my take on it, considering that I have been using phase converters for the past 10 years.
Buy a rotary phase converter, not a static. On a rotary converter, you use lose about 10% of the "horse power". On a static converter, you lose about 30-40%. Depending on the type of machine, as in a compressor or a power feeder, the machines tend to run a constant load and a static converter is not sufficient to run these types of machines and will burn up the motor quickly. I know this from personal experience. It cost around $500 to have my power feeder motor rewound.
Three phase motors have a smaller frame size than single phase motors. Most motors that are 5hp/3 phase are about the same size as 3hp/1 phase motors.
Buy a rotary converter around 20% larger, or the next size up from the largest motor you have. a rotory converter can run up to 3 times the amount of horse power. So if your largest motor is 5hp and you have a 5 hp converter, you can run around 15 hp of combined motors at any given time, as long as they are not all turned on at one time and none of the motors excede the 5 hp limit individually
I'll enclose some photos of my temporary setup in my garage.
The panel on the right is a single phase sub panel that comes from the main panel in the home.
From there it goes to a three phase power disconnect ( the center panel in the first picture) The power goes to panel from the top. The power then goes through the fuses and supplies two leads to the pase converter through the bottom of the center panel. the phase converter then generates the third lead and sends it back to the center panel.
From here, it to goes to the next panel on the right hand side of the photo. This is the three phase panel that then supplies the power to the breakers for each circuit
This whole set up as you see is temporary until my shop is moved to it's new home. If you look at the wire sizing, it is a little backwards, but it is sufficient for what I need at this time.
The last photo is of the 15hp rotory phase converter. I think it weighs 125 lbs
If you try to go the route like I have, the panels will cost in the$200-$300 range. if you can find an used/salvage electrical house, it should run less than $100. The 15hp rotory converter runs aroung $1500.
Try contacting Phase-a-Matic in Palmdale, Caifornia if you need more info. They have been a great help over the years The biggest thing to remember is that most three hase motors have a magnetic starter switch. and this switch is usually single phase. Do not attach the "generated leg" to the starter switch. You could burn out the switch. The easiest way to determine which leg is the generated leg is to measure it's voltage seperatly. The generated leg will measure some where around 220-220volts, where the 'origional" legs will measure around 110-120volts each
Dear friend,
With the static phase convertors, and the rotating convertors the three phase motors are not running in true three-phase voltage.
That meaning that the phasors are not truly 120 degrees appart. With some static convertors, they may even be running the 3-phase motors single phased, where the electronics and some capacitors are doing the equivalent of what can be done by hand: hook a 3-phase motor to two lines, give the shaft a slight rotation, and it starts spinning.
Those conditions are not adequate for motors, due to unbalances and they would damage motors if they were to be on continuous operation and at their ratings. That may explain yor burned-up motor.
The reason those devices can be used in small shops is that the motors on most woodworkng machines do not run at their rating for prolonged periods of time. It is not true that those convertors have the capacities implied.
There are two types of starting currents: One is starting current of a motor UNLOADED and the other is starting current LOADED. The machines in a shop seldom start loaded and are seldom run at full load, much less for continous use. The claims of the sellers are based on those conditions, but not on real HP ratings. It is somewhat like some compressors HP ratings that have now been outlawed.
Even an unloaded 3-phase motor will suffer damage to its rotor windings if it is left to operate continuously on single-phase or unbalanced voltage conditons. That is due to the flow of negative sequence currents in those windings.
The above does not mean that those devices do not have practical uses. But it is important that it be understood that those uses are limitted.
A good check for claims is to see if the devices have a UL (Underwriters Labs) test label. If they do, they might be classed as for emergency use, or temporary applications.
Best wishes.
-mbl-
Edited 5/20/2004 9:44 am ET by mbl
At the risk of creating "yet another old arn addict", you might want to dabble a little bit in/on/at the OWWM ConGlomCo of Web pages.
OWWM, The Forum (where it all started)
http://finance.groups.yahoo.com/group/oldwwmachines/
OWWM, The Web Page (where we post pictures and articles of our "dandies)
http://owwm.com/
The OWWM is one of the few places where I have seen 'lektrikal questions asked and received replies that don't/won't lead to someone getting themselves killed. Not that there aren't good answers in this thread/on this forum, just that there seems to be a better ratio of knowledge driven replies there as opposed to people who answer with "what they've heard".
(Full Disclosure Insert)
I am the founder of the OWWM Forum Site and list Mom and I do tend to go on a wee bit about it here and there.
Keith Bohn
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