3 phase problem

[forgeblast]

Just wanted to share a Doh! moment. A friend of mine wanted me to forge him a dagger/knife. He has metal from his dads workshop but its 1'' thick. The blower i currently have on my forge is good enouch for the thin stuff but i need a larger blower for this. So i ordered one, well i thought great its 125 cfm, 120 vac thats what i need. What i didnt read was 3ph. Didnt even see it, but its right there.
So my question is its a 115v 60 hz .6 amp electric motor
whats the cheapest way to go about using it on a standard household current. I was thinking an inverter? any suggestions, besides getting my eyeglass prescripion upgraded. /forums/images/graemlins/laugh.gif
thanks in advance
forgeblast

 

[chim]

The info you provided isn't clear to me. Please have a look at it and verify. You said the motor is 3 phase, but also said 120V / 0.6A. If the CFM is correct, I wouldn't suspect a 3 phase motor is needed. I'm missing something..............chim

 

[CT_Tree_Guy]

forgeblast, something also sounds not quite right about this. Most (all?) 3PH stuff I've seen is either 200V, 208-230V, or 460V, (and is there a 600-something volt?), but never 115 volt. It takes just one "leg" from your main panel to get 115 volts (speaking very generally here), so I have to believe that motor is single phase. A picture of the faceplate from that motor would be very interesting to see.

And it is IS 3PH, I wouldn't bother with a converter. They are fairly expensive, and defeat the efficiency that is gained by running a 3PH motor on real 3PH power. Best just to return the motor and get a single phase.

As always - if I'm "all wet", please forgive me. /forums/images/graemlins/smile.gif


John

 

[bobodu]

I get enough heat just from the draft on my wood stove to get near weld heat!! Very bright yellow on 1" round.
Have you tried your trusty shop vac?

 

[heehaw]

if you don't exchange your blower, and really want to try to use 3ph: i'll look around and find the article i have that explains all that stuff: you can us some capacitors to change the phase of one leg or another motor in series, i've seen it done a lot, because used 3ph motors are usually really cheap compared to single phase...
heehaw

 

[Farwell]

If in fact the motor is a 3 phase motor it would be cheaper to replace the motor than to purchase or build a phase converter. Go on line to the Grainger site and try to find a 115 volt motor of the same horse power that will replace the existing motor. If you can not purchase from Grainger take the information to a local supply house and have them get one for you. Or, as someone else wrote, try a shop vac to see if it will do what you need.
Farwell

 

[SPIKER]

Hi there:

like others said, 3 phase is 240 vac or 480 vac, not 120 vac. 120 is single phase. now that you have it if it IS a 3 phase then you can buy a Frequency Drive which will run on 220 vac single phase and provide 240 vac 3 phase. redily available but slightly expensive, in the $200 plus range.. for smaller applications.

there are some small fractional HP motors which can be controlled using different hook ups caps & inductors to provide a offset frequency... that said it is not somethign for a novice suer to be albe to setup. best bet is to get standard single phase motor & retor fit or send it back to et the right one.


mark M

 

[bher]

Get a variable frequency drive. Should be able to find one pretty cheap on Ebay. This will also also you to control the speed too--very handy.

 

[forgeblast]

I wish i could return it, i made some modifications to the blower before i messed with trying to put a plug on it. So at this point its mine. /forums/images/graemlins/grin.gif The blower i have works fine like i said for small stuff and the noise level is perfect, the shop vac would drive me crazy with all the noise it puts out. I used a vaccum cleaner motor to melt aluminum in college, we did some styrofoam vaporization casting. I have bid on a inverter on ebay and the variable frequency drive looks like a winner too if i dont win the inverter. As for the motor i will write down everthing thats on it when i get home from work. I do know that the power wire coloring that comes off of the blower is UK.
Thanks for all the help,
forgeblast

 

[billbill1]

Mark, I had a 3phase 115v motor on a conveyor where I used to work. I had never heard of such a thing until I saw it. We ran it with an inverter that was 480 primary and 115V 3-phase secondary. It sounds weird but it's out there.

 

[CT_Tree_Guy]

Bill -

After posting that I'd never heard of such an animal as a 115V 3-phase motor, I poked around on the internet until I found one. I tried to find some info on how the heck one works when wired to a typical 3-phase panel, but came up blank. Can you shed any light on how the heck such a motor works, and how it is wired to a 3-phase panel?

Thanks, John

 

[Spiffy]

I'm all wet on electrical advice occasionally too, but I see no reason you can't go with an idler motor like plenty of people do with 240V single phase.

I've seen pages with better drawings; also, discussed here before too I think, but this one looks to describe it pretty well:

3ph idler

It does mean you'd need another 3ph 120V motor.

 

[RedRocker]

A three phase motor will run on single phase, you'd just have to rope start it when you want to use it. May not be the best solution but it doesn't cost anything.

 

[forgeblast]

Hi all, this is what the label says.
eastern air devices dover, n.h. usa
115v 60hz .6a 3ph (blank) hp
3000 rpm (blank) mfd (blank) vac cl (blank) (blank)
pn b53a7l cont duty 4 8 6 8

http://www.surpluscenter.com/item.asp?UID=2006013018151456&catname=&qty=1&item=16-1051

(this is a pic of it).

Later and thanks for the responses
forgeblast

 

[billbill1]

John, I believe that these motors are used for speed control with the use of an inverter. Baldor makes an inverter that converts 480V 3 phase to 115V 3 phase. Inverter duty motors are much more rugged and can be ran down to 15 hertz where a normal motor shouldn't be ran below 30 hertz (if I remember correctly). Not a good explanation but it's all I have.

 

[CT_Tree_Guy]

Bill - Thanks, that sounds very reasonable, and is a whole lot more info than I had before. /forums/images/graemlins/smile.gif Makes good sense now that you've got me outside of the little "box" I had my thinking stuck in; namely, that the motor was somehow going to be wired directly from a service panel. Couldn't quite wrap my pea brain around that one! /forums/images/graemlins/tongue.gif

Thanks again, John

 

[Spiffy]

That converter would be sweet.

I have no idea how much power that fan takes, but if it's a fraction of the motor's rated output, RedRocker's suggestion would be the simplest. I think you lose about half your torque in this mode [I know logic says 1/3; maybe that is the case /forums/images/graemlins/confused.gif] It's rated continuous and you're looking at a few hours here and there, so I wouldn't worry much about too much current for the windings.

If you don't mind the "jumpstart", the next simplest would be to get another identical motor, or any 3Ph 115V motor larger: wire all three leads to the respective one between motors and your hot and neutral lines to two 2 of them. You wouldn't need any fancy capacitor wiring like the link I posted, but might need to spin the idler motor to start it.

Disclaimer /forums/images/graemlins/tongue.gif /forums/images/graemlins/grin.gif : I've always found another way around it, so never actually tried this; second hand info and a few web sites, but it does make sense, also all the web sites I'ved searched at one time or another have the same basic premise; just variance on how to start the idler.

Good luck whatever route you choose! /forums/images/graemlins/cool.gif

 

[JRP]

Soultion 1: Abondon the blower and look for another source of air - leaf blower or vacuum cleaner?
Well, if I had to get a bigger blower for one project I'd use my echo PB2000 leaf blower. It also is a teriffic shreader cleaner. A $5 garage sale canister vacuum cleaner might also work.

Solution 2: Inverter
A small variable speed drive would give you the ability to dial in your desired blower rate. Many small drives can also run off single phase. You must check the instructions, as some drives have loss of phase protection and will shut off if it detects one phase leg is missing. You mus "derate" the drive, which meqans buy one larger than your motor nameplate rating. A rule of thumb would be to make sure to double the drive hp rating. 120v 3 ph .6 amp = 125 watts = 0.17 hp. If you got a 1/2 hp rated drive you would be fine.

The next problem is that 120v 3 phase drives are not common. You would have the best luck with getting a 240v drive and stepping the voltage down to 120v using a 480/240 transformer. When you connect the 240 to the normal 480 v input 9primary), the output (secondary) will be 120v. This must be a three pahse transformer which is not as common as 120v control transformers.

By code you should also have an overload relay. Most important, make sure the forge and blower are well grounded. This will make sure the breaker trips should something short.

Overall, the alternate blower would be an easier solution. You can't beat an Echo PB2000 blower. It does have a variable throttle.

 

[bobodu]

I just hate the thought that you may end up throwing good money after bad.Borrow the wife's hair drier...
I have welded 1' square with charcoal and a Sunbeam.

 

[forgeblast]

Well i gave in and ordered a new blower, it wasnt that it was that expensive just i hate having one that i cant use. How did you figure out the horsepower of the motor by knowing the v and amps. is there a formula?
thanks all for the help,
Forgeblast