Rotary Phase Converters?

Michael J. Spangler

Michael J. Spangler

Joined
Oct 8, 2003
Messages
2,181
hey guys whats going on? this one goes along with my other thread.
i'm also in the market for a rotary phase converter for a motor bwteen 5 and 7 horse. I know these things get expensive, is there any good place to keep an eye out for them? thanks a lot guys much appreciated.
I need to get this hammer up and running. its been sitting way too long!
 
hey i guess i should also ask... is a rotarty needed? or will a static hold up? i hear they burn out. not worth it for the $$ right? thanks again
 
Hi Michael, I had a static convertor...and burned up a Bridge Port Milling machine motor with it. After studying them...I learned tha the static convertor was just a capacitor to start the motor..then it ran on 1 leg. Keep in mind that 3 phase motors have 3 legs..so you only get 1/3 power. It is my opinion that the static convertor companies use some clever verbiage in their marketing to make you think otherwise. It is my opinion that they are junk.

Then I built my own rotary convertor base on plans found on the web. It was very educational and fun....and worked like a charm for several years. It was a 3hp set-up. Then I bought a 10hp rotary convertor off of Ebay. I think I paid about $600 or so..maybe 8 years ago.

You have a few choices to get your power hammer running. From your other post...it sounds like you need a motor for it...if so, why not just buy a single phase motor for it?.. Then you don't need a phase convertor.

If you do need a phase convertor, you could also use a VFD...one that accepts standard single phase input with 3 phase output to run your hammer. The nice thing about this is that you will also get motor protection and variable speed if you want it. Or you could just use it to run at a preset speed all the time. Based on my rotary convertors, the VFD will provide better 3 phae power that is cleaner and more balanced across all 3 legs. Rotary convertors fabricate the missing legs with banks of capacitors and the leg phases were not equally spaced at 120 degrees apart...nor was the current draw across the the different legs. I tried to balance it the best I could...and it actually ran fine.

I'm guessing that a 5-7 hp VFD will cost less than a rotary convertor.

These are just some thoughts that came to mind as I was typing. Good luck and have fun with your project.

-Rob
 
i have a friend who made a converter from an old motor to run his huge bandsaw. he had to pull start the converter motor before starting the saw but it worked pretty good. he still uses the same setup i do believe. if he still does, i can ask how he done it and maybe take picks.
 
Michael, I have to agree with Rob. I work with this stuff everyday. Static converters aren't worth the money and rotary converters can be pricey but do work ok.I would go with the VFD if you can find the right size and configuration.Some of the manufacturer's limit the single phase input at around three hp, so you might have to go to a rotary. It will do you good to research some.Dave:)
 
awesome results guys.. thanks a lot

i like what i hear.

the reason i'm going with 3 phase is because the motors are inexpensive for their size... and as far as i've heard they're work horses that don't burn out as easy as single phase motors.

but then again i don't have anything to back this other than hearing it.

so i checked into the anderson converters they have a 7 1/2 HP converter for sale for 559 might be expensive to ship it here though... but that seems like a damn good deal. i'm going to have to call them.

so were would i find a VFD that could work? and how does that differ from a static converter? thanks again guys keep em coming....


p.s. rob frink i need to mail you about something

p.s. richard shoot me an email.. sorry my phone keeps messing up every time you call
 
Mike, take a look at ACTech VFDs. I used one on my grinder and it's a nice piece of equipment at a decent price. If you find a model that'll suit you, just look up your local retailer from their website. If you can't find one, let me know, I've got one down near me and could ship stuff to you.

Also, if you still need info on the helve arm for that hammer, let me know. I was chatting w/ Ray Rybar a few weeks ago and he may be able to help.

-d
 
deker you the man... actually i talked with rob frink and he talked me into a single phse motor...

any chance you have ray's contact info?? i can't find it for the life of me. shoot me an email if you do. thanks deker i owe you
 
Micheal

What sort of power supply to you have available in your shop (current and voltage)? Assuming you have a 15 A 230 V supply, the most power you can get is 4.6 electrical hp out of your utility. A 20 A 230 V supply will give you 6.1 electrical hp. Due to inefficiencies in the motor, you will get something like 80 % of these figures at the motor shaft. Do you really need 5-7 hp for your hammer. If not, you can get a simple single-phase motor, like Rob has recommended.

Rob is right on about the differences between a rotary converter and a VFD. I would add that a rotary converter would most likely be physically larger, heavier and noisier than a VFD, especially for one in the 5-7 hp range. Your electricity bill will most likely be higher if you use a rotary converter. The input-output efficiency of a VFD should be better than 90% whereas the rotary converter might be somewhere around 60-70%. Our Motor R&D Manager also said that your motor will run hotter and be less efficient if it is connected to a rotary converter.

It should be possible to use any VFD with a single-phase input. With a single-phase input, the VFD's input current will be 1.73 times higher than the three-phase input current. Some VFDs are designed with beefed-up input rectifiers so that they could be used with a single-phase input with no derating of the output power. Those without beefed up input rectifiers can still be used with a single-phase input but the output power that is available is reduced to 57% of its normal rating so you don't blow up the rectifier. For example, you will need a VFD rated for at least 8.5 hp to run a 5 hp motor. I would expect that the cost for the 8.5 hp VFD should be less than 1.73 times the cost of a 5 hp VFD, i.e. the $/hp ratio should fall as the hp increases.

The 3 hp "limit" that Dave mentions is due to the fact that industrial users ocasionally use a single-phase supply when the motor is 3 hp or less but would always use a three-phase supply when the motor is over 3 hp. Thus, none of the manufacturers bother putting an input rectifier rated for single-phase operation on VFDs rated for more than 3 hp.

If you do decide to go with a VFD, either get one with a NEMA 4 enclosure like the ones that Rob sells or mount it so that metal dust will not get into it. The reasoning is the same as for using TEFC motors instead of open motors.

Have a great Turkey Day!

Phil
 
I would agree on the single phase thing. If you are already wired for (and stuck paying the demand rates for) 3 phase it is a beautiful thing to run motors off of, if you are buying a new motor go single phase and count the money you save. I have a 5 HP single phase metal lathe that was custom built (the LeBlond Regal 15C5 lathes were typically only available in 3 phase) and the thing is almost as old as I am and has never had a problem.

-Page
 
ahhh tooo much info!:D thanks guys you rock. i think i'm just going to go with the single phase... well worth it for me instead of dealing with all that junk.

i guess the 5 HP motor will be plenty to run the hammer i have.

now the question is do i go with a WEG motor or a lesson??? :D

https://www.surpluscenter.com/item.asp?UID=2007112112511552&item=10-1435&catname=electric

https://www.surpluscenter.com/item.asp?UID=2007112112511552&item=10-1323&catname=electric

https://www.surpluscenter.com/item.asp?UID=2007112112511552&item=10-2295&catname=electric

thanks again guys

deker i did get a hold of ray i'm all set now thanks
 
Michael J. Spangler said:
deker i did get a hold of ray i'm all set now thanks
Click to expand...

Cool. I was just going to point you at the ABS directory for his number ;) If you ever get to the Phoenix area you should stop in and visit with him. Heck of a nice guy.

Now, get that hammer running mister!

-d
 
Micheal

Do you really need 5 hp for the hammer?

Of the motors that you linked to, I would suggest one of the TEFC motors since you may have grinding dust floating around. Both the Leeson and WEG seem to have similar features and specs. The Weg is made in Brazil. I hear that it has a decent reputation though I have only used one to test my motor drive. It may just come down to price.

Phil
 
i think i do need the 5 horse for it. i know the 50lb hammer suggests a 5 horse according to the old manual i have. but the 30lb recommends a 3 horse... so i figure the 5 will work fine.

i think i'm going to go with the leeson... now i just need to find info on the beamof the hammer so i can get that made and get this thing pounding steel.

thanks guys
 
as long as you teach me a thing or two about forging.. and promise we can make a sword while you're here you're welcome

ahh heck you can come even if you don't do any of that:D
 
Ohh you got yourself a deal! all a sword is is a big knife:D. Plus i still owe yah for that neat little kiridashi.
 
too many descisions i need to go to bed.
hope you all have a good turkey nap tomorrow. take care and thanks for the help

mace....




.......:eek:BACON!!!:eek:
 
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