All Replies on Old three phase motors and Variable Frequency Drives (VFD)

Topamax, just a question. Was the power in connection Delta or Wye? Only asking cause I’ve seen some high phase Delta here that does some weird stuff to old machinery. Don’t know that much about it, but I know an industrial electrician who has run into three phase motors that acted just like you explained. Like a dead short.

Same thing, close or not so much?

-- Methods are many,Principles are few.Methods change often,Principles never do.

All most all pwer connections are Wye these days, at least here in Water World.

The motor is does have a dead short at the voltages teh drive is butting out.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

VFDs introduce transients with extremely fast voltage rise times into the circuits that can quickly destroy the insulation in older non-inverter duty motors. There have been many motor design improvements since VFDs came on the scene once it was apparent that drives are here to stay. Inverter duty motors have design changes like increased winding slot insulation, increased first turn insulation and increased phase-to-phase insulation to withstand peaks of up to 1600 volts. Another frequent mistake made is slowing older motors down below 1/2 rated speed (<30HZ) which creates overheating due to the motor fan not moving enough air.

Your vocabulary is too copious for my immediate comprehension, please illusidade!

-- $tudie

I tried to keep it as simple as possible. Bottomline, you are always taking a risk putting a drive on an old motor. Sometimes you wins and sometimes you looses ;-))

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Ahhhhh, my good friend, unfortunately it is pretty much like tossing a coin in the air and picking heads or tails.

That’s the nature of the beast.

Happy Easter to everyone….

Tanks Tomamax, I wuz just axin’ fur my own persuites.

-- Methods are many,Principles are few.Methods change often,Principles never do.

25 years ago VFD’s were very new. The motors built for that time usually were made for the standard 50-60hz operating range. A good VFD can be infinitely adjusted from 0-120 hz. THose old motors will not take it. Trust me, been there, done that. Im just wondering where you are using a VFD in a woodshop? Im always in for great ideas and i have access to all kinds of drives.

It may be a little different to the US, but over here in Ireland i’m using a 4kW Omron/Yaskawa V1000VFD to step up the rpm of the 3 phase 50Hz motor on the Bill Pentz dust sysytem i’m building from the standard 2 pole 2850 rpm to the 3,450 rpm you get on the US 60Hz motor the blower was designed for.

The variable speed is incidental so far as i’m concerned, it’ll be set and forgotten. The VFD does have some other advantages however from what i’ve read in recent weeks though:

1. The programmable soft start the VFD almost eliminates the additional current drawn by the motor on start up. (it would draw six times the full line current if started normally DOL or direct on line) This is important for me as i would otherwise risk popping the incoming 62A fuse on my 220V single phase supply.

2. A decent VFD gives very high levels of protection in the event of overloading and so on. It also avoids the need so far as i know for an NVR (no voltage relay – drops the contacts out for safety in the event of loss of supply) in the starting switch as it contains this function.

3. They give more or less full torque right down to the lower RPMs – but you need to be careful about the limited cooling that results from lowered fan RPMs.

The downside my supplier said is that it’s not reckoned to be a good idea to run a cheap eastern or old motor with one, presumably because of the insulation and other extra stresses it can result in if run over or under the stock RPM.

It also happens that for the majority of single phase to three phase VFRs that don’t step up the voltage (i for example am getting 3 phase power at our single phase 220V – instead of the usual 380V) you need a dual voltage motor connected in delta. This isn’t an issue for most modern motors, but older and cheaper motors may not have this facility.

The reason for this is that to get the same HP at 220V as 380V the windings have to handle a much higher current – which in the specific situation where old three phase motors are being run on single phase power via an inverter without a voltage step up transformer is presumably the reason they often quit.

Don’t ask any complicated questions as this is just what i’ve gleaned in the past week – i’m no expert!!! :-)

ian

-- Late awakener....

Also older model Delta Lathes had VFDs on 2hp motors that ran off 110volts. I had a b*ch of a time trying to replace it when it went too. Had to buy a whole different system and run it off a 30 amp ac line. But at least it work and works good now.

-- (You just have to please the man in the Mirror) Mike from Michigan -

notottoman You can have the motor checked with a mega-ohm meter. They operate at high voltage. If it doesn’t read close to infinity, the motor will probably not run with a drive.

ToddTurner IMO, drives are getting so cheap, they make roto-phases and converters obsolete. They are so much more versatile.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

It’s all geek to me.

-- Mike, American in Norway

New to this chat room and although not really a woodworker myself, I am an electrician who helps a lot of my cabinet building and blacksmith buddies with the ancient equipment that they pull out of barns around here. I am trying to find help about a VFD problem Im having with Chinese equipment in a brewery that I’m doing some work on. Its a 4.4 HP 220/480 volt Chinese motor transmission assembly that has been making a clanking sound when wired in the lower voltage ( Delta) configuration. This matches the system voltage which is a delta High leg. The drive operating this motor is a 5HP drive from Automation Direct. The unit operates poorly and will fault out on overload after a short while. However when this same unit is wired in the Wye configuration it operates properly with no noise whatsoever. I was impressed with the expertise I have read in this thread and was wondering if you could help me with this problem before I go bald from scratching my head

That is wild!! :-)) I’m not sure, but I would suppose it has something to do with the high swiching ferquency of the drive that is se the ground fault wired delta. Any reason you can’t just wire it wye and forget it?

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Yeah my intuition on it is that its causing some sort of ringback noise from the motor. A pal of mine has suggested an inductor on the output as a filter but before I start throwing extra parts on the system I would like to know why its doing this. We can and will run it in Wye but there is HP loss when you do that and the german in me tells me that its not proper to run a device differently than its designed for. Seeing as we have several of these out in the field I would rather be prepared for the next time this comes up

What is it, 12 lead motor?

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Not sure Good question The Peckerhead of the motor( The lead junction box) has 6 studs with interconnecting jumpers plus three motor leads coming off of it . I think its a 9 lead motor

Not sure how you are making the connections from Y to Delta. Sounds like a single voltage motor. Not likely a motor that small was ever intended to Y start Delta Run: therefore, maybe a dual speed?? If you are using a VFD, you are getting variable HP with the variable voltage. You aren’t really losing anything going with Y unless you are running at full voltage. Most drives can be operated at 125 to 150% if you need to get it back up. I would either run it Y and monitor for overheating which probably won’t happen, but could. Or, forget it and put a VFD rated motor on before I started buying parts and expending labor. You will not fool the electronics in that drive. The switching is in the mega Hz range just fooling the motor into doing what the drive wants it to do.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Top,

Dang boy, you are smart!!!

Steve

-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

Steve, Haven’t made up my mind on mine, only 41 years ;-))

Not sure I’m really that smart. This isn’t rocket science ;-) Suppose I could have been a rocket scientist. But, like my son said when he was deciding his career choices in pre-engineering, Aeronautical is so complex he just did not want to deal with it every day for the rest of his life ;-)) Neither do I. Just pain lazy I guess:-) and too lazy to get up and report to employees everyday. Just do it myself.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Top,

That’s the great thing about this site; the depth of knowledge is breath-taking. Not just in woodworking. To find a discussion this erudite on a site such as this is amazing. You must be really good at what you do.

My interest was in converting 3 phase industrial motors to run on house current. Some sites propose build-it-yourself vfds, but the English in me said no way. There are a lot of saws out there at auction (maybe you hadn’t heard about the little economic blip) but they all have 3 phase motors. I’ll pass for now as I wish to stay married.

I allways enjoy your posts, hope you feel well (you know that the CDC is now using lawyers in some of their experiments? Seems there are some things a rat just won’t do!), your family is safe, and you all have a Happy Thanksgiving.

Steve

-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

Steve, You can build whats called a rotary phase converter by getting an oversized three phase motor and running it with no load on it. I’ve built plenty of these and they work very well and are inexpensive compared to getting a VFD to do the same job. It works by starting what we will call the generating motor with a smaller motor using a belt and pulley or drive wheel directly to the shaft of the generating motor. Once the generating motor is up to speed you apply 240 volts to two of the three motor leads and remove the drive wheel or belt. We recently did this by having the drive motor on a hinge set up so that you can take the tension off off the belt and slip it off. At this point the generating motor will run by itself and create a third phase on the unused lead. The only caveat on this is that the generating motor should be oversized by about 30% , Meaning , if you have a 3 hp tool you need to run then use a 5hp generating motor. The tool can remain hooked up to all three leads of the generating motor and will run fine. There are some VFDs that will convert single phase to three phase but they too need to be oversized and can get rather pricey when trying to run larger tools whereas you can often get old three phase motors for free. There are all kinds of websites about this

Yup, it works, pretty good unless you are starting motors under full load; ie, compressors or pumps. In those situations, expect to burn up the motor ;-((

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Good point , The compressors can be used as long as they have a decent unloader valve on them but I would Oversize the motor in that case. Pumps need a capacitor bank as well as the RPC but I would find a single phase pump before I would try to run it in 3 phase

Better size those overloads tight or you’ll still be buying a new compressor motor. Jury riggin’ works well for low intermittent loads like table saw, lathe, ect but not heavy continuous. I have been through this several time with people not wanting to spend any money but they know a guy that will make it work cheap. Then they call back wanting to know why the motor won’t go round and round any more ;-)) It’s because you let the smoke out! Electrical devices only work with the smoke contained inside, once it is out, game is over ;-((

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Turns out the motor in question may have larger issues. At the proper voltage it draws TWICE the nameplate amps. Its now being sent in for repair and i suspect that it wasnt properly configured internally. We will see.
FBCA

Glad I’m keeping you entertained Steve ;-)) There are a few people who seem to have very high expectations of me. Your comment reminds me of a few of them. Years ago my employer sent me to Anchorage to repair one of the loading ramps that drive up to planes or loading and unloading passengers. The shop gave me tickets to go and return the same day. I didn’t think much about it, I had fixed a lot of them at Sea-Tac for several airlines.

When I landed in Anchorage, the airline’s person met me. He said, “We’ll get your baggage, then I’ll show you the problem.”

I replied, “I didn’t bring any baggage.”

“You didn’t bring any baggage? You come to Alaska without baggage? We have been working on this problem for several weeks. A little over confident aren’t you?”

I replied explaining that if they needed parts there was no need for me to wait, they could put them in and if not I would have it fixed. My return flight was at 5 PM Anchorage time, but I was not on the plane. I was closing up the cover of a control panel as I watched my flight lifting off the tarmac. They had an issue with a 2nd Jetway. Since I had a couple hours to wait, they wanted me to take a look at it. Next plane back to Seattle was about 7 PM ;-)

I have identified the problems and repaired a lot of issues that have left electricians and engineers at a loss for years in some cases. It never took more than a day unless I had to do a lot of design work.

One of my friends told me all apprentices should be like me when they turn journeyman. He spent a lot of time in course development to train them. Another who was my 3rd year apprenticeship teacher had a series of progressively difficult problems to teach motor control. He asked if I wanted my paper when he was handing them back to the class. I told him not necessarily. I later found he copied them and handed them out to future classes to study. He told me he didn’t know the answers, but figured the class could figure it out. He said he got lucky. Not only did he get a kid who could figure it out, but drew text book quality diagrams to boot. He got a reputation for his motor and control class and was requested to teach at a local community college which he did for many years. Last time I saw him he told me his whole teaching career was based on those drawings I did when I was an apprentice;-))

I have been very blessed with this ability and very fortunate to be born in America in the 20th century. Today is the day to give Him thanks for all our blessings. I am very grateful and hope you all have a Happy Thanksgiving.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

paleoelectronics, Just curios, What does it draw no load?

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

I currently have 2 motors running on VFD’s and they have been for the past 2 years. I have not had 1 issue so far. I am planning on adding another VFD to my lathe for the variable speed capability. It just makes sense. The 2 others are currently only being used for their 3ph conversion factors. They are both single phase input and 3ph out, one is 110 in and the other is 220 in. In wiring the VFD there cannot be any type of switch between the VFD and the motor of the motor and or drive will go belly up. ALL of the switching has to be BEFORE. Both of my drives plug into the wall and a momentary switch to control the VFD. I have not heard of anyone having trouble with older motors and VFD’s. I wonder if the motor was going bad and it may have possibly been re-wired wrong

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

In the majority of VFD applications to existing equipment, most users are specifying motors to be changed out to VFD rated during the upgrade. There are a lot of old motors that are failing with the addition or will fail shortly after the addition of a VFD. The insulation is not up to the tasks at hand. VFDs on old motors are a crap shoot. Just because you haven’t seen them doesn’t mean they are not failing to start. Usually the drive faults and will not run the motor. I get to break the news to the young guys on the jobs when they wonder what their meters are really saying after they add a drive to a motor that was running just fine with an across the line starter ;-))

In my experience, the 10 mega ohm reading with a high voltage meggar most manufacturers used to say was a good motor is in the process of failing even when just operated at full voltage, constant speed.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Odds are, the motor you mentioned in the original post already had a fault to the frame. Unless the shop has ground current detection (most don’t) they would never detect it and motors can run for years like this. With the motor case grounded (most are) this isn’t even a dangerous condition.

The high voltages you mention are primarily due to transmission line effects at the switching frequency. The most you will see is twice the line voltage so, for a 480V motor, yeah about 1000V. Considerably less for the 220V 3-phase seen on most shop-sized equipment.

To maximize your chances for success using a VFD on an old 3-phase motor keep the lines from the VFD to the motor short. Transmission line effects are worse with long lines. Run single-phase out to the VFD, mount it on the machine close to the motor. Do NOT mount the VFD on a wall and run 3-phase out to the tool. As was already mentioned here, run a direct connection from VFD to motor, no switches, no fusing, no motor starters between the VFD and motor (unless specifically told to do so in the VFD manual – follow the manufacturer instructions!). The VFD usually provides all the protection needed and you risk destroying the VFD putting any of this between the VFD and motor.

-- "Find out what you cannot do and then go do it!"

Dont believe the crap Topamax is shoveling. I know of many guys who are running old motors on VFD with failure rates of less than 1%.

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

Do you have a master electrician lic? How many years experience doing trouble shooting and installation of industrial motors and controls do you have? Anyone ever write a letter of recommendation saying you set the standard in the industry? How many companies have incorporated your standards in their specifications? I could go on and on, but why waste any more time on such an asinine imbecile?

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0

Top and Paleoelectronics, if I get what you’re saying, use a big single phase 220 motor to spin up a big 3phase
motor, then let it run on 220v, disconnect the pulley and belt, let it run on it’s own and use it for generating 3-phase for the saw or whatever? Brilliant; like using a donkey engine to start BIG diesel engines with a smaller one. Brilliant. Only problem I have is space to do all that. Even a new saw at this time is a stretch—even a bargain—so I will put it on the back burner for now, but I DO appreciate the information. I stand in awe of your knowledge and the willingness to share. That is the great thing about this site. Some info is weak or wrong, but dig deep enough and you can find true experts in nearly any field. Thanks, guys.

On a side note, Ken, I don’t think Topamax would ever tell you how to insert an IV or de-fribrilate a arrythmic heart, or pull someone from a mangled car and do the least damage to the patient possible. Your little interjection was way off base, uncalled for, and outside the spirit of helpfulness of this site. It did no good, caused hurt feelings for no reason than to boost your ego, apparently. I think you owe him an apology.

Steve

PS Have a SAFE and happy new year, guys and gals

-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

Under that “I know a guy” logic maybe we should just abandon the National Electrical Code. I have seen a lot of wiring that bordered on arson but had not burned the building down yet; therefore, safety regulations must be over kill, eh?

Steve, You put single phase power on a 3 phase motor, give it a spin in either direction and it should run without load. Connect another 3 phase motor to the first and it will drive a machine. Not very efficient, but it will run.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Wake Up America!! Please read; http://www.commondreams.org/view/2009/01/26-0