I finally got my new milling machine reassembled and up and running. Problem is, after ~2 minutes, the motor is ~180 degrees with NO LOAD, and after turning off it will not restart (just hums) until it cools down a tad. Prior to that, it runs fine; Both speeds (1720/3430) as well as forward and reverse work fine prior.
The facts:
It has a 3HP made in China motor.
I’m running a 30 year old Rotorway phase converter which works just fine on all my other equipment, but is only rated for 2 HP.
After running 2 minutes and trying to turn it off and on, it popped the 20 amp 220v breaker on the supply to the phase converter.
The wiring from the 50 amp subpanel to the converter is a 10′ run, 10 gauge.
All wiring to and from the converter except for what came with the machine is 10 gauge. The machine came with a stranded 16 gauge cable.
The wires coming out of the converter are 12 gauge.
So anybody have any clues?
I’ve had really, really bad luck with made in China motors in the past. Could it be the under rated converter or a bad motor? …or did I wire it wrong, something else?
BTW, wires out from the 4 position switch (FWD, HIGH, LOW/ RVRS, HIGH ,LOW) to the motor are, red, blue, black. All I randomly connected to hot…yellow with green stripe to ground.
Thanks in advance,
Jon
Edit: Rotoway, should have said Arco Roto-Phase and brown wire from switch to outlet , not red.
Edited 9/13/2003 9:47:34 PM ET by WorkshopJon
Edited 9/14/2003 9:34:12 AM ET by WorkshopJon
Edited 9/14/2003 7:13:30 PM ET by WorkshopJon
Edited 9/14/2003 7:14:38 PM ET by WorkshopJon
Replies
1st guess is delta wired motor, overloaded phase converter, all the resulting triplett harmonics go to only heat the motor.
No milling machine or Chinese motors here but I've run all my machines on one converter or another for years. Is that Rotorway a rotary phase converter? I had a poor experience with a static converter, not unlike your problem.
As your machine started, I don't think it's the converter, assuming it's a rotary. I'd be checking voltages and current draw at the motor. You should have been drawing maybe 15 A with the two motors. Yes? Got an induction ammeter?
For a test I once used a 3 hp rotary converter to power all my shop simultaneously, 18 hp total. Not started simultaneously. And not really comparable to your situation as all the tools helped each other. But that 3 hp converter had no problem starting the 5 hp planer or 5 hp dust collector.
PAHS Designer/Builder- Bury it!
"1st guess is delta wired motor, overloaded phase converter, all the resulting triplett harmonics go to only heat the motor"
Junkhound,
That's why I'm asking, as I know virtually nothing on this subject, Only that my other two 3 phase machines (a 1 and a 2 HP) work fine.
Jon
"I don't think it's the converter, assuming it's a rotary."
Va Tom,
Yes it is a rotary. And I'm miffed.
Before I go out to the shop and start turning on the power again, I need some direction. Like I said, I runs fine for the first minute, but builds heat like it is under load, which it is not (motor spins freely.
Jon
Well, Junkhound's gonna have to fill you (and me) in on delta motors and triplett harmonics.
My simplistic approach is to take a peek at the motor label and compare voltage and current draw to what it's supposed to be. Since it's overheating it's presumably drawing too much. If the voltage is right, you've got a problem, not that you didn't already know that. You can do this in the first minute.
Then since you know the phase converter is working, there is pretty much one direction for the problem, the motor. Got a spare? I can generally stock up at auctions for around $5.
Somewhere here I have the wiring diagram for 3 hp rotary converter capacitors. Built one for a guy down the road- worked great for around $100. I don't bother with the capacitors, just kick start my 5 hp one.PAHS Designer/Builder- Bury it!
This assume one know the basics (e.g difference between delta and Y, etc), anything of more depth refer to textbooks.
If the other 2 motors are Y wound, they do not overheat from harmonics, so you never would have seen the problem before.
The non-linear characteristics of the silicon iron in the rotary converter core (static would be even worse for different reasons) give rise to 180 Hz, 300 Hz, and 540 Hz harmonics and others, but mostly the 180 Hz. If you draw out the sine waves and their phase realtionship for the 180 Hz and 540 Hz components, you will see that they are literally short circuited in a delta winding-thus just heat the winding, be it either motor or transformer.....
If your Chinese motor is Y wound, my guess does not apply to your situation.
PS> simplistic ??-- but assume the motor is wired to the same voltage as phase converter????
Good luck.
"The non-linear characteristics of the silicon iron in the rotary converter core (static would be even worse for different reasons) give rise to 180 Hz, 300 Hz, and 540 Hz harmonics and others, but mostly the 180 Hz. If you draw out the sine waves and their phase realtionship for the 180 Hz and 540 Hz components, you will see that they are literally short circuited in a delta winding-thus just heat the winding, be it either motor or transformer....."
JUNKHOUND,
I'm staring to think you may be onto something. Though the phase converter appears to be rated for delta (and wye), do you have any clues on how I might test it? It does have capacitors. Do they go bad over time? BTW and FWIW, motor does not have any (at least external, and I've never seen a motor with an internal one.
Jon
Edited 9/14/2003 7:29:36 PM ET by WorkshopJon
I notice that there is a ground wire in the motor that is not hooked up. Connect it to ground. For safety and just 'cuz it might make a difference. I doubt it , but who knows how the chinese think.
The drawing that is labeled 3 ph AC220V /440V 60Hz is not to your motor.
I'm having a hard time comparing the switch schematic with the switch picture. I see 9 terminals and ? terminals and the connections don't seem to be in the same order in both cases.
After looking at the switch schematic and the interior tag, I think that in order to get two speeds out of a 3ph motor, they run it as a wye for one speed and as a delta for the other. reversing a 3ph just requires reversing 2 of the 3 wires.
Did the wires from the switch to power come with the motor? I noticed a green/yellow wire runing down that conduit.
To check out junkhounds harmonic theory, switch to the different speed and see how it works.
SamT
Edited 9/14/2003 9:36:06 PM ET by SamT
"Did the wires from the switch to power come with the motor?"
Yes, the machine came completely wired sans plug. Guess they figured most would be hard wired anyway. Given the shear weight of the machine (@3500lbs., guess they figured few DIY's would buy such a thing, and most would be in aan industrial setting)
"I noticed a green/yellow wire running down that conduit."
Yes, and positively it's the ground.
"To check out junkhounds harmonic theory, switch to the different speed and see how it works."
Good idea, off to do that now.
Thanks for your thoughts and time,
Jon
"Well, Junkhound's gonna have to fill you (and me) in on delta motors and triplett harmonics."
.....From VA TOM"
JUNKHOUND,
Just realized, my other two 3 phase machines have motors that are relatively inaccessible. While I've been using them for years, could the phase converter be bad/improperly wired all along?
Jon
Edit:
"If your Chinese motor is Y wound, my guess does not apply to your situation."
How do I tell?
Edited 9/13/2003 11:59:22 PM ET by WorkshopJon
What all is on the label for the motor? I am not interested in class and frame size. But all of the data on the voltages and currents.
Also if you have a voltmeter measure the 3 phases.
Bill,
Hopefully these pics will help. It appears from the interior tag as though it can be wired delta or Y. Any thoughts on how it's wired now? Would I risk damaging anything by swapping everything over? Anyway to tell?
Jon
I have not really had much to do with 3phase so I am not going to give you any solid answers here.
But maybe trigger some other responses.
I can't tell from the picture for sure. Do you have 3 independant black wires that go to the "outside" and 3 independant red wires or are the read wires dasychained.
If they are dasychainged then it appears to Y wired.
It has been close to 40 years since I had my Electric Machinery class, but I am confused by the label and connections. I am thinking that there need to be more connection for two speed and the option for delta or y connections. But then there should be two different voltages given for delta and Y connections.
Also you said that there where red black and blue wires from the switch to the motor, but none of them appear to be blue at the motor juniction box.
"Also you said that there where red black and blue wires from the switch to the motor, but none of them appear to be blue at the motor juniction box."
Bill,
I double checked. Should have said brown, black, blue plus yellow with green stripe to ground.
FWIW. the motor is definitely delta wired. I'm thinking it is phase converter related. Oddly, it has a 150% (of 2HP) duty rating as well a being rated for both delta and wye. Just spinning under no load I would think shouldn't be all that taxing on it.
Jon
I agree with JunkHound.........
First of all,the converter is undersized. Being a Chinese motor,it is probably Delta wired which exacerbates the problem. Often,proper matching of a motor to a converter is difficult and results in current imbalances due to the harmonics JunkHound mentioned. Motors are inductive devices and inductors are frequency dependent resistors. I'm not a big fan of converters,especially static. Even a rotary such as yours may be satisfactory if properly matched,but the motor will never reach its maximum life or efficiency. I've aquired a few machines from businesses that were selling them for different reasons,and they have all been 3 phase. Unfortunately,I don't have 3 phase so I've coughed up the cash and bought 2 phase(240v) motors. In my opinion,that is the way to go. How about selling that converter and applying the money to a new motor.
I have used rotary converters for many years and I have had misc. problems off and on. One thing to remember is to not to use the converted leg to run the magnetic/starter controls. Another is to check to see that all 3 legs are balanced by measuring the 3 combinations in pairs of 2, not one at a time. Beyond that, I'm having brain fade to as other possible problems. The biggest problems have always been with "European" motors that run under 50/60 hrz cycles. Might want to start there. another is that baybe one of the capacitors in the motor(if it has one) or rotary converter has gone out
"BTW, wires out from the 4 position switch (FWD, HIGH, LOW/ RVRS, HIGH ,LOW) to the motor are, red, blue, black. All I randomly connected to hot...yellow with green stripe to ground."
If I remember correctly (it's been awhile) this connection isn't random.
____________________________________________________________
The wiring.jpg pic shows how you connected the 8 wires from the switch to the motor. Is that correct?
The interiortag.jpg pic appears to show you how to wire the three hot wire depending if you feed source is wye or delta type. you've got to look at the tags on your Rotoway to determine that.
It looks like, if you have a wye source, you want to jumper, 10ga, the #1 terminals on the left side of wiring.jpg and connect the 3 hot leads to the right hand terminals, #2's.
conversely, if you have a delta source connect the three hot leads to the left #2's terminals and leave the right hand term's open.
If the motor runs backwards in either case reverse any 2 of the hot leads.
The motor only has 3 terms you can use at once. 3 for wye or 3 for delta.
I don't have a clue where the switch is located in the circuit nor how to wire 6 leads to 3 connections.
Reading the outsidetag.jpg pic, I am not sure if the motor is 2 speed or if the tags gives different specs for wye and delta usage.
Maybe they sent you the wrong switch?
Didn't they give you any paperwork?
Got a schematic of the switch?
Be aware that I am very doubtful of the veracity of my advice, given the very little known about this motor. I really think that you should take it to an electrical shop where they can put a multimeter on it (at the counter) and quickly tell you the real facts.
Not an electrician
Samt
Edited 9/14/2003 5:32:00 PM ET by SamT
Sam,
To answer some of your questions.
"The wiring.jpg pic shows how you connected the 8 wires from the switch to the motor. Is that correct?"
I made no connections myself other than adding a plug. The machine and switch were pre-wired.
"The interiortag.jpg pic appears to show you how to wire the three hot wire depending if you feed source is wye or delta type. you've got to look at the tags on your Rotoway to determine that."
I went to the Roto-Phase website (my mistake, that's the converter I have, hadn't looked at the name in a while)
http://www.powerbankcanada.ca/QandA.htm
and they claim their units are both delta and wye compatible. I get the impress simoltaniously.
"Reading the outsidetag.jpg pic, I am not sure if the motor is 2 speed or if the tags gives different specs for wye and delta usage."
It is a 2 speed reversible motor tied to a 5 (center off) position switch.
"Didn't they give you any paperwork?
Got a schematic of the switch?"
Yes, see below.
Thanks again Sam, and anybody out there who can help.
Jon
First check the basics. Make sure the voltage into the converter is 240v, or there about, but don't get hung up with minor variations. If by chance it was hooked up on 120v I would think that this could easily be the, perhaps not the only, problem. Check output voltages while motor is under load. Again anything close is OK. If this is a solid state converter don't be too concerned if two legs are a bit, just a bit shy.
I'm a little concerned about the converter being rated for only 2HP while the motor is 3HP. This could easily explain the problem in and of itself. You could have insufficient capacitor capacity to make up the voltage on the synthesized legs. A larger converter would correct this problem. Disregard this if the converter was working with the motor previously. I reread your post several times but it is still unclear in my mind wether or not the converter was running this motor at some earlier date.
This only really applies if this is a solid state converter. If this converter had previously run this motor I would suspect that one or more of the capacitors have dried out, shorted or otherwise failed. Not an uncommon problem for these types of capacitors. This could lead to the symptoms described. Replacing the defective capacitor/s should make this right. A little experimentation while monitoring Current among the leads with a ammeter will get you there. You want the loads to roughly balance. Don't try to go for a theoretical figure. Be sure to disconnect the power and discharge the capacitors before playing. Add more to the low leg/s. A weak leg, insufficient stack of capacitors, makes the others, typically the unsythesized one, to try to carry the load. This overloads the windings causing the motor to run hot and the circuit to trip.
From what I could gather, the photo of the exterior plate have glare obscuring some of the information, the motor seems to be a common two speed model. The two configurations, delta and wye, only change motor RPMs and effecting the load only slightly so it is pretty much the same either way for the converter. Three hots and a ground. The placement of these is immaterial if the internal jumpers, or connections are made correctly. Worse case is the motor spin opposite the controllers direction. A problem easily corrected by switch any two leads.
Harmonics are a possibility but much more common with multiple loads on one converter especially if one is a switching power supply or a phase corrected motor package. Mostly, the few times I have seen true harmonics problems, it was on separate single phase loads on a shared neutral. Offices with many switching power supplies are the most common place to see this. Many harmonic problems come down to a few loose connections, common sense relocation of loads and basic system design. Dedicated circuits, with a separate neutral, for electronics is a good idea that has gained acceptance with many designers.
"You could have insufficient capacitor capacity to make up the voltage on the synthesized legs."..."A weak leg, insufficient stack of capacitors, makes the others, typically the unsythesized one, to try to carry the load. This overloads the windings causing the motor to run hot and the circuit to trip."
4Lorn1,
I replaced the capacitors in the phase converter and everything appears to be working properly. I ran it for an hour under a moderate load (4800 spindle RPM) and the motor temp was about 100 degrees and it took awhile to get there.
Interestingly, phase converter may be older than I thought. Quite possibly as old as 1957. The date code says 1578 and I know for a fact that it was in service in 1974. The person I got it from is dead, so I can't ask him. Saw they (Arco, mfr. of Roto-Phase converters) still make similar models.
Thanks 4Lorn1, and to all for your advise and input.
Jon
Edited 9/16/2003 6:34:19 PM ET by WorkshopJon
Edited 9/16/2003 6:35:21 PM ET by WorkshopJon
Glad to hear everything worked out for you. One day, might be on the other side of the rainbow, I hope to set up a couple of small machine tools as part of a shop. I always think three phase works so much more smoothly on these beasts. You can run them on single phase but they always seem to run rough and lack authority.
It is not uncommon for those capacitors to dry out and change value in time, especially if it was from the 50s. You might also find that it will pay to check the balance every so often as they get warmed up a few times and run in.
Please do me a favor and take those old capacitors to a proper waste disposal company. If they are old, prior to the mid 70s, they likely contain PCBs. Doesn't take much of that stuff to slowly poison a good patch of land and anybody or anything that lives, it bio-accumulates. Once released it is hard to get out of the environment so please play nice.
"Please do me a favor and take those old capacitors to a proper waste disposal company. If they are old, prior to the mid 70s, they likely contain PCBs."
4Lorn1,
Thanks again for the advice, I pulled them out of the trash. The county I live in has an "amnesty day" for toxic waste once a year. I'll turn them in then
Jon