chenley

I currently have an industrial client that has purchased a used piece of equipment without talking to anybody about it. He ends up calling us to come in and hook the juice to it. When I got there I inspected the nameplates of the three motors on it. It turns out two of the motors are German made (220/380) and one is a Baldor (230/460 VAC). I ask him where he bought the used equipment and he told me that it was running in South Carolina, looking at the phase tape it was hooked up to 240 3-phase.

This client only has 480 3-phase, my question is this: If I hook these two German motors to 480 when they are only rated at 380 what will happen? I'm guessing it that they will run for about 1-2 hours before finally just burning the windings out and or catching on fire.

I have been looking at a step-down transformer which the list price on SQD is ~$9,000. Also have been looking in the used motor market which the largest motor is 40HP which can be purchased for about ~$1,900. I'm just trying to get a few more points for my arguments. I really don't want to go in and say that I have no real idea what will happen if I hook these motors up to 480, that they will just burn up.

Anyone ever tried this, I'm actually kind of interested in what would happen. I've seen a 50VA transformer tapped for 240 and hooked up to 480 which made a nice buzzing sound and finally a small explosion. I'm thinking that hooking these motors to 480 something along those lines would happen also.

Thank you for your time.

chenley

Also these German motors ARE rated for 60HZ, not 50.

Kletis

Sounds like a strange couple of motors. I would think that you would be running at about 125% of rated voltage and that is way too much. I would not hook up these motors at this voltage.

If he insistst you should definitely do it though. Film it and let us know what happens. This could be a great learning exercise for all of us. Sounds like he is too "smart" for his own good...

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Kletis...

Billy_Bob

What happens if the motors rotate faster? Any safety issue with the equipment they are connected to? If for some production line thing, those workers might be working quite fast!

In any case I would write this all out in a letter stating that you advise against doing this, that he is doing this at his own risk, etc. That they could burn out or cause a fire. Then make him sign it.

John

Torque = ((voltage x amps x efficiency)/ 746)*(5252/rpm)

If you use this formula you will find that using 480 V as to using 380V to power the motors will just increase to motor torque. Running a 380-volt motor at 480-volt most likely will not burn the motors up. I have done this a couple times and the motor ran just fine. It will depend on the condition of the 380 volt motors and what they are driving. You may have to change some of the motor controls (fuses, starter overloads, starters and coils, circuit breakers, etc) when you decide what to do.
It’s an onsite call as to what to do and assume that whoever worked on the machine before you got there ….did it WRONG.

Also look into a buck transformer for the two motors.

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Doubt All Before Believing Anything.......

chenley

Here's a picture of the control panel to answer a few questions regarding the application:


This is for a grinder system. Pretty much all the scrap wood leftover will be run on a conveyor system to the rear of the building where this machine sits. The 40HP motor runs the main grinder, the parts in the control panel measures current draw and will reverse the motor for about a second and throw it forward again. The other motor is only 1/2hp which runs the hydraulics, that motor I WILL make them replace since that part of the equipment would not be easily replaceable.

The control wiring is 24VDC and 240AC both coming through the control transformer, which I would have to retap to 480VAC. I do have full prints, a list of components and functions for all the material in the control panel which is a first .

Kletis: I will definitely film the outcome if they give me the go ahead to run it in this fashion. They probably will, they'll have to buy a used motor either way and it would be difficult for them to sell this motor in the American market.

Billy_Bob: Yeah, their will be some signatures from the owner, office manager and shop foreman. This equipment is outside and out of harms way so I would probably be the only one in any real danger.

John: Thank you for the formula hadn't used that one in a couple of years. I'll run through the math tonight so I will have more information to present to them.

Mainly in the control panel I will have to dial the amperages, replace the overload in the top left of the panel, and about three breakers the protect the motors which are rated at the 240VAC amperage. Still looking for other things within the panel that I might need to changeout. Still going over the plans to make sure I didn't miss anything.

chenley

Also if anyone wants to see the prints and components to this equipment. I transferred everything to an AutoCAD file and an Excel file. Just shoot me your e-mail in a PM. I gotta say it is a pretty damn nice setup.

Billy_Bob

Boy I looked at all the stuff in that control panel - relays, transformer, etc. and thought "Oh no... Too much voltage and they might not last very long..."

Then I read this...
[The control wiring is 24VDC and 240AC both coming through the control transformer, which I would have to retap to 480VAC.]

...and thought ok, no problem!

brian john

Get a buck boost transformer and buck the voltage as low as possible. Over voltage will at some point be detrimental to the motors. You can double buck boost and you should be able to drop voltage to 400 VAC. OR you can go to isolation transformers and lower the voltage with double transformation and setting the taps accordingly. Lastly and not sure how this would fly with listing, you could use a isolation transformer 480 120/240 as a buck boost change taps and get to 380 (or close). The kva of the transformer would be based on the amount of voltage lowered by amperage and you would need 3 transformers.

Kletis

Good idea!! You would definitely be better off running the motors as close to the rated voltage as possible. I think that by running too much voltage you would have a much shorter life span on the motors.

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Kletis...

micromind

These are almost certainly 6 lead motors, low voltage connection is L1=1,6 L2=2,4 L3=3,5 and high voltage connection is L1=1 L2=2 L3=3 4,5,6 tied together.

If so, they'll work fine on a 240 system, but connecting them to a 480 volt system would likely result in core saturation, along with the accompanying heat and noise. They'd likely work for a while, but not all that long.

How about the control transformer? Is it 220/380 as well? Blasting it with 480 will result in an increased output voltage. Some of the controls might not like it very much.

As stated above, buck-boost transformers would be the way to go. If you bucked 48 volts off, you'd be left with 432. A bit high, but likely OK. I'd keep these as small as possible, to minimize the effects of 'plug reversing'. That's plenty hard on any motor, and much worse on one that's run overvoltage.

Rob

chenley

They're WYE start DELTA run motors, has the U1, V1, W1, U2, V2, W2. Kind of surprised me when I opened up the peckerhead and only saw 6 bolts.

chenley

Thought about using a transformer, except the smallest transformer that would work will need to be 50kVA if I calculated that right for 240VAC. Looking at the prices it seems that replacing the motor with a used one (would be hard to find) would be the best option.

I do love all the ideas though, will just need to do a cost analysis on it and figure out what would be best for them price-wise. Been a long day, was suppose to be out there, except an emergency call came in about a downed service pole, so I've been playing in the dirt all day, after my hammer drill broke halfway through my first ground rod .

micromind

If a 6 lead motor is wye start/delta run, then it is single voltage. A dual voltage 6 lead motor can be started on wye and run on delta at low voltage only.

Looking at the picture, it looks a lot like the 2 top contactors are reversing, and the bottom 3 are indeed a wye/delta. I'd be a bit nervous though, there are no mechanical interlocks. If the middle and far right contactors are ever closed at the same time, it'll blow up. This could very easily happen if the start timer failed and was replaced with a standard timing relay. A wye/delta timer always has a short (1/2 second or so) delay during the start/run transition. Scary.

The reversing contactors are not mechanically interlocked either. If both were closed at the same time, a similar explosion would occur. Equally scary.

I'd like to see the drawing of how they wye/delta start a 6 lead dual voltage motor on high voltage. I could easily be wrong, but I don't think it can be done. If the motor has 12 leads, then it's easy.

Rob

P.S. If you use buck-boost transformers with 48 volt secondaries, you'll need two 3KVA units to produce 62.5 amps. 5KVA ones will produce 104 amps.

Rob

P.P.S. If this is connected to a 240 volt system, there are two 3 pole terminal blocks on the bottom. All 6 motor wires land here. Check VERY carefully, most likely the left block has 1-2-3, and the right block has 6-4-5, in that exact order. It's hard to tell from the picture, but phase A must go to 1 and 6, B goes to 2 and 4, and C goes to 3 and 5.

Rob

martinre

I had to jump in on this one. I would go with a step down transformer, as far as the cost, it should not cost 9000 dollars for a step down transformer for this application. I am very familiar with the 380 volt motors and they will run very hot at 460 volts. A transformer should be around 2000 dollars or less. Try a different supplier.

brian john

50 KVA $1,200.-1,800.00

Buck boost assuming 50KVA at 380 VAC 75 amps X 48 VAC = 3.68 or a 5 using two sets you could drop voltage 96 volts.

John Valdes

I would not buy anything. First of all, I have never seen a 380 volt motor rated at 60 HZ. The standard will be 380/50Hz - 460/60 Hz. Double check your nameplate. Six lead motors do not come in two versions. They can be used as dual voltage and for wye/delta starting. Wye is high voltage and delta is low voltage. Six lead motors should not be used for dual voltage, but they are marketed as dual voltage. Some IEC motor manufacturers are addressing this issue by changing to 9 lead.

If it were me, I would connect the machine for 460 and wait for the motors in question to die on their own. Then you can replace them with 60 Hz motors. You may be very surprised at how long they may last. You personally may never replace them. So do not buy spares right away. Make sure you know where to get the replacement's when the time comes.
Make sure your customer understands what you plan to do. You are saving him some money up front.

brian john

We just received a job today requesting a 480/400 at 150 kva and 30 kva transformer for EU equipment. Engineer spec'd Square D and included part numbers.

John

I will second that.

Interesting problem so let me add some more variables to the conversation.
I found these wiring diagrams for a star-delta starter and a two speed motor. The wiring of the controls are almost identical. The motor nameplate data needs to be checked and double checked.

Also a new 3 phase 240 volt service may be an option. It worked before and it should work again this way.

Attachment 648

Attachment 649

Looks almost the same don't they....motors are 6 lead in both controls.

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Doubt All Before Believing Anything.......

micromind

The two types of controls are indeed very similar. If the motor is actually 2 speed and has 6 leads, it will be single voltage.

In looking at the picture as closely as I can, I believe this is a reversing wye start/delta run controller that can be operated at 220 volts only. It could be modified to operate on 380 volts, you'd need to by-pass the wye/delta start system, connect the motor for 380 volts, and start it across-the-lines. You'd also need only 3 wires between the starter and motor. The current set-up has all 6.

Rob