Big Problems Need Help GX7 Atlas Copco 240/480v Screw Compressor MULTITAP Issues 1

[TurboService]

Hello,

Im in a pickle and wondering if anyone can help me out. I run a small machine shop here in NJ and the facility has 480v but each unit has a step down transformed (single phase 240).

Anyway, my electrician came in yesterday and installed the 3rd phase into my suite. All of the work was complete and we decided it was time to connect the GX7 Screw compressor. Everything seemed striaght forward, the multi-tap Siemens 160/489VA 4AM3841-8BD40-0CN2 has all of the jumper pins clearly marked on the front.

Little background, my electrician made it clear from the beginning that this unit was originally wired 480v from the factory. Then it was set up to run 240v 3phase at the location I purchased it from. Oh yes it was tested and running when I bought it on the 240v 3phase.

The electrician pinned out the Siemens multitap until he felt it was correct and then explained his work to me. I agreed with him that it looked to be correct so we fired up the compressor and all I saw was a big flash and an explosion. The electrician made it clear from the beginning that this could happen but even he didnt expect this to hsppen.

Does anyone have a clue why this would happen and what the possible culprit could be?
Would this explosion be limited to the multitap or should I be looking for other replacement parts as well?

Is there a lower price alternate to the Siemens 160/489VA 4AM3841-8BD40-0CN2? If so where can I find it?

Thanks for the help, this one is going to leave me flat broke!

Thanks,
Sean

 

[wayne440]

Does anyone have a clue why this would happen and what the possible culprit could be?

Your "electrician" is probably incompetent. His forecast of the failure and asking you to agree with the configuration are classic precursors to disaster and subsequent blame shifting.

Would this explosion be limited to the multitap or should I be looking for other replacement parts as well?

You need a qualified and experienced person on site to determine this.

Is there a lower price alternate to the Siemens 160/489VA 4AM3841-8BD40-0CN2? If so where can I find it

I think that is a control transformer. It should cost well under $100. If you are really broke and willing to take another chance, Ebay has a couple right now.

 

[waross]

A lot of information missing here.
I assume that the explosion was the control transformer letting out the smoke. Please confirm.
What voltages do you have at the disconnect switch? Both voltage to ground and voltage phase to phase.
What voltage was applied to the transformer?
What voltage was the transformer tap set for?
That transformer looks like a 115/230 volt secondary.
Lots of generic replacements available.
A couple of suggestions.
1> One phase of 480 Volts was brought in but not transformed down to 240 Volts.
2> Your electrician inadvertently misconnected the secondary. If X1 and X2 or x2 and X4 are inadvertently swapped, the transformer will explode. It may even blow small pieces of wire out of the winding.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[TurboService]

Bill,

Your help is appreciated, I sent and email to the electrician hopefully he will reply soon.

As for the 240/480v situation, this compressor was purchased "used" 6 months ago from a site where it was wired and working on 3 phase 240v from what the owner states. We reviewed the compressor "ID- plate" and the electrical diagram "print" both reflect the compressor has been altered from its original state 480v and the multi-tap was changed for the 240v. My shop is now wired for 480v and the electrician was aware of the 240/480 situation and made the changes to the best of his knowledge and we know what happened after that!

I took the Siemens 4AM3841 multitap out of the compressor and the wire winding plastic cover looks opaque and dirty. Both of the main terminals 1 & 2 have a black charcoal finish like an explosion happened.

Any ideas where I can buy a generic unit to replace this one or a company that will sell this alternate and cross reference it for me?

 

[jraef]

The only facts we know are:

A) The electrician you hired sounds like someone without adequate INDUSTRIAL experience. Unfortunately people ASSume that an "electrician" is someone who can handle any kind of electrical installation. But here in the US, there is no licensing difference between the guy who connects light switches in outhouses to the one who makes up motor connections in rock crushing plants. In other words you can easily get the WRONG person for the task if you just believe the exaggerations they print in their phone book ad.

B) You seem bent on describing what it WAS connected for when last you saw it work. That's understandable, but no longer germane. What is important is what is it hooked up for NOW? 480V or 240V? And what are you feeding it with? 480V or 240V? Do not assume these are the same, given the assumed incompetence of your electrician.

C) That transformer is ONLY for the control circuit that operates the motor CONTROLLER, which has nothing to do with the motor wiring itself. So if it was originally running on 240V, and you fed the controller with 240V 3 phase (see B above), then nothing in the CPT (Control Power Transformer) should have needed to be changed. If you changed to 480V feed for the motor, then that transformer would have needed to be re-connected (again, see B above), but only on the PRIMARY (High Voltage) side, and only one wire needed to be moved. If your nincompoop electrician moved more than one wire, there is no way of telling what he did.

D) The likelihood that there is not collateral damage to the control circuit components for the compressor is very high. A misconnected CPT could have easily pumped too high of a voltage into the devices below it, which may have damaged them beyond repair.

You need to get that email from your electrician and then fire him. Find a QUALIFIED electrician that works on INDUSTRIAL equipment and have him come out to evaluate the whole controller and motor connection situation. Better yet, call an ATLAS COMPRESSOR service tech out to go over it. They are not necessarily electricians, but they will know that control system inside and out.

By the way, ANY CPT rated for 100VA and 480X240 to 120V will replace that Siemens transformer, they are VERY COMMON at any INDUSTRIAL electrical wholesale house. The only thing special about that transformer was that the OEM who built the system probably wanted to be able to send it anywhere in the world, so they wanted the multitude of available voltage taps. You no longer need that.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[TurboService]

Gents,

This is what he replied with, I hope this will help. All of you have been helpful thank you very much.
Sean

Electician:
"id like to call the manufacturer and ask when rewiring what is the transformer configuration..I agree below Its probably 120 control wiring The voltage on the disconnect switch is 480 and 277 to ground . I didnt change x1 2 3 or 4 I change what I believed was what i read on the transformer to convert to 480v . Ill work on this monday lets keep in touch .thanks Jim"

Thanks again.

 

[waross]

The other possibility is poor workmanship. If the transformer was connected with stranded wire, one strand may have bridged across to another terminal. This will give you all the symptoms you describe and, after cleaning, there may be nothing wrong.

Bill
--------------------
"Why not the best?"
Jimmy Carter