Smart Guy question! - Electrical related (3 phase)...(let's see how good you are!)

Got a major fault alarm notification on a 200 kVA UPS going crazy, in a major data center. All sorts of alarms going off. Panels over-temp, things over amp...nothing makes sense.

Okay...some background. For whatever reason this is a 208V 3p input UPS, stepped down from a 277/480 V 3p 75 kVA transformer. In the middle we have an Automatic Transfer Switch and a twin 600kW generator setup. Okay, solid set up. Input voltage to the rectifier is 208 VAC 3p, to the batteries.

Something is going "BAD" wrong! Lugs in the service panel are getting hot (200+ degrees F). UPS is showing faults galore.

We get called. Crazy voltages on the neutral. Okay, let's start the checkout and see if you can figure it out....

Here's what we find. I go in and check the rectifier voltages and get the following (yes, I know it's crazy).

A-Ground = 208
B-Ground = 208
C-Ground = 208

All good, right?

A-B = 480
B-C = 480
AND...
A-C = 208 !!!

What happened?

This was measured on the output side of the maintenance bypass transformer!

Temps are going up in the panels. Something is going haywire. Shutting down the bypass and the distribution transformers means the data center goes dark (not an option!). Time pressure is ON!

What is the problem??

okay, for anyone trying to solve this, it's okay to just ignore 208 and go straight to 277. There are two transformers involved, but the 208 voltage is insignificant in the troubleshooting process.

Note: We (I) did figure it out, but the solution was almost unimaginable, but it was the ONLY possible answer without defying the laws of physics!

a reply to: Flyingclaydisk

Um I’m no electrician. Wait I am I guess . How do you have 208 on A and b and get 480 ?
Shouldn’t you need 277 v hots to get 480 between them ?

Messages we were getting was the inverter was about ready to blow, and the battery stack was getting hot.

Total time pressure!

What's the solution?

(Narcoleptic Buddah, Munnin...you have the answers, right? I'm a liar, fiction writer, right...what's the gawd dammed solution, smart guys???) How would I know this, if I didn't live it every day??? So, what is the solution...smart guys????

I'll take a stab...
Bad ground on one of the three phase legs.

It's always a bad ground... Although in colo gear those are often properly bolted in.

a reply to: Flyingclaydisk

Gotta love the angry pixies...
My guess is a ground problem.


On a side note...
208 is a pain in the butt.
I had a table saw that was 240 in a building with three phase power. I needed to add a $200 transformer to boost the power to 230 so the saw didn't just hum.

a reply to: Flyingclaydisk

Got a major fault alarm notification on a 200 kVA UPS going crazy, in a major data center.

Sorry bloke, can't help you with the electrical problem other than so suggest finding out who's major data center it is ....... if it's facebook, google or something like that ...... just let it burn.

Oh no actually I do have some advice ......... DO NOT, I repeat, DO NOT pour water on it to cool it down.

a reply to: Flyingclaydisk

Stop. 208 is not three phase, it's single phase double hot leg.

If you have 3 hot legs for 208 your electrician didn't do right.

I would be thinking the batteries, if lead-acid, had become dry, causing plates to collapse, short, this then causing damage to the rectifiers Its been a while since I delt with 3 phase but that's my excuse only if I am wrong

a reply to: myselfaswell

Urine works in a pinch!

As for the table saw... If it's just humming the starter capacitor isn't rated for what you're feeding it. You can kick start the motor by hand but I can see why you wouldn't want to on a table saw

a reply to: Flyingclaydisk
Going by your phase to phase voltage, it sounds like an open leg.
I am not an electrician .

originally posted by: Flyingclaydisk

(Narcoleptic Buddah, Munnin...you have the answers, right? I'm a liar, fiction writer, right...what's the gawd dammed solution, smart guys???) How would I know this, if I didn't live it every day??? So, what is the solution...smart guys????

So much drama! You care too much what randos on the internet think of you. I really don't care about your BS spam-posting. I ain't buying it and never will, so cry all you want.

Big, tough cowboy engineer turns into a baby when internet randos don't give you
e-validation.


🤡

originally posted by: Bluntone22
a reply to: Flyingclaydisk

Gotta love the angry pixies...
My guess is a ground problem.


On a side note...
208 is a pain in the butt.
I had a table saw that was 240 in a building with three phase power. I needed to add a $200 transformer to boost the power to 230 so the saw didn't just hum.

Wouldn't it have been cheaper to change the motor out to one that was rated 200-208 volts?

Software update.
Saw one time when the ambient temp in a data center was reading 600 degrees C
Most equipment now will shut down on an overvolt

a reply to: Flyingclaydisk

Ooooohhm...

Be one with the current jelly.

Edit: don't ask me... I'm still kicking the tires to ensure the windshield washer makes my headlights work🤗

Edit: I'm going to kick back and learn another lesson via ATS. 😙

Sounds like the 480 transformer has either a bad winding or loose lug. The transformer should also be k rated. A K-Factor rated transformer is one which is used to deal with harmonic generating loads.

a reply to: Flyingclaydisk

Open circuit on primary on transformer on C, with a short primary to secondary, perhaps?

I dunno, it's a good one.

originally posted by: butcherguy

originally posted by: Bluntone22
a reply to: Flyingclaydisk

Gotta love the angry pixies...
My guess is a ground problem.


On a side note...
208 is a pain in the butt.
I had a table saw that was 240 in a building with three phase power. I needed to add a $200 transformer to boost the power to 230 so the saw didn't just hum.

Wouldn't it have been cheaper to change the motor out to one that was rated 200-208 volts?

About the same price.
Depends on the motor.
A good one will cost more and the was a 5hp motor.

originally posted by: randomtangentsrme
a reply to: Flyingclaydisk

Stop. 208 is not three phase, it's single phase double hot leg.

If you have 3 hot legs for 208 your electrician didn't do right.

208 is normal for 3 phase.