voltage drop

[dshelley]

our site is running a plant at 1800 amps on a 2000 amp circuit breaker
the power company left the 1200 amp 480 volt transformer in place
now we are dealing with under voltages on our freq. drives
down to 435 volts isthat because of the small transformer?:grin:

 

[cpal]

What is the kVA rating of the transformer

 

[dshelley]

dshelley

dshelley

it is a 1000kva transformer

 

[drbond24]

That transformer is overloaded pretty bad. You're going to burn it out faster working it like that.

Anyway, I'm not sure if the transformer could be causing that because I've never dealt with one that was overloaded that much. I think it is possible that if the core was fully saturated and you kept pushing then the voltage might dip, but that is speculation on my part.

What I can say is that if the transformer is the problem, EVERYTHING will be affected, not just drives. Is your whole building having this problem, or are you only having trouble with drives?

 

[dshelley]

What is the kVA rating of the transformer

1000 kva transformer

 

[bob]

Have you alerted the utility about the situation. They will need to replace the transformer. If you have not contacted them, you need to do it now.
You will have some voltage drop in the transformer and the overload will make it worse. I think this should be moved the the Engineering Section.

 

[dshelley]

Have you alerted the utility about the situation. They will need to replace the transformer. If you have not contacted them, you need to do it now.
You will have some voltage drop in the transformer and the overload will make it worse. I think this should be moved the the Engineering Section.

we have told the utility and they'er looking into it, that was 4 weeks ago.

 

[dshelley]

One other thing we are running a lot of motors

 

[iwire]

In my area the plant would own that transformer and be responsible for it's replacement.

Be that as it may if yours is utility owned you can probably make a formal complaint to your areas 'Utility Commission' or whatever govt. body oversees that power company. If your power company has to adhere to ANSI C84.1 Your 480 volt service should be between 456 - 504 volts, this is at the service point, not at the motors. The voltage at the motors should be no less then 418 volts per the ANSI standard, 460 volt motors could operate in this range but obviously your drives are not that tolerant.

See this link for more info. keeping in mind your power company may have different standards.

http://www.pge.com/includes/docs/pd...ergystatus/powerquality/voltage_tolerance.pdf

 

[iwire]

I found this handy table while searching.

 

[LarryFine]

Anyone have the heart to tell Henry that "low voltage" means intentionally? :wink: