Buss Bar feeds.

[deetz]

So they are looking to add more CNC machines to an existing 400 amp Buss Bar over the manufacturing floor. How do you determine how many machines can be on that 400 amp line?

 

[RedSnake]

One way is measuring the max current consumption on every machine connected, when driving them, then you you know what you have left.
We usually measure that and the total current consumption.
Then you need to determine how much of a chance you are willing to take that all machines wont go with max at the same time. ;-)

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[deetz]

I would be at about 700 amps. We have 6 Buss Lines, and all of them are overloaded, but have never had an issue. I installed meters on the 480v ones and never read above 300 amps typically. Just wasn't sure if there was a derating calculation for Multiples. I've conveyed my concerns on adding machines all the time, but usually it goes on deaf ears. I guess when the main trips and all the machines on that line crash, they may listen. Thanks for the quick reply. I appreciate that.

 

[deetz]

Sorry i misread that. I meant when I add up all the max amp loads on the labels.

 

[TugboatEng]

You could use a current transformer to interlock the start operation for all of the machines if the bus current is above a certain threshold.

 

[RedSnake]

I asked for a measurement like that not long ago.
What they measured was peak and average current over a period of time.
Total and for the separate parts.
They did it twice because the consumption was so low they thought it was something wrong with the instrument.

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[IRstuff]

We have 6 Buss Lines, and all of them are overloaded, but have never had an issue.

They never had cold temperature Shuttle launch problems until Challenger.
Yeah, and they never had a problem with icicles failing off the Shuttle, until Columbia

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[jraef]

Technically, the bus limit is 400A, so you would determine the full load amps of each machine connected and when you get to 400A, you are done.

Realistically, people use what's called a "diversity factor" relating to the actual LOAD on the machines and which of them will be operating at the same time. That is something that nobody can help you with, it has to be determined / observed in your specific installation. So having 700A worth of machinery connected to 400A bus may be acceptable in one place because someone KNEW that the Gachunketta machine was never going to operate at the same time as the Mawhozis machine, and all 14 of the Whizbangers are actually never more than 50% loaded at any one time, etc. etc. etc.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[EdStainless]

Our maintenance manager knew 2 things
1. 80% of the time our equipment drew a lot less than rated load.
2. If it was possible to overload a line someone would.
So he built a system where machines needed 'permission' to start. Once load on the bus reached a certain level nothing else would turn on. People complained, but they didn't burn out motors, cause whole sections of the plant to shut down, or damage the bus system.

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[deetz]

That's kind of what I figured. Thanks for all the help guys It's greatly appreciated.

 

[RedSnake]

guys ......

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[deetz]

I apologize.

 

[RedSnake]

It is okey ;-)

Best Regards Anna

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein