Bus Rating
Bus Rating
(OP)
Hi there. I have a question regarding bus rating. Does higher actual bus voltage mean current rating should be lowered? For example, if a 4160v bus is rated at 2000A, would that rating decrease if the XFMR feeding the bus is at a higher tap? In other words, should I worry about Amps or MVAs?





RE: Bus Rating
The bus also has a maximum voltage rating.
Changing transformer taps doesn't change the switchgear bus rating. But it does change the transformer rated amps.
David Castor
www.cvoes.com
RE: Bus Rating
RE: Bus Rating
Read what he said, don't read more into it than exactly what he said.
Bus has a current rating. So a 2000A bus is rated 2000A at 1V, or 480V, 0r 4160V
Voltage on the bus has only to do with the spacing and / or insulation rating, hence a maximum voltage rating as he said. That just means that if you have a bus system designed to be used in 4160V gear it will likely be 5kV rated bus, you cannot use it for 15kV gear. But you can use it at 3300V or 2400V or 1500V, anything lower.
That still has nothing to do with the current rating. It's still 2000A no matter what.
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RE: Bus Rating
RE: Bus Rating
RE: Bus Rating
RE: Bus Rating
RE: Bus Rating
Notice that at +2-3% the current drops ever so slightly, but at +10% it goes well above what it would have been at rated voltage. So for your 4160V motor, the motor nameplate voltage is likely 4000V (to allow for voltage drop), so at 4300V you would be in that range where it will be drawing more current.
"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: Eng-Tips.com Forum Policies
RE: Bus Rating