UPS Output CB sizing
UPS Output CB sizing
(OP)
Hello everybody
First of all please excuse my english.
We are installing a MGE Galaxy 5000 UPS rated 100KVA.
In the installation manual they recommand & 250A breaker in the input which i think is normal. But in the output they recommand a 120 A breaker. Is this breaker undersized ? or i'm the one who's missing something ?
I'm always working with the formule : Amps = KVAs x 1.55 so the output current would be normally 155 A.
Thank you in advance.
Amar OUZOU
First of all please excuse my english.
We are installing a MGE Galaxy 5000 UPS rated 100KVA.
In the installation manual they recommand & 250A breaker in the input which i think is normal. But in the output they recommand a 120 A breaker. Is this breaker undersized ? or i'm the one who's missing something ?
I'm always working with the formule : Amps = KVAs x 1.55 so the output current would be normally 155 A.
Thank you in advance.
Amar OUZOU






RE: UPS Output CB sizing
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: UPS Output CB sizing
No idea where you got that formula but it would only apply for a certain voltage and also for certain applications.
RE: UPS Output CB sizing
RE: UPS Output CB sizing
The unit has an input/output voltage of 3 phase 380V.
@LionelHutz: The formula has a little error in it; it's AMPs = KVAs x 1.52 and it applies only for 3phase 380V.
S = sqrt(3)*U*I so I = S/(sqrt(3)*U)) this is where I calculated the formula and it' easy to keep in mind.
Thank you to all again.
RE: UPS Output CB sizing
Did you ask them why they recommended that size? Possibly, they gave that size based on a higher voltage, such as 480V or 600V.