Hiya,
I have a question in regards to an ATS with a withstand rating of 65kA spc / 50kA (0.05sec).
My understanding is that in order to utilize the 65kA rating, specific breakers are required by the manufacture.
In the scenario i'm looking at, it would fall under the 50kA for 3 cycles.
I'm having trouble understanding the limitation of this characteristic.
Let's say based on a power study short circuit analysis, the maximum available fault experienced on the ATS bus is 13kA (1/2 cycle, symm. fault).
The breaker feeding the ATS upstream is an LSI MCCB that has an override inst. trip at 14.4kA.
My question is, do i need to still set the adjustable inst. of my MCCB to to interrupt the fault at 13kA? I know that the ATS is tested to withstand 50kA for 3 cycles, but without an inst. set to the max of 12kA, it would take about 10 cycles for the fault to clear on my short time trip based on coordination requirement.
I have a feeling it's probably not an issue and the ATS could handle the duration of 13kA for 10 cycles based on a simple i2t calculation, but is that enough justification or is this something the manufacture would need to provide (equipment damage curve)?
I've really only seen equipment with a flat kA number on it, and if the max available fault simulated on the bus is less than that max withstand on the nameplate, it would be acceptable for install. is that not correct?
Thank you!
I have a question in regards to an ATS with a withstand rating of 65kA spc / 50kA (0.05sec).
My understanding is that in order to utilize the 65kA rating, specific breakers are required by the manufacture.
In the scenario i'm looking at, it would fall under the 50kA for 3 cycles.
I'm having trouble understanding the limitation of this characteristic.
Let's say based on a power study short circuit analysis, the maximum available fault experienced on the ATS bus is 13kA (1/2 cycle, symm. fault).
The breaker feeding the ATS upstream is an LSI MCCB that has an override inst. trip at 14.4kA.
My question is, do i need to still set the adjustable inst. of my MCCB to to interrupt the fault at 13kA? I know that the ATS is tested to withstand 50kA for 3 cycles, but without an inst. set to the max of 12kA, it would take about 10 cycles for the fault to clear on my short time trip based on coordination requirement.
I have a feeling it's probably not an issue and the ATS could handle the duration of 13kA for 10 cycles based on a simple i2t calculation, but is that enough justification or is this something the manufacture would need to provide (equipment damage curve)?
I've really only seen equipment with a flat kA number on it, and if the max available fault simulated on the bus is less than that max withstand on the nameplate, it would be acceptable for install. is that not correct?
Thank you!