Dubledox
Member
- Location
- Iowa City, Iowa
Greetings, all. Does anyone know why a thermal-magnetic tripping unit (an Eaton KT3400T hooked up to an Eaton HFD 3400F MCCB), would have three adjustable settings? I always thought they generally had one setting for instantaneous tripping, which is often 5-10 x I_n. My thinking is this is because there are three phases, so there is one instantaneous setting per phase. But I can't see why this would be.
If you are interested in more details, here is the system: A three-phase, 480V panel is being fed from a low voltage switchgear bus. The main breaker is a 400 A (I_n = 400 A) molded case circuit breaker. The panel feeds a couple of control panels and a few VFD's for pumps. Currently, the settings are maxed out at 10x In (4000 amps). I calculated the minimum sized fault on the panel to be just over 8 kA, so in addition I do not even see how adjusting these settings can realistically affect my system.
If you are interested in more details, here is the system: A three-phase, 480V panel is being fed from a low voltage switchgear bus. The main breaker is a 400 A (I_n = 400 A) molded case circuit breaker. The panel feeds a couple of control panels and a few VFD's for pumps. Currently, the settings are maxed out at 10x In (4000 amps). I calculated the minimum sized fault on the panel to be just over 8 kA, so in addition I do not even see how adjusting these settings can realistically affect my system.