MCCB tripping reasons

What are the technical possibilities if one 800 A MCCB trips which feed ing supply to UPSs

Hi, The following are some reasons:

(1) As a previous cr4 member said >800amps will do it.

(2) A slack connection at the breaker lugs will heat up the lug. This heat will travel from the lug to the tripping mechanism and trips the breaker.

(3) Pitted points within the cb. These points can easily become pitted because of the high inductive loads this cb switches on and off. There are input transformers in each of the ups.The pitted points generate heat (I squared R losses) and this heat tripps the cb.

(4)Check for any load shedding device installed in the cb. The load shedding device will trip the cb lf you experience a brown out.

(5) Check for loss of air condition in the main cb room(if equipped). Closed off or partially closed off vents,acu needs servicing.

(6) Check for any civil works that was recently done that would inhibit the flow of air.Check the ambient air temperature.

(7) Check all bolts & lugs on both sides of the cb. Slack connections causes heat.

(8)cChech the temperature of the incoming bus,The heat from an incoming can trip the cb

(9)If your operating current is close to 800amps in any one or more phase, sudden load increases in any one ups can trip the main cb, whilst the sub breakers remain on.

Regards