Does Current Limiting MCCB Tripping Cause Overvoltage / Voltage Spikes?

The construction of the MCCB in general and its Arc chamber in particular minimises the voltage spikes, generally. Please download and read ect163 of Schneider Electric.

Current Limiting MCCBs operate on the principle of Repulsion Force (due to the contact arrangement in such MCCBs) and this repulsion force is maximum at current peaks. If the loads are reactive (as in your case), then the voltage would be near zero during such current peaks and hence no transient voltage spikes.

As regards resistive loads, may be KVS can throw some light.

All i know is that breaking a resistive current is much simpler than breaking an inductive or capacitive current....the theory of the surge voltage calculation is beyond me

There are some formulae in ECT163, hope they will be of some help...

i have only tested per IEC, which is 0.35 pf, so, i have no experience on resistive loads...

Depends on level of voltage. Under 1 kV, it doesn't matter, because every devices (correctly build) include a filtering up to 2.5 kV (sometimes 4 kV).

Above 1000 V, it's different: Transient pikes arrive and may destroy filters. But you say 'in long length of cable feeder', so in that case, this cable feeder acts as a damper (depends on what you believe to be a long length!). In that case, cable feeder represents a capacity which transforms the Kapp triangle and smothes your transient pike. But this is true from approximately 75 sqmm and 300 meters of cable length. Under, you must add an overvoltage protection, behind or in parallel with your mcb, set to 1.5 time your voltage, or a serial overcurrent set to 6.5 times your running current (because your mcb trips about 7 times your running motor current, normally).

I hope this to be useful for you, BRZK

Dear All,

Thank you very much for your valuable comments.