Running Different Cross Section Busbars For Phase

There could be unequal distribution of currents in these bus bars and the associated effects.

Can you please detail what are all those effects can be...?

Different temperature rise, different thermal expansions, different forces, etc.

At the ACB terminals standard practice is to exactly match the bus bar width to that of the terminals width.

(a) There is not enough clearance to accomodate a larger width bus bar at the ACB terminals.

(b) A smaller width bus bar will be a source of heating at the point of contact with the breaker terminals.

Thickness of the bus bars only can be increased or decreased to cater required current.

Similarly, Please be aware that power supply cable wires with defferent line length will create phase imbalance and wire overheating.

prems4573,

The brief answers from electricalexpert65 are, in my opinion, correct. I am assuming that this is an AC application. I have been thinking about this before continuing--the only way to verify the suitability of this arrangement would be to do tests with an actual layout of the unequal bus bars. Certainly this would be required to pass short circuit withstand qualifications. Good luck.

--JMM

Theoretically, you can design such a bus bar system, but practically it will be difficult needing extra engineering effort in terms of travel and termination of such a bus bar system through a given switchgear. Moreover, both sizes (particularly the smaller size) must meet short circuit withsatnd capability criteria.

BB Raina