Bus Duct Design

If you have a consultant to design something and to advice you, always seek him for any clarification. He has vast experience in the particular field than we have.

Normally, BUS system reduces the area for installation; for 1750/4500 Amp, just think about the number of cables that need to be spread over between the switchgear and the motor. The motor terminal box does not have such big space to accept the termination of such large number of cables.

Yes.

yes, bus duct is the way.

How many XLPE cables would you consider for the load? Personally I'd be looking at 3 X 500mm² per phase, not an easy task to make off in to a terminal box. I've done it, it wasn't fun.

What are your reasons for disagreeing with the consultant?

Out of interest, what are you doing that needs motors of that size?

What is the machine driven by this motor,how much is the length of duct required & how much voltage drop is allowed during starting & running.

What the Consultant's advice appears to be more appropriate considering the convenience, the large load current involved and economy of the proposal.

IMO, if the generator is provided with NEMA MG1 [See Fig.20-3] Type II Machine Terminal Housing Standoff-Insulator -Supported Insulated or Uninsulated Termination, 2 cables of 750 MCM 11 kV may be suitable [According to NEC Table 310.60(C)(69) Ampacity of each cable is 885 A in air at 40dgr.C installed in ventilated cable tray keeping one cable diameter clearance art.392.17(B)(2)(b) .

These cable temperature will not be more than 90 dgr.C -if the initial temperature is 40 dgr.C-that means" from no-load" at 4500 A within 20 sec.