Multiple Feeds to a race track bus bar

Start-up Concerns:

Given the information you provided, I would check the bus arrangement during your start-up procedure to insure that the bus phasing remains the same from section to section such that the transition you spoke of would not cause a phase to phase short.

Design Concerns:

Because the collectors can connect two sections of the buss bar during a transition, I would think that the collector and any wiring in the dual collector path would be rated for the max current that any one section could provide.

If all your feeds are from the same MCC (though different buckets), the transition should only force a sharing of the load during that time.

Failure modes to consider:

• Fault occurs in traveling unit while in transition between two sections. The over current device for each section would have to operate to interrupt the fault.
• A unit enters a faulted section, or a section where a faulted unit is. The transition would cause fault level currents to travel through the collector system

Safety concern:

A section is locked and tagged out for some reason. A traveling unit is operated in an adjacent section into the transition, re-energizing the tagged-out locked-out section. This could be prevented by locking out adjacent sections.

... oh wow! the re-energizing of a "locked-out" section is a concern I had not thought of. Thanks for the thought, we'll have to take care of that somehow.

We have several cranes set up like this. We do not have any problems with the arrangement, in fact, it is a common arrangement for overhead cranes with very long runs or that need to have a maintenance area that you can tag out one crane while having another still run and not affect production. One thing that you will need is an isolation zone. With an isolation zone, you have the feed in the middle with bus ties in the area, ours are approximatley 20 ' long. The idea is that you can isolate the feed and the bus ties on either side of the rail and create a dead zone, that way if a crane accidentally runs into your isolation zone you do not reenergize the section that is locked out. The only problem at that point is letting your operators know where the isolation zones are so they don't run into it. It's a pretty scary site to see a 20 ton crane hit an isolation zone at full speed and suddenly stop. Especially when it is carrying a ladle full of molten aluminum!