trolley wiring

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aaatraker

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We are installing a powered rail system that is used for cranes and trolleys. I,m concerned about the way its designed, not sure how it should be wired and protected.

There is 480v three phase power run inside of a plastic rail, using flat copper bus, with a ground bus. A wheeled assembly runs inside the rail with three spring loaded connectors that ride aganst the surface of the flat bus, three per phase. Each connector has a # 10 wire that hooks to the same lug in a connection box.

I,m being told this is a parallel connection like those used in a switchgear feed,
that each wire handles 1/3 the load and rated for 30 amps with a 90 amp total rating.

The feed to the rail is 125 amps. Wire is 1/0 from breaker to rail connection box.

The powered assembly will connect to a timber tote used at a sawmill, running hydraulic motors, and transformed also for control power.
It is a ul listed system.
Questions:

Is it a true parallel connection?
How do I protect the #10 wires correctly?
What else do I need to do to make this a correct installation?


Thanks
Kurt
 
charlie b

charlie b

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Semi-Retired Electrical Engineer
I have designed power systems to crane rails before. Those were 4160 volt cranes that serve container ships. But the method by which power is conveyed from the rail to the components on the crane is essentially the same as what you have described.

It is not a ?parallel circuit,? in the view of the National Electrical Code. That is because the NEC has nothing to say about how a manufacturer designs and installs wiring internal to a manufactured item. If it is UL listed in the configuration you describe, then you are not responsible for protecting the #10 wires. You provide power to this item?s single point of connection, using the 125 amp breaker to protect the 1/0 branch circuit conductors from the panel to the machine.

NOTE: I am not in easy reach of an NEC at the moment. So I cannot verify that a 125 amp breaker is the proper choice for a set of 1/0 conductors. Someone else may have a comment on that aspect of your question.

All you have to do to make this a correct installation is to install it in the manner described by the manufacturer.
 
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