Cable and Starter

[Timm1]

I am confused that up to what size “motor feeder cable” can be protected by a motor starter. For example, a 75HP 460V motor needs Size 4 starter. This motor has a full load amperes of 96 amperes, which means that the conductor with ampacity of 96*1.25=120A (# 1 AWG) should be used.

I understand that the size 4 starter will protect the # 1 AWG cable. But what if instead of #1AWG, I use a bigger cable (say 2/0.) Will the size 4 starter have the capacity to protect this 2/0 cable?

Your response will be highly appreciated.

 

[jraef]

Think it through a bit.

You changed the cable, but did you change the load?

If the starter trips at 96A, is the 2/0 cable going to have a problem carrying 96A?


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[TurbineGen]

In short, yes. Larger cable can handle more current. In our plant we often increase the wire a size or two to allow for an increase in motor power in the future without having to run new cables.

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