690v 3 Phase Motor Leads

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NevadaSteve

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In a 3 phase 690v motor, can individual feeder lead wires rated at 600v be used since the actual voltage (to gnd) on each leg is only 690/sqrt3 = 399v? When 2 leads are next to each other (i.e. 690v potential between each conductor) then you have 1200v's worth of insulation.....is this totally wrong?
 
In this country, 600V is the max., and since you have >600V phase-to-phase, your cable must be rated for that and per the NEC Article 100, 690V would technically be MV (i.e. "over 600V"). 690V is an overseas voltage standard so the NEC would not make allowance for it.

Do you really have 690V for use here? If so, you can get XHHW that is rated for 1000V fairly easily. Curiously, LV SWITCHGEAR can include up to 1000V, but not the wiring.
 
Jraef...thanks for the feedback. The application is not in the US, so NEC is not the governing body, rather an overseas application governed by IEC. The cable in question is a custom teflon with a stainless steel braided armor for a hazardous area application and is only available in 600v or 8kV. I don't think the 8kV version is available in the gauge I need. I have been looking through IECEx standards and have't found anything which speaks directly towards this, however, there are a multitude of IEC standards out there that cost a bunch of $ that may or may not be applicable.

I may add a layer of acrysleeving over the top to up the insulation value of the 600v cable by another 1kv and go with it.
 
I run into this a lot with large 250kva+ UPS systems. The battery bank is often center tapped so you have +/- 500v or more to ground. That's 1000v between the end conductors. I just specify "rail road" wire which is rated at 2kv
 
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