The amperage capability of a cable depends upon its size in diameter/conductors and its length. It is also cooling dependent. The cable must be cooled at each end or water cooled its entire length. Its ampacity varies depending upon each of these variables. Most cables are cooled at each end. The chart below gives amperage for cables of this type.
Based on the above chart a 750 MCM air cooled cable is rated at about 1400 – 2700 amperes depending upon length.
For comparison a water cooled 750 MCM Cable is rated at approximately 12,000 to 37,000 amperes at the above lengths.
Water cooling increases the ampacity substantially.
Sizing of the cables is discussed in the article:
HOW DO YOU SIZE THE PRIMARY CONDUCTORS FOR AN AC RESISTANCE WELDING TRANSFORMER?
Reference: National Electric Code
RWMA Manual Chapter -21.7
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