Previously, we said that if your motor supply doesn't conform to Art. 430, you'll have a "high maintenance" situation. Conformance with Art. 430, however, doesn't necessarily produce a "low maintenance" situation. Not even in an NEC sense.

For example, consider voltage drop, per the informational note in 210.19(A). You calculate this during the design. If you try to measure it in an installed system, you actually measure a combination of voltage drop and losses (through insulation and across connections) in the run. This measurement can reveal that something is wrong. If you measure 430V at the supply terminals to a 480V motor, you don't need to calculate voltage drop to know you have a problem. But what exactly is the problem?

To answer that question, calculate the voltage drop between the motor and its supply. Then, compare that to the measured voltage loss. If the two numbers are close, you have a design problem — undersized conductors. As the numbers grow further apart, your problem is increasingly a maintenance one.