Quote Originally Posted by pequod View Post
Interesting point John. I'm new to stepper motors, so don't understand this. The motor I've ordered is 2 phase, 2.73V, 4.2A, 3.2mH, wired Bipolar Parallel, Zapp SY60STH86-30. I haven't got the kit yet to measure. So does this mean I rate the cable at 2.1 A? This could be good.
Each pair of wires is a phase... so a 4.2A phase on bipolar means 4.2A is being carried in 2 wires. In full step mode only 2 of the 4 wires at any one time is carrying 4.2A and not 100% of the time, but the maximum current in any one wire is 4.2A.

16/0.2 is rated for 3A continuous 6A peak in conduit, at 4A you will lose about a volt across a 1.5m length.