Inverter building using Wiseguys Power board and the Nano drive board

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wiseguy Guru Joined: 21/06/2018 Location: Australia Posts: 1297	Posted: 03:32am 01 May 2026         phil99 said   The stated voltage limit is the continuous voltage that produces the maximum safe temperature rise. The coil is just wire, and like motor windings can tolerate a much higher start current than it's continuous rating due to the thermal mass slowing the temperature rise. The 5V relays I used were undamaged by a 1 second pulse of 24V which is far longer than the 10mS they needed to pull in. That is a big safety margin, despite the over-voltage ratio being almost 5:1. The thermal mass of a contactor coil would be much greater than for those tiny relays so the safety margin would also be much greater, especially with an over-voltage ratio of only 2:1 Edit. P = V^2 / R so for 2:1 Pmax is 4 times normal. For 24:5 Pmax is 23 times normal, yet no damage as it never gets time to reach that. Do you actually have a solution or schematic etc ? Maybe purchase a unit at ~$100 and play with it using your ideas. I was not after an argument I simply presented a working system that provides the right current during pull in time period and the right current for hold time and did not exceed the manufacturers stated maximums. What exactly did I get wrong that needed the exta posts? Edited 2026-05-01 13:35 by wiseguy