I am looking at specs of an air conditioner unit. It uses DC inverter technology and maximum current listed as 21.5A

So are DC inverter motors considered resistive or inductive? What utilization category this device is in? AC-21, 22 or 23?

Because I am looking for an isolating/safety switch and it is rated for AC-21 as 40A but 25A for AC-22 and 20A for AC-23 https://www.katko.com/fi/tuote/kum-116u/ So it is difficult to decide if this switch is underrated for the air conditioning unit or not.

So the question is what current rating should the isolating/safety switch should be for use with 21.5A DC inverter motor system? Obviously the answer also depends on the utilization category that the spec is based on...


  • $\begingroup$ If I'm understanding the construction well enough, the power path is AC -> inverter -> DC motor. If that's the case, then the inverter could appear to the AC as just about any sort of load. If care was not taken in its design it'll look capacitive, but the inverter manufacturer could well have made it look resistive, possibly with some in-rush current. So -- check to see if there are specifications, or see if you can get the manufacturer to talk. $\endgroup$
    – TimWescott
    Nov 1 '19 at 19:21

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