I normally use Siemens Inverters but have recently acquired a Mitsubishi E520 1HP inverter. I'm testing on a 1hp 3phse motor loaded with an 18" fan. It seems to work ok but irrespective of set speed there is a constant frequency medium pitch whine from the motor which is quite audible up to the point there the motor and fan noise dominates.
Does anyone have experience of these inverters? Is this noise normal? The same motor run on a Siemens Micromaster inverter does not make this noise.
Any info gladly received.
TIA
Bob