Ex Motors Certification

[magneticted]

If we are supplied Ex motors ( Exn, EExd, Exp etc ) and the power supply is of poor quality, i.e lots of harmonics maybe upto 5%, and the above motors are certified accordingly for a sinusodial supply. how do we stand legally operating these motors on supplies with say 2 - 5% THD. Besides maybe derating the motors how does the certification stand up.

 

[stardelta]

I think there is a lot of if`s and but`s to this answer. The motor will have been designed to perform within certain parameters as supply quality varies. I suggest you check with the manufacturer as to what the limits are and where their responsibilities end. My biggest concern would be excess surface temperature taking the motor out of its rated T class.