without one phase may happen at the downstream side of the starter, e.g. loss wire connection at motor terminal box. In this case, monitor via regen. voltage does not help which i believe. correct me if i am wrong.
I think it is better to classify the hazardous level of that particular area first, e.g. zone 2 area, zone 1 or even zone 0. For zone 0, the most dangerous one, what u can use is Ex'd' or Ex'i' type equipment, zone 1 with Ex'e' and zone 2 with Ex'n' etc. Wrong area classification may incur high...
