Study of minimum overpressure location on high tension purged and pressurized protected Ex ‘p’ motor for explosive atmospheres

Electrical motors are used widely for the different applications in the petrochemical industry. Special design requirement of such motors are achieved by applying some type of protection techniques for safe operation in the explosive atmosphere. These are four type of protection techniques applicable to high tension machine as Ex ‘d’ type (flameproof), Ex ‘e’ type (increased safety), Ex ‘n’ type (non-sparking) and Ex ‘p’ type (purged and pressurized). In this paper the study is done on the different high tension (HT) motors with purged and pressurization Ex ‘p’ protection for their minimum overpressure (Pmin) location, purging time and temperature rise on stator winding and motor body. The purging time and determination of temperature rise on the stator winding of such HT Ex ‘p’ motors are described from the series of different tests conducted on different HT Ex ‘p’ motors.

► The study of minimum overpressure (Pmin) location in the pressurized Ex ‘p’ high tension motor enclosure for hazardous area.
► Motors were designed for leakage compensation method with Px protection.
► Pmin measured on all the motors in both standstill and running conditions and then minimum purging time calculated.
► The study reveals that location for Pmin is not same in identical motors in both conditions.
► It needs to verify each Ex ‘p’ motor for Pmin to secure hazardous area.