Design of increased safety electrical machine: Development activities and certification testing

Electrical machines are used widely in the petrochemical industry. Most of the machines are operated in Class I hazardous locations and, hence, approp riate precautions must be taken to protect the machine to ensure that the e xplosive atmosphere cannot be ignited. There are four types of protection a pplicable to large machines. They are type p (purged and pressurized), type e (increased safety), type d (flameproof), and type N. Type p, type e, and type d protections are permitted in Zone 1 or Zone 2. In 1996 and 1999, tw o machines were designed and tested to meet IEC 60079-0 and 60079-7 standar ds regarding the Exe II B 200 degreesC (T3) requirement. The machines are i nstalled in Zone 2 locations. This paper presents the electrical and mechan ical design considerations of the increased safety induction machine. Final ly, the paper describes the test procedure and summarizes the results from the series of tests performed on these two machines.