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, appropriate precautions must be taken to protect the machine to ensure that the explosive atmosphere cannot be ignited. There are four types of protection applicable 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, two machines were designed and tested to meet IEC 60079-0 and 60079-7 standards regarding the Exe II B 200°C (T3) requirement. The machines are installed in Zone 2 locations. This paper presents the electrical and mechanical design considerations of the increased safety induction machine. Finally, the paper describes the test procedure and summarizes the results from the series of tests performed on these two machines