Introduction The use of electrical motors in potentially explosive atmospheres is quite frequent these days. These motors have to be constructed in such a way that there is no risk of an explosion. An Explosion occurs when the following situations occur: - presence of potentially explosive atmosphere - existence of a source of ignition - possibility of transmission of the explosion

Application Groups Depending on the intended use, explosion-proof electrical operating equipment is divided into two major groups: Group I Equipment for coal mines (only specially designed motors for mines can be used) Group II Electrical equipment for use other than mines (surface industry) Group II motors with flameproof enclosures are still further divided into gas groups: II A ~120 gases and vapors, e.g. butane / petroleum /propane II B ~30 gases and vapors, e.g. ethylene / dimethyl ether II C limited number of gases and vapors, e.g. hydrogen H2 / acetylene C2H2 / carbon disulfide CS2

Temperature Classes Combustible gas or vapour and explosion-protected electrical equipment are divided into temperature of the gas up to T6 with regard to the ignition temperature of the gas or vapour and the maximum surface temperature of the component.