Using EEx d/de motors with inverter drives: keep your options open

In the past, motor users have been advised that flameproof EEx d/de motors and inverters need to be tested together when used as a system in a potentially explosive atmosphere. Dr Donald Jackson, Technical Director of Brook Crompton, argues that this is not necessary if a motor certification capable of using any inverter is established at the outset

The introduction of the ATEX Directive in 2003 — and the inclusion, in July 2006, of site risk assessment from DSEAR (the Dangerous Substances and Explosive Atmospheres Regulations) — established the need to review and identify areas where potentially explosive atmospheres may occur.

Typical hazards include the risk of abnormally high temperatures or the risk of sparking. The application area is categorised according to the gases or dusts present, and the likely period of exposure, as shown in in the table below.