The CSR Edmonds EP (EcoPower) series of rooftop ventilators are the first hybrid rooftop ventilators ever tested by the Air Movement and Control Association (AMCA). There are 3 models made by Edmonds, the EP400, EP600 and EP900. The 400 is the throat diameter in millimeters as is the 600 and 900.
Edmonds engineers made the decision to add motors to their Hurricane gravity rooftops – the highest performance gravity ventilators made at the time. They decided to motorize the rotating turbine rain top using a very efficient electronically commutated brushless DC motor made by EBM Pabst.
You can see the details of their designs at the web site of their United States Distributor, Edmonds USA. http://www.edmondsusa.com/