ARW-…[-1,2; -3; -5] (1~230V/50Hz) five-speed transformer speed controllers or RTRD [-2;-4;-7] (3~400V/50Hz) fans are intended for air flow control. Fan speeds are selected manually. The box should be supplied from main switchgear equipped with main switch breaker, differential protection as well as thermal and short circuit protection. Three sizes of the controller are available, differing in terms of power supply and rated current.