Application (BK/DK) control transformer) BK series machine tool control transformer is suitable for circuit of 50~60Hz, voltage up to 500V, usually applied as power supply for machine tool electrical appliances, locallightings and indicator lamps. Structure character (BK/DK) control transformer) According to different structures, BK transformer belongs to shell type, and according to the installation mode, it belongs to vertical type. Working enviconment (BK/DK) control transformer) 1.Ambient air temperature: -5â +40, the highest monthly mean temperature should not exceed +30â 2.Altitude for installing place should not exceed 1000m; 3.When the ambient air temperature is +40â��, the relative humidity should not exceed 50%, and it allows higher relative humidity under lower temperature. Max average humidity in the dampest month is 90%, meanwhile the lowest average temperature of this month is + 25â��, and condensation on the product surface caused by temperature change should be taken into consideration.