2 x Schneider Electric Limited (with Ringmaster RN2C/Ring Main Unit), 1000 kVA, 1100 HV, 433 LV, ONAN cooling class HV transformers built circa 2005
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Transformer cooling class letter description
Letter | Letter position | Description |
O | 1st letter (internal cooling medium) | Liquid with a flash point less than or equal to 300 degrees centigrade |
K | 1st letter (internal cooling medium) | Liquid with a flash point greater than 300 degrees centigrade |
L | 1st letter (internal cooling medium) | Liquid with no measurable flash point |
N | 2nd letter (internal cooling mechanism) | Natural convection through cooling equipment and windings |
F | 2nd letter (internal cooling mechanism) | Forced circulation through cooling equipment, natural convection in windings |
D | 2nd letter (internal cooling mechanism) | Forced circulation through cooling equipment, directed flow in windings |
A | 3rd letter (internal cooling mechanism) | Air |
W | 3rd letter (external cooling medium) | Water |
N | 4th letter (external cooling medium) | Natural convection |
F | 4th letter (external cooling medium) | Forced circulation |