From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Test report page detailing failure modes of an electrical cut-out, comparing 'Armature break first' and 'Field break first' scenarios.
| Identifier | ExFiles\Box 65\2\ scan0025 | |
| Date | 23th February 1929 guessed | |
| Contd. -2- (2) Armature break first. Failed after 16843 operations. No spark at cut-out on opening. Points not badly burnt. Small groove burnt in under-side of blade. Also slight groove in top side. Top finger (field) slightly burnt; lower one badly. Cut-out connected to terminal C. (3) Field break first. Failed after 64806 operations. Very slight spark at cut-out on opening; points not badly burnt. Groove burnt in under side of blade. Lower finger (field) burnt. Top side of blade and finger as new. (4) Armature break first. Failed after 24363 operations. Heavy spark at cut-out on opening; points badly burnt. Groove burnt in under-side of blade. Lower finger (armature) burnt. Top side of blade has a bright groove but finger is O.K. Reason for this is not clear but may be due to accidental removal of vaseline which was applied before each test. The condition of the cut-out points is partly affected by sparking which occurs on closing and which is the same for all cases. The points were trimmed before each test. In all cases there was a small amount of copper dust deposited around the switch contacts on finishing the test. The experiment shows the superiority, by a good margin, of breaking the field first, even allowing a Contd. | ||