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).
Examination of faulty coils returned from customers, detailing a partial short circuit on the secondary winding.
| Identifier | ExFiles\Box 69\1\ scan0275 | |
| Date | 13th December 1929 | |
| X 8710. EV{Ivan Evernden - coachwork}/RD. from EFC. EFC3/AD13.12.29. X.8710. EXAMINATION OF FAULTY COILS. RETURNED FROM CUSTOMERS. Further to our EFC5/AD10.12.29, we have now unwound the two coils NQ.95 and VI.85 after having confirmed the fault in each case to be due to a partial short circuit on the secondary winding. The following points were noted :- NQ.95. Breakdown at the end of the 2nd. layer close to flexible connection to primary. VI.85. Breakdown at the end of 2nd. layer. Primary flexible connection found well underneath the 2nd. layer causing the layer of paper insulating that layer to be unduly stressed mechanically. This has been suspected on all the six coils recently unwound, and it is suggested that it may be the cause of the failure of the first layers on these coils. The effect is as follows [Handwritten diagram with labels: 'Insulating paper', 'Paper stressed here', '2ND secondary layer', 'first secondary layer', 'Primary connecting flex'] In the case of VI.85 coil, the short had occurred about 1/2" along the circumference of the turns, suggesting that the paper had been sheared. EFC. | ||