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).
Analysis of the burning of cutout and dynamo switch contacts based on different circuit configurations and switching sequences.
| Identifier | ExFiles\Box 65\2\ scan0112 | |
| Date | 16th May 1928 | |
| EFC {E. Fowler Clarke - Electrical Engineer} 4/T16.5.28. BURNING OF CUTOUT CONTACTS AND DYNAMO CHARGING SWITCH CONTACTS AS AFFECTED BY CONNECTION OF CUTOUT SHUNT COIL AND ORDER OF BREAKING DYNAMO CIRCUIT (i.e. DYNAMO ARMATURE OR FIELD FIRST). We have carefully considered the effects in the four cases and also confirmed these by actual trial on the bench. The four cases are the four combinations of the two pairs of alternatives - (A) Positive end of cutout shunt coil connected to distribution box terminal B, or alternatively to terminal C. (B) Charging switch breaking dynamo field first and armature second, or alternatively dynamo armature first and field second. The various cases with the results in detail are as follows :- Case 1. Cutout shunt coil positive connected to distribution box terminal B. Charging switch breaks field first. On switching off, a normal field breaking flash occurs at the first break (field). The battery is momentarily left connected to the cutout shunt coil, the cutout only remains in momentarily until the reverse current from the battery through the dynamo, cutout contacts and series coil, has grown to a sufficiently high value to throw out the cutout. The cutout comes out with a small flash. Subsequently, in breaking the armature connection, this is broken dead unless the operation of the switch has been very quick and so quick as to be unlikely to happen, in which case there is a small spark at the break. Case 2. Cutout shunt coil positive still connected to distribution box terminal B. Charging switch now breaks armature first. On breaking the armature circuit there is a considerable main current flash at break. The battery is for the time being left connected to the field circuit of the dynamo, via the cutout contacts and series coil, and therefore the dynamo is still (separately) excited and keeps up a high voltage which operates on the shunt coil of the cutout and keeps this in; on subsequently breaking the field | ||