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 on the effects of over voltage on a 20 HP dynamo.
| Identifier | ExFiles\Box 50\5\ Scan381 | |
| Date | 23th October 1925 | |
| X4333 EFC. AC.62. 23rd Oct. 1925. X.4610. X.4333 EFFECTS OF OVER VOLTAGE ON 20 HP. DYNAMO. In order to observe the possible effects on brush bedding and consequent output on 20 HP. dynamos when run at abnormally high voltages such as sometimes occur on chassis, a machine in standard condition (N.288) with brushes and commutator well surfaced, etc. was put on the direct coupled rig and run at its peak load, operating at between 18 and 20 volts. The output under these conditions was, when fully hot about 12 amperes. The run continued for about 9 1/2 hours at the end of which it was found that the brushes were in slightly inferior condition to that in which they started, the trailing halves of the contact faces being darkened a little, more noticeably on the positive brush. The commutator was much blackened but not pitted or burnt. The solder, however, was thrown from the spokes although the armature conductors were not thereby disconnected. The general result of the test is that over-loading of the dynamo willnot upset the bedding of the brushes and alter the output. The firstf fault likely to occur is the throwing of the commutator solder. This is what has happened on machines which have failed due to running on open circuit on cars. FJA. | ||