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).
Investigation into dynamo protection and fuse behavior under different temperature conditions.
Identifier | WestWitteringFiles\D\February1920\ Scan6 | |
Date | 1st February 1920 | |
Contd. -5- Ckl/T3.2.20. B. Protection of the dynamo should at any time the cutout stick on with the dynamo stopped and the charging switch be left on. Investigation under this head was carried out by preventing the dynamo from turning as a motor and switching on with a switch acting as a shunt across the cutout contacts. The various currents flowing (no fuses in circuit) come out as follows :- Dynamo (cold). Dynamo (hot). Field current. . 2.0 amps. 1.85 amps. Control current. 18.0 " 11.5 " Main negative current. 12.0 " 10.0 " (1) In the B case now under consideration, a field fuse offers no protection. (2) A main negative fuse of 12 amperes capacity just goes with the machine in a cold condition and after which the control current becomes 24 amperes. With the machine in a hot condition, the main negative fuse of this capacity may fails to go. (3) If both main negative and control fuses of 12 amperes capacity are fitted and the machine is in a cold condition, the control fuse goes first, after which, the main negative fuse follows. When, however, the dynamo is in a hot condition, the short circuit control current is so much reduced that even with 12 amperes capacity both Contd. | ||