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).
The wiring and function of a four-terminal unit for indicating high water temperature or high voltage system faults.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 44 | |
| Date | 18th April 1925 guessed | |
| and if with three, as to whether the common terminal should be on the top or positive side, or on the bottom or negative side, and our final conclusion is that the unit should be made with four terminals and be connected as shown on the diagram, in which the operating coil or heater, as the case may be, is connected between the 'te dynamo terminals A and B of the distribution box and the contacts which are operated thereby are between the ammeter side of the main fuse in the distribution box and the live terminal of the high water temperature indicator lamp, whose other terminal is connected to earth. It will be seen that the unit will function corresponding to a break in the dynamo battery circuit anywhere as mentioned in (c) above, but not in that portion between the dynamo commutator under the negative brush, and the corresponding A terminal on the distribution board, i.e. it would not show danger when there was a sticking negative brush leading to a high voltage operative upon the dynamo field, (remembering that the auto switch is not, for the present, considered to be included in the diagram). The relay would be set to operate at about 16 1/2 volts and the lighting of the lamp in question, would mean that something was wrong, viz. (1) Water temperature too high, (2) Voltage of system too high and charge must be switched off either by main switch or auxiliary dynamo charge switch if installed (We may remark in passing that the independent switch for switching off the charge would of course be (in the absence of the other units) between the two C terminals of the dynamo and distribution box respectively, i.e. it simply makes a break in the field circuit). Contd. | ||