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 volt drop in the dynamo and battery system, with recommendations for improvement.
| Identifier | ExFiles\Box 62\3\ scan0465 | |
| Date | 26th November 1934 | |
| -3- Ha/Wat.2/WA.{Mr Wallis}26.11.34. Cont'd.{John DeLooze - Company Secretary} It was found that the total volt drop between the dynamo positive terminal, and the battery positive terminal at the switchbox, with a current of 15 amperes flowing, was as much as 1.1 volts. The points of largest drop were found to be the cutout, the main cables, and switchbox contacts. It would be a definite improvement, for both battery and dynamo, if this volt drop could be reduced by the use, in three positions, of heavier cable and possibly larger contacts on the cutout. With the standard regulator it was found that, even with the battery down to "fully discharged", for the battery to float on the system, the load must not exceed about 14.5 amperes. To reach a floating condition with maximum load the battery had to be discharged down to 9.80 volts on O.C. when the dynamo would balance a load of about 22 amperes. With the C.J.1 type of regulator a floating condition could be obtained with the battery in a 25% charged state and a load of about 15.5 amperes. For a larger load of 24 amperes, the battery had to be discharged down to O.C. voltage of 10.65 volts. From the battery point of view therefore, the C.J.1 type of regulator would be an improvement, but the use of this regulator increases the risk of the dynamo overheating. With the present standard regulator, and the battery in a 75% charged state, a load of 25 amperes would mean a current of nearly 15 amperes from the dynamo, which at high speeds might cause trouble. This point will be decided as a result of road tests now being carried out. Recommendations. (1) An improvement to our cutout is necessary by increasing the size of the contacts and considerably increasing the contact pressure of the same. The magnetic circuit could be improved to obtain better contact pressure by reducing the reluctance and making the coil spool cheeks non-magnetic etc. (2) Volt drop in the cables should be reduced preferably by the use of heavier cable in the main positive circuit between the regulator and the battery. | ||