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).
Modifications to dynamo armatures to increase current output at high speeds.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan150 | |
| Date | 9th January 1931 | |
| To R.{Sir Henry Royce} from EFC. c. Sg.{Arthur F. Sidgreaves - MD} c. Wor.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} c. PN.{Mr Northey} Da.{Bernard Day - Chassis Design} Hs.{Lord Ernest Hives - Chair} [STAMP: RECEIVED 24 JAN 1931] [STAMP: ORIGINAL] X.6084. EFC3/AD1 9.1.31. DYNAMO OUTPUT. R3/M6.1.31. To obtain more current at high speeds without too far raising the cutting in point of the dynamo, a promising immediate modification appears to be that of increasing the size of slots and reducing the size of teeth. By this means the reluctance of the magnetic circuit is increased at a point where it gives us the big advantage of providing for an increase in conductor size. The permeance of the magnetic circuit at other places will be kept up as high as possible. We are urging an armature through in which this principle has been adopted. At the moment we have gone one stage only i.e. increased the conductor size by one wire gauge. If the teeth are still strong enough to stand the milling a further stage in this direction may be indicated. By this means we expect, (on the 56 coil armature on which the modification is being made) a 20% increase in output with very little increase, if any, in the cutting in speed -- we are reverting to a .015 air gap in place of the standard .022 as it is expected that the big increase of reluctance through the teeth will more than compensate for this. It has even occurred to us as being not an impossible proposition actually to use a smooth cored armature for a machine which has to function in the particular way suited to chassis conditions. Apart from driving pegs for the conductors all the armature periphery would be available for them. The simultaneous rise or fall of voltage and amperage of a chassis dynamo arranged for output speed control by being connected to a battery, is not limited to those of the simple third brush type but is a universal characteristic of any type of machine, the armature reaction control of output of which with speed is dependent | ||