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Post by tubeprune on Mar 10, 2009 6:54:12 GMT
The picc stock was designed for weak field running but I don't think it was selectable. There was no weak field flag switch and the weak field came in automatically at the end of full parallel untill the mods in 1938. TP What do you mean by two stages of field weakening. I can only see one. Darren. You add another resistor and relay.
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Deleted
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Post by Deleted on Mar 10, 2009 10:58:54 GMT
Thanks TP. How was the second shunt field resistances controlled. Did they use another shunt field relay working off the demand current of the motors that was selected by the weak field flag.
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Post by tubeprune on Mar 10, 2009 13:34:16 GMT
Thanks TP. How was the second shunt field resistances controlled. Did they use another shunt field relay working off the demand current of the motors that was selected by the weak field flag. Probably but I don't know for sure. I no longer have my pre-38 stock car examiner's schematics. What is obvious is that the late Graeme Bruce was not correct in stating that shunt field operation was new on the 1930 Watford Replacement Stock. The earlier stocks had it but it was automatic and single stage. There are two options: Either they added a second FS relay activated by the flag switch so that the first stage continued to be automatic while the second stage was under the control of the flag switch or they made the operation of both stages flag switch operated. For 38TS, both stages were flag switch operated.
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