06-11-2021, 04:50 AM
hi Simon
I recall a North Shore A7 special builder. whose distinctive name I have forgotten,recounted on here experience of field coil rewinding. Curiously he used ordinary modern varnish .
Adjustable main brushes are supposed to be set for mimimum sparking at normal full output.The 4 pole DEL ones are adj but I have never fiddled with.
It is helpful to know that 2 pole armatures are wound 1 to 2 to 3 etc to 1, but the 4 pole are more involved. 1 to opposite Op, to (1+1) to (Op +1) etc or somesuch .The 3rd brush position is puzzling . 4 pole motors can have 4 brushes as starters with pairs commoned. The 3rd brush is located realtive the missing virtual brushes, instead of being awkwardky between the real two.
If the field is reversed the generated voltage cancels the residual and wont start to generate, although will motor one way or other.
I recall a North Shore A7 special builder. whose distinctive name I have forgotten,recounted on here experience of field coil rewinding. Curiously he used ordinary modern varnish .
Adjustable main brushes are supposed to be set for mimimum sparking at normal full output.The 4 pole DEL ones are adj but I have never fiddled with.
It is helpful to know that 2 pole armatures are wound 1 to 2 to 3 etc to 1, but the 4 pole are more involved. 1 to opposite Op, to (1+1) to (Op +1) etc or somesuch .The 3rd brush position is puzzling . 4 pole motors can have 4 brushes as starters with pairs commoned. The 3rd brush is located realtive the missing virtual brushes, instead of being awkwardky between the real two.
If the field is reversed the generated voltage cancels the residual and wont start to generate, although will motor one way or other.