(ET) E-20 motors

["Rhett T. George" <rtg ee duke edu>]

 - Greetings -

Thanks to all who persisted in telling me that the E-20 was compound
and reversed the armature rather than the field.  I am corrected, 
chagrined, and smartened up.  You are good folk.

Regarding what goes where, the factory schematics show a series winding
internally connected to the armature.  The terminals are one pair for
the armature and series field and the other pair for the shunt field.
The armature terminals may be marked A1 and S2.  The shunt field may
be connected with a two-conductor plug.  Wire numbers are 8 to A1,
24 to S2, 62 to P6-1 (plug?), and 36 to P6-2.

The motor may be cumulative compound in the forward direction.  If so,
this will give extra torque in cases where the load torque demand is
increasing.
 
If the unloaded motor is connnected thru only the armature circuit and 
the starting resistors to 6 V, it will be a series motor on low voltage 
and should not run away.  It it runs the same direction as when connected 
normally, the series field is providing magnetic flux in the same direc-
tion as the shunt field provides > > cumulative compound.  Should it 
rotate in the opposite direction, then it is differential compound.
If you have to help the motor to turn, it should be much easier in one
rotation than the other.

                                        Rhett George