On 9/22/2014 9:01 PM, Dean Stuckmann wrote:
> Hi,
> Thanx for the help.
>
> Here is some more info. I did the motor testing with the motor just on the ground. So there was NO resistance from belts or the transmission. Could that cause the runaway? But like I said it worked fine in reverse. In reverse the torque made the motor jump as it got up to speed almost immediately. In forward, the motor started at just a few RPM for the first few seconds but then started revving up to runaway after about 5 more seconds.
The problem is there is no power to the field when in forward. If the
E16 uses the E15 type of field control there is a relay that is probably
welded shut in the reverse position. Thus when you try to go to forward
there is no field. If it's an E20 type controller then there are two
diodes that provide
constant power to the field in forward and reverse.
One of them blew up.
The E15/20 motor is not really a shunt motor, it's a compound motor.
There is a shunt field that supplies almost all the power, and a small
field in series with the armature that acts as a compensating control,
increasing field strength past normal full field when the motor is
heavily loaded. With the normal field gone that little remaining field
winding will provide enough to spin the motor very quickly with no load
and not at all under any load.