Re: (ET) Alltrax output!

["subscriptions aeolusdevelopment com" <subscriptions aeolusdevelopment com>]

>Christopher Zach Wrote
>However would it be possible for the Altrax without field weakening to 
>put more amps into the armature? If the field is at full power, then the 
>limit is the battery voltage; the motor can only pull so much current 
>with a full fixed field. Unless the Altrax steps up the voltage.

That limit (max current at full battery voltage) is the same regardless of
the field strength.  It's only when the motor starts moving (a rather
important distinction) that the field strength starts imposing a limit on
the armature current.  Up until that point the only limit on current is the
resistance of the armature, brushes, cables and battery.  At full field you
will get quite a lot more torque for a given current than at a weak field
but the peaks can still be very high and certainly high enough to take out
an electronic controller.  

As an aside I just measured an application using a contactor controlled PM
motor and observed a 30 to 1 variation between peak and running current.

The controller will have limited the current for one of three reasons, 
  to protect the controller
  to protect the motor
  to limit the torque (either for feel or to protect the drive train)

Limits set for the latter may be adjustable through the controllers setup,
the first will be fixed.

Robert


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