Using an Alltrax Controller
in the NB2 Locomotives

The NB2 locomotive was sold to a new owner. I didn't want to leave him with a one-of-a-kind home-built controller. The alternative was to retrofit a stock off-the-shelf unit from a company with a good reliability record. This way, the new ownwer has access to technical support and replacement parts.

I replaced the Dash-2 controller with this Alltrax AXE 2444P model. The "P" indicates "Plug Braking" which I later found unsuitable for this application. It just wasn't reasonable to ask the operator to apply throttle while going downhill and shove the contactor into reverse to force the unit into plug braking mode. Just a bad idea.

So I moved the reversing contactor to the armature winding so that in neutral the armature would be shorted. Then I added the braking relay to apply PWM from the controller to the low current field winding to vary the braking effort. This solution works very well. Now the operator only needs to apply throttle in neutral to apply braking in either direction.

Go HERE for a schematic of this modification.