# Sevcon Controller Help Needed / Encoder calibration



## kennybobby (Aug 10, 2012)

i don't know that controller, but it sounds like an instability in the compensation or feedback network during coasting. Are there settings for regeneration and where does the excess energy go during regen--is it setup to return to the pack or is it passed to a resistor to dissipate as heat?

If the encoder were not aligned then it seems like it wouldn't work well under acceleration and to high speed? So i suspect the issue elsewhere.

What kind of motor is it, what sensor is used for commutation, are there any other sensors for feedback such as hall sensors, tachometer, resolver, etc.? How are you using the controller--to do torque control (with current feedback) or speed control (with ? for feedback) ?


----------



## Robzim (Sep 7, 2020)

Thank you for your reply.

For the moment, I don´t add the regeneration that´s why I don´t explain this problem.
I use an axial flux motor (PMS 156 96vdc) in torque mode with a sin/cos encoder.

Do you think the speed gains could be the explanation ?


----------



## Robzim (Sep 7, 2020)

Please find pictures of the throttle parameters ...


----------



## kennybobby (Aug 10, 2012)

i don't see any speed gains to what values are you referring?

What is proportional braking? Why is it "Yes"? What is Proportional speed limit in drive? why enabled?

Whenever you let off the throttle without some sort of regen control, there is going to be an over-voltage situation on the HV buss as the kinetic energy from the spinning rotor needs some place to go. The back-emf from the spinning rotor will be acting to pump up the voltage on the buss thru the body diodes of the FETs. Maybe this increase in voltage is causing the controller to get confused?

What is the meaning of the User Defined Char Pt voltage and values?

How about renaming this topic Sevcon Controller Help Needed, then some experts might see it and join in. i don't know this controller.


----------



## Robzim (Sep 7, 2020)

The parameter Proportional braking is available only when we add the electric braking.
The proportional speed limit is disable means speed limit is fixed.

Your reasoning is interested. I have to check this.

The user Defined char is just when you want to create your own throttle input.

Please find in attach file the picture of speed gain.

Thanks a lot.


----------

