Can Flux Weakening mess with the hall sensors?

[Dui ni shuo de dui]

Hello guys,

I recently started to have a weird issue with my motorbike. Sometimes, when running at high speeds, the bike will suddently have what feels like a big burst of regen braking, then the controller would cutoff. This happens when I have the throttle either wide opened or slightly accelerating while already at 60+ mph, it's not supposed to be in regen mode.
So that's a bit dangerous, obviously, because the wheel can lock up for a brief moment, while it wasn't expected at all to do so.

This is fairly new and seem to have started occuring recently, probably after I've set a higher current for the flux weakening.
I'm a bit puzzled as to what could be the cause.

I'm pretty sure it is not a motor phase short, because it happens quite rarely and also because the controller cuts off from overcurrent protection (so that means that the energy is somehow coming back to it). But maybe I miss something here.

My guess would be that maybe the flux weakening is messing up with the hall sensors, causing them to send wrong information to the controller and then messing out the timing. Is that even possible?
Did any one have this issue before or could provide any plausible explanation on what's going on?

Thanks a lot in advance!

 

[pwd]

I have a similar quirk when using flux weakening but it was only when I let off the throttle. I had come across this post which seemed to explain it fairly well. Maybe this is what you are experiencing?:
https://endless-sphere.com/forums/viewtopic.php?t=95174#p1401978

 

[billvon]

I recently started to have a weird issue with my motorbike. Sometimes, when running at high speeds, the bike will suddently have what feels like a big burst of regen braking, then the controller would cutoff. . . .
I'm pretty sure it is not a motor phase short, because it happens quite rarely and also because the controller cuts off from overcurrent protection (so that means that the energy is somehow coming back to it). But maybe I miss something here.

I doubt it's field weakening "messing up" the hall sensors.

Here's a potential explanation:

1) You go fast; way over base speed.
2) There is a momentary glitch in the throttle signal. Drive power to the motor stops. Since you are way over base speed, the motor tries to feed all the power it can back to the battery through the FET body diodes; you get a huge amount of torque and power into the battery.
3) The controller senses the overcurrent and shuts down.
4) The bike slows below base speed and regen stops.

 

[larsb]

Could very well be the case, what controller do you run?

Your issue would indicate a poor implementation of field weakening in the controller (so i'd stay away from that type )

 

[Dui ni shuo de dui]

Thanks guys, your explanations seem to make sense.

I'm using the flux weakening on this controller (sabvoton 72200 unlocked) for now around two years without any issue. It was set to something like 40 amps. Top speed was around 117kmh.
I just moved it a up quite a lot recently, probably around 80 amps (don't really remember) which did not actually increase the speed much, I just gained 3-5 kmh so it doesn't really worth it.
The problem appeared recently but it's very random, sometimes it can happen one or two times a day, sometimes I won't have any problem at all for several weeks.

Weird thing also is that it does not always happen at top speed, it's always happening above 90-100kmh. I didn't have the problem at all before, despite reaching very similar speeds.

Anyway, I'll try lowering it down and report if this solved the problem...

 

[larsb]

I wonder if you have another issue going on. Either a hall sensor starting to go bad or a wiring issue. It'll be interesting to hear if changing back affects the problems?

 

[Ianhill]

If this was happening as the throttle was released id say the increase current has made a higher voltage bemf spike thats creating an overvoltage situation, but to happen as your running suggests that it's either the controller losing sync, protection error of some sort or as mentioned poor field weakening.

I've only used primitive field weakening and never had an issue with stalls or lock ups thank God but there is a potential there much like the run away dc motors of the past nothing's perfect.