Strong hub motor vibration, although hall sensors seem to work

[chris09]

Hello everyone,

My drive system worked flawlessly for a few weeks, but suddenly I came across an issue that made my electric scooter unridable.
*btw I wanted to post this in the E-Bike section because i have seen more similar issues here so this will more likely help someone else as well and the tech is very similar.
Here is the problem:
When I increase the current my hub motor (not geared, rated for 350W and 800kv, running on 48V) starts vibrating so strong that it can not accelerate the scooter, even when the scooter is moving. Without any load it is at least able to start and reach max RPM. If i increase the current too much, the motor lurches and the VESC (Version 4.12) cuts the throttle.
First I assumed that it was an issue with the hall sensors, so I checked them all and found that when the wheel is rotating they all change from 5V to 1,87V, none of them had a constant voltage.
I wonder whether its a problem that they dont change from 5V to 0V. But the motor has a significantly better starting performance without stuttering when the hall sensors are connected and the VESC always detects all 3 of them without showing any issues.
My ADC throttle input is nice and linear, thats not causing the issue.
The motor wires are connected firmly and are not damaged.
The problem occurs in BLDC and FOC pretty much the same way, I am using the exact same values as before when it used to work.

I have thought about this and tested the whole day but I just cant find a solution.
I would really appreciate any help or thoughts you have on this!!
If I should give more details about something please tell me.(if needed also in form of photos/videos)

Thanks!

 

[AngryBob]

OK, first and foremost, "something" happened, in between when it DID work, and it did NOT work. Possibly some hidden, unseen, mechanical defect, but also, and in fact most frequently, there may have been some obvious, observable strange or unusual event. Think hard what that may have been, most likely happened when somebody else was using the unit.

Now, what you are describing, does sound like mismatched halls, or phase wires, but it sounds like you have checked those, and there seems to be no defect, OUTSIDE the motor. Have you checked for internal wiring issues, especially if the unit was run especially hard or fast or long, during that inbetween time mentioned above? Partially melted phase wires with a short internal to the motor seems likely, again, depending on preceding events.

At ebikes.ca, or grin, there is a test for shorted phase wires that is simple and non-destructive, there is a caution about MINIMAL throttle usage during the test, read carefully. IIRC it starts with disconnect controller, check for relatively free motion, then short pairs of phase wires, etc, but go to the source for exact details.

Report back with test results and any other observations or solutions.

Some other thoughts, can you free spin the wheel and check for axle issues? Free-ride using leg power to decent speed, maybe downhill, check for wheel wobble and also apply throttle on the downhill, when load is lessened for the same speed? Any clunks or rattles like a loose or detached magnet might cause?

 

[dogman dan]

Hall sensors that don't toggle between 5v ( or whatever the input is) and 0v as they rotate are not working.

But if the problem persists when running sensorless, then the problem is in the three power wires. Often when it runs smooth no load, and stutters with a load, its because one wire is connected, but for some reason can't carry much current. Bad plug, nicked wire, that sort of thing. And of course, the problem could be you cooked off your motor. That's what often kills halls.

 

[chris09]

Complicated problems often have simple solutions.
Before the problem occured I wanted to resolder the jumper wire on my anti spark plug what due to some reason created a tiny bump on the plug (probably got too hot) that prevented me from plugging it in all the way through. But I didnt thought that this was an issue because the VESC always had power. Turns out it was the issue. I sanded the bump down, plugged it in all the way through and the vibrations were gone :thumb:
Im glad that neither my motor vor vesc were broken.

If someone is interested in a more detailed explaination on why an anti spark plug can only work when fully plugged in and how it exactly works then i could write another post.

Thanks a lot for your troubleshooting advise and ideas!!

 

[amberwolf]

If the "jumper" part of the antispark, with the bump, that woudln't plug in all the way, is actually the current-carrying part, and the part that plugs in first is the actual antispark part, then that's why it didn't work right until this was fixed.

The current was being "bottlenecked" at the poor connection.

 

[AngryBob]

I just had to reply to this, perhaps request making this thread a sticky, because is is just so -

You had a nice, perfectly working system, and then .... YOU MESSED WITH IT.

Then, IMMEDIATELY AFTER, you know, YOU MESSED WITH IT, it did not work anymore.

Just to make clear, it WORKED, absolutely nothing else happened before YOU MESSED WITH IT, nothing else happened after YOU MESSED WITH IT, and then it no longer worked.

And... it gets BETTER.

You post here, wondering what could POSSIBLY have gone wrong, conveniently and freaking amazingly leaving out the part where YOU MESSED WITH IT, and totally waste everybody's time trying to figure out what went wrong.

All this, while being perfectly aware, that after YOU MESSED WITH IT, it did not go back together as it should have.

You know what is really sad? This no longer surprises me at all. It is what I expect to happen. Because it so very often does.

It does not make me angry that YOU MESSED WITH IT. What makes me absolutely boiling mad furious is that you KNOW that YOU MESSED WITH IT, you KNOW that right after that it did not work anymore, you KNOW that is likely a vital piece of the puzzle, and STILL you say nothing. You are freaking anonymous, I can't hit you with a hammer from here, you can disappear and come back with a new name, there is ABSOLUTELY NO DOWNSIDE to telling the truth, and still you lie and deceive and waste other people's time who are just trying to help you out.

 

[FarmerFpv]

100% agree, what's the point of asking for help without all the information.

Cheers