KT controller and direct drive motor, suddenly vibration and noise

[Julez]

Hi guys,
all of a sudden, my bike showed some problems today, maybe you can help.
Relevant information:
I have this controller (converted to IRFB4110):
http://www.groetech.de/index.php?main_page=product_info&products_id=849
Motor: Heinzmann Direct drive front wheel
Battery: 16s LiFePo (50V)
Display: https://de.aliexpress.com/item/1005004708198042.htm
Images: https://imgur.com/a/tTuFe

Age: 4 years/ 13,000km

Problem: Today I noticed that the motor does not spin the way it usually does. When lifted off the ground, the wheel does not spin up on it's own with hand throttle or pedal sensor. When accelerated by hand a bit, and then throttle is applied, it spins up, but it makes a loud howling noise and there is strong vibration noticable. There is also vibration when the motor is switched on while driving. Regen braking also causes vibration and noise. When no throttle is applied, the wheel spins silently and smooth. A mechanical problem is the least I assume.
I already checked the hall sensors: Supply voltage is 4.2V, and all 3 sensors switch back and forth between 0.2V and 4.2V when the wheel is slowly rotated by hand. Die Display does not show any error codes.
Does anyone have any idea what I could check next?

Thanks,
Julian

 

[Chalo]

If your Halls are good, the next thing I'd check is continuity and condition of the phase and Hall wires and plugs, then the controller FETs. Look for arc or heat damage to one of the phase connectors.

 

[Julez]

Hi Chalo, thanks for your reply.
I just recalled a strategy to check if the spark plugs or injectors are to blame if an engine suddenly runs like a bag of pebbles.
Disconnect them one ofter one and if it does not further decrease the running smoothmess, then this part is likely at fault.
So I disconnected the phase wires one by one. With the first wire disconnected, nothing changed and the running behaviour was as erratic as described. With the other two disconnected one after one, nothing moved at all.
So I assume that phase 1 does not get any electricity, either due to a broken cable or burnt FETs on this phase.
I will check this now.

Edit: Ok, I found the problem. The 1. phase wire has been damaged where it came from inside the frame to the headset and was exposes to bending movement always. A little fumbling, and it had continuity again, and the motor ran normally. So I will replace all 3 cables to be sure.

 

[Chalo]

Edit: Ok, I found the problem. The 1. phase wire has been damaged where it came from inside the frame to the headset and was exposes to bending movement always.

Good job finding the problem, and a good method. I'd say this constitutes more evidence (not that we needed any) that inside the frame is usually the wrong place to run cables and hoses. At least it is if you want your bike to work correctly instead of look a certain way.

 

[Julez]

Yes, there is certainly room for improvement. The next time it fails, I will redesign this region in a way that the moving cables can be very quickly replaced with Wago connectors or something like this on both ends.