My 250W hub BLDC motor is very noisy at less then 10km/h

[oleka]

Hello !

I electrified my 26 inch bike with a front 250W hub BLDC motor "TranzX" and a controller PSBL36V500W made by Persino from China.

Speed, torque climbing is definitely OK, but motor (and even controller itself) is very noisy at speed less then 10km/h.
At larger speed it becomes relatively silent.
I opened this motor, but planetary gears were like new and well lubricated.
Front wheel has no loose parts that could be squeaking.
What is the problem here ?

 

[dogman dan]

Likely you are hearing motor "grunting". That's what I call it anyway. Under heavy loads, the stator coils can vibrate as the controller turns their power on and off. Some motor's windings have some looser wire than others, so one motor may grunt a lot, the other very little.

When the motor rpm increases, the magnet passes the phase that is turned on much faster, so no grunting then. At low rpm, the phase is pulling hard, but the magnet, due to the load is barely moving. So the winding will vibrate as it pulls hard on the magnet. As the motor speeds up, the magnet is now whizzing by shortening the period that phase is energized, and it's pulling less hard as the load decreases.

Summing up, the phase wires in the winding don't vibrate if the magnet moves fast enough and the load is low, but they do when the magnet is not moving, or moving slow, which happens when the load is big.

Some controllers grunt too, from vibration of the fets. They are bolted to a heat sink, but they can vibrate the whole board inside.

 

[oleka]

So maybe I need to dissassemble the motor again and treat the windings with a transformer varnish ?
When being dry it has some residual mechanical softness that may prevent the windings from fringing.

 

[dogman dan]

Not sure if that will be effective or not. Worth a try if the buzzing is really bad. The buzz may be deep inside, where more varnish can't reach it.

 

[Nobuo]

Likely you are hearing motor "grunting". That's what I call it anyway. Under heavy loads, the stator coils can vibrate as the controller turns their power on and off. Some motor's windings have some looser wire than others, so one motor may grunt a lot, the other very little.

When the motor rpm increases, the magnet passes the phase that is turned on much faster, so no grunting then. At low rpm, the phase is pulling hard, but the magnet, due to the load is barely moving. So the winding will vibrate as it pulls hard on the magnet. As the motor speeds up, the magnet is now whizzing by shortening the period that phase is energized, and it's pulling less hard as the load decreases.

Summing up, the phase wires in the winding don't vibrate if the magnet moves fast enough and the load is low, but they do when the magnet is not moving, or moving slow, which happens when the load is big.

Some controllers grunt too, from vibration of the fets. They are bolted to a heat sink, but they can vibrate the whole board inside.

Nailed!! from my not expert opinion, I guess that if a motor goes more or less smooth silently from 50% to 100%, noises, and trembling on uphill is something more or less normal. Maybe is needed to have the feel of more combinations of controllers and motors to understand what should be normal or not.

I have a question!. Are sine wave controllers solving the grunting sound? or it depends half the thing about the motor

 

[oleka]

I started disassembling my motor but now I'm stopped - not sure how to proceed. I removed gears plate and all retaining rings.
Here are the pics of this motor as of now:





How can I disassemble it more not destroying it ?

 

[docnjoj]

Can we see a photo of the gears? Are they metal? Also I only see 2 wires coming out of the motor. Are there more wires exiting the motor?
otherDoc

 

[oleka]

On the pic, there are 2 cables because the rest is not well shown.
There are 3 power cables and 5 cables for halls and an extra one (white) that is not connected to anything. Maybe temperature sensor ?

Here are the gears:

 

[d8veh]

A sinewave controller does make a big difference. Try the S06S from BMSBattery. You need to buy a LCD to go with it and a wheel-speed sensor.

 

[oleka]

<<<< A sinewave controller does make a big difference. Try the S06S from BMSBattery. You need to buy a LCD to go with it and a wheel-speed sensor. >>>>>

Can the S06S be used without LCD ?
As a power steering I'd like to use only regular thumb throttle.

 

[d8veh]

You have to use the LCD, but you don't have to connect the PAS. The PAS is very good. Why don't you want to use it?

 

[dogman dan]

Again, I seriously doubt you can fix the buzz with paint. Just put the motor back together. Further disassembly, if similar to the Mac motors, will require removing a lot of PITA spring clips. You'd need a set of spring clip pliers, then get in there and find paint doesn't really help much.

The sine wave controller should definitely smooth out the choppy PWM, quieting the motor some.

 

[oleka]

Are there any other sinewave controllers than S06S ?
I don't want to use LCD, too much gadgets for me ...

 

[Nobuo]

Are there any other sinewave controllers than S06S ?
I don't want to use LCD, too much gadgets for me ...

This for example it can be used without LCD as default

http://aliexpress.com/store/product...ler/937734_2029677362.html?spm=0.0.0.0.KmkZ9L

 

[oleka]

<<<This for example it can be used without LCD as default
<<<http://aliexpress.com/store/product/Electric-bike-sine-wave-controller-36V-250W-small-size-6-mosfet-controller-with-PAS-36v-controller/937734_2029677362.html?spm=0.0.0.0.KmkZ9L

Did you try it by yourself ?
Maybe someone else ?

 

[Ch00paKabrA]

I have the same issue with a small hub that I got from MW Motors. The motor has been working fine for 2 years but you have to just ignore the grunting. What is hard to understand is that if it is vibrations causing the grunting why does it just stop? Wouldn't it be logical for it to fade as motor speed increases? Mine gets louder and louder up to 10 mph then just stops.

Oleka, I received the same advice that you received here 2 years ago. I actually bought that controller and the motor still grunts. I have not noticed any decrease in the sound. Just an FYI.

 

[oleka]

Perhaps this noise is caused by a relatively low PWM frequency issued by the controller.
I think it is in the several kilohertz range where our ears are very sensitive.

Lets place another question:

Is there a 36V, 250...500W controller having PWM freq beyond 15...20 kHz ?

Sinewave output is not so important.

 

[riba2233]

All of them are over 15 kHz, so I doubt that that is the issue.

 

[oleka]

I changed my Persino chinese controller for another one, older Persino.
Now, motor is silent but max speed is lowered from 28km/h to 22 km/h.
Climbing power is good.
Connecting 2 cables limiting speed gives a limit of 12 km/h, which is a rather ridiculous value :-(

So the motor is OK, but these controllers are weird . . .