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Author Topic: BRUSHLESS MOTOR RFI  (Read 479 times)

RHBAKER

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BRUSHLESS MOTOR RFI
« on: August 30, 2018, 10:31:42 PM »

  •   Am in the process of building a model of a fast patrol boat.
     The model uses two 2400 kV brushless motors controlled by individual 50A  ESCs; each motor drives one contra-rotating propeller. Each ESC is driven by its own Li-Po battery and operates within it's own individual electrical circuit. Both ESCs are driven from a common Rx, although use separate control channels. The Rx is separate battery, not BECC powered. The latest ESCs are fitted with small ferrite rings.
     For some time have been trying to resolve a “squeal” and “stutter” which can occur on motor start-up. Each motor powers up quietly and smoothy if operated by itself. If the motors are operated in unison a “squeal” and/ or stutter can occur with either motor. If the control lever is  returned to neutral and the motor stopped and restarted the problem may reoccur or the motor might start up cleanly.
     
  The vessel can be operated on either 2S or 3S power, on 3S the squeal and stutter is much more pronounced. Since starting the project have now replaced every drivetrain component, excluding the Tx & Rx, yet the problem persists. Those components have worked well on other vessels.
 Hope have explained the issue adequately. Question is, has anybody and idea what is causing the problem and, more importantly how can it be resolved?   

 
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grasshopper

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Re: BRUSHLESS MOTOR RFI
« Reply #1 on: August 31, 2018, 12:24:17 AM »

Is it possible that you have too many positive voltages from the three sources?


Run the Rx through the BEC from ESC1, disconnect the 5v supply from ESC2 to the Rx and ditch the separate Rx battery. It may be the supplies from three different sources causing a conflict



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RHBAKER

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Re: BRUSHLESS MOTOR RFI
« Reply #2 on: August 31, 2018, 12:38:51 AM »

Thanks for the response. Should have mentioned that the positive leads from both ESCs have been disconnected so the battery is the only power source.
Am sure it is some obscure item such as this though. Just need to find it!
 
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C-3PO

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Re: BRUSHLESS MOTOR RFI
« Reply #3 on: August 31, 2018, 08:43:04 AM »

Two pointers...

1.  Create a common ground connection - Tie all the negative (grounds) together for all components (Esc, Batteries,Receiver)

2. To further diagnose the problem use a Y splitter cable from one receiver channel to both ESC and see if you get the same squeal

C-3PO
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malcolmfrary

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Re: BRUSHLESS MOTOR RFI
« Reply #4 on: August 31, 2018, 08:49:50 AM »

What C-3PO said, add that the common ground connection might need to be heavier than originally thought.
ESCs only do what they are told, but a varying ground line potential can mess with their understanding of what they are being told, and if the two motors are not starting from the same position regarding the phases that are being generated, they might well produce noise rather than smooth motion.
It is very unlikely to be RFI, but there might be some overhearing between circuits, especially if the high power leads, motor or battery, run near to, and parallel to, any signal leads.
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steamboat66

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Re: BRUSHLESS MOTOR RFI
« Reply #5 on: August 31, 2018, 03:54:33 PM »

i have to say disregard the above, what you describe is a timing problem with the motors. you don't mention whether or not the motors are loaded. this squealing can easily happen with unloaded motors, but can happen loaded if the timing is not right between ESC and motor. 
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RHBAKER

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Re: BRUSHLESS MOTOR RFI
« Reply #6 on: August 31, 2018, 09:33:33 PM »

Thanks all for the ideas.
The squeal is most pronounced when running unloaded. Initially, when put into water it seemed to go away. It has now reoccurred, but much more loudly. Have also started blowing fuses on that ESC/Motor.
My current thinking is to go back through the system and make sure all the items suggested are implemented. I also need to check the motor programming as currently using the default settings.
Once have done all that, in a couple of weeks or so, will report back.
Thanks again and if anybody has any other suggestions, please let me know.
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SailorGreg

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Re: BRUSHLESS MOTOR RFI
« Reply #7 on: September 01, 2018, 08:11:28 AM »

I have an identical issue on a single motor, single ESC, bog standard setup, so I don't think it is anything to do with the dual motor arrangement.  As steamboat66 says, it appears to be a mismatch of some sort between the motor and ESC. I have tried two different ESCs and one is appreciably worse than the other as regards startup squeal. How to fix it? I don't know, but I will wait to see if someone else on here does!


Greg

RHBAKER

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Re: BRUSHLESS MOTOR RFI
« Reply #8 on: September 02, 2018, 04:01:33 PM »

Another development. My "squealing" motor suddenly started blowing fuses and then emitting little wisps of smoke from the motor internals. Guess it is in the process of failing.
Not sure if squealing is a precursor to failure, but am now trying to get another motor so can fit that.
Will update in due course.
If the motor was the reason all along, then being a dual layout or RFI interference were not the reasons 
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davem99

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Re: BRUSHLESS MOTOR RFI
« Reply #9 on: September 14, 2018, 11:58:11 AM »

I had a similar problem with a twin brushless Hovercraft. Recently acquired and worked OK but with some worrying squeaks etc from both motors. The drive motor failed first mainly I suspect because the ESC was Fwd/Rev with no delay. White then black smoke signalled the end. Replace Esc and motor and all OK.
The other motor was for the lift prop and made some loud squeaks and emitted wisps of smoke. Did arm but not like anything I was used to before. Decided that I really just needed an on/off control for this lift motor as it was on the same stick side as the rudder and had a spring, which meant I was always reducing power when moving the rudder if I was not concentrating.
This resulted in a cloud of black smoke and the motor was toast. ESC was OK and new motor fitted.
Not tried the switch and use no spring left stick for lift and right sticks for drive and steering.
As I had bought the model I had no knowledge of its previous use/misuse but I suspect the coil insulation had failed which would cause a timing problem (squeaks etc)as others have suggested.
Just a thought but I do route my signal and aerial wires as far away as possible from any high current power cables and this applies for all Radio Frequencies and types of motors.

Dave
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Dave

steamboat66

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Re: BRUSHLESS MOTOR RFI
« Reply #10 on: September 14, 2018, 03:54:28 PM »

totally agree on the rf, high current separation. this should never be in question, it should be the default setup.
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