I'm building a new copter with U7-490 using FF ESCs running 6s. These controllers have a switchable PWM frequency from 8KHz to 12KHz. I emailed Tiger and was informed that 8KHz is recommended with the U7-490. FF controllers by default are set at 12KHz. So for anyone running this setup you may want to change your controller's operating frequency.
Hey Howard, I've been on outrunner mode, was fine for winter but not for summer. Going to try the 8khz. What is your timing set to?
So Ms Google suggests a formula for deterring the appropriate PWM frequency that goes something like: (Motor KV x Nominal Voltage x Pole Count) / 20 = PWM frequency So 490 x 22.5 x 14 /20 = 7715 which rounds out to 8Khz But this makes me wonder how correct this approach is ....because it would put the old MT3515 400 that I was running down at 6kHz and the using the FF ESC at 12KHz ... did this cause problems ???
Thanks Chris, I found that exact forumla and set up my esc's today at 8 kHz just wondering what timing people are using ?
Interesting find, Chris. As you say, it looks a bit wobbly for the MT3515. On a related note, I've still not persuaded Ms Google to tell me what the relationship is between a given motor geometry and the timing/phase angle of the ESC should be....the relationship seems more be folklore and ratification of rumor as far as I can tell. "Try 25 degrees and if the motor and/or ESC doesn't catch fire, then you got the right number." Andy.
I suspect that if the motors and ESCs are running in that 40-50% hover throttle range, then the timing and refresh rates do not matter to much, but when you are pushing them to run a bit harder it gets more critical or flakey ... depending on gravity Most references I found for refresh rates and motor timing where all talking about the audible frequency ranges for ESCs in consumer electronics .... and that was pretty much just change the refresh rate so that it is outside the audible spectrum ... different groups/different focus..
Well Ms Google didn't deliver a formula for esc timing, but quite a good article, which made sense to me .... Or maybe more confused http://www.theampeer.org/timing/timing.htm From that it looks like the adjusting the timing advance depends on how hard your system is working, a motor operating the majority of the time at a 50% throttle should have a low timing advance, and if your planing to run the motor flat out most of the time then the timing advance should be greater. So it comes back to how much you are trying to lift and do you have the right size motors and props. Drag racing in cars and boats, crank the advance up (and cross fingers) .... Multirotors, leave the time low and make sure the motor/prop combination is right for the all up weight. At least that's my take away from it ... In would like to hear other views on it... Cheers Chris
Sorry about all the typos ... Posting from the phone ... (Who would have thought that was possible 20yrs ago)