Coreless motor PWM settings - RC Groups
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Nov 05, 2017, 04:16 PM
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Coreless motor PWM settings


Hi,

Trying to id and solve a hot motor issue. If it is an issue.

I built a 75 mm brushed quad using parts from BetaFPV.

I used 7x20 mm 17500 KV coreless brushed motors, F3 brushed FC with OSD and Spektrum receiver, and BetFPV's 75mm whoop frame with 3 bladed props. The motors get pretty hot after a 3min flight, i.e. Holding you fingers on them is uncomfortable.
My PIDs are as follows:
Roll P 44, I17, D9
pitch P58, I21, D14
Yaw P70, I45
Motor PWM frequency is 16000

I've lowered the roll and pitch I and D values a bit and the motors seem a bit cooler. I am wondering if the PWM setting might need changing as I think the FC was originally set up for 7x16 mm motors but still 175000 kv. Not sue how long these motors are going to last getting this hot and would like to maximise their lifecycle. Is this heat actually normal for this setup? I've got a lizard95 with brushless motors and they are barely warm after a 4 min flight.
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Nov 06, 2017, 04:42 PM
The Denying Dutchman
Denying Dutchman's Avatar
PWM is nothing more than the switching frequency on which your motors get their juice to operate, that value can be as low as a few hundred hertz up until several kHz. If your motors are getting too hot, which they are, it's more likely that the load is too high or the voltage. Or both.
Nov 07, 2017, 03:29 AM
Registered User
Quote:
Originally Posted by Denying Dutchman
PWM is nothing more than the switching frequency on which your motors get their juice to operate, that value can be as low as a few hundred hertz up until several kHz. If your motors are getting too hot, which they are, it's more likely that the load is too high or the voltage. Or both.
Ok thanks, I'm using the recommended voltage on the motors. The lipos are 3.7 volt 450mah 1s. They weigh about 14 g. The quad weight with bat is about 46g. These are higher powered bigger motors which seemed to be best for the build. I'll try a smaller battery but I'm only getting 3mins of flight time so didn't think it would be load or voltage. I'll try messing aroung with the CG on the frame also to see if that helps


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