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450 Class Electric Helicopters 450 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar. |
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09-10-2011, 05:47 AM | #1 (permalink) |
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Join Date: Jul 2011
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Motor and PWM frequency
I recently bought a Turnigy AE-45A. In the manual, it is said that setting the PWM to 24khz (default 12khz) may allow high KV motor to run more smoothly. I tried it because the motor is a 4000Kv. The first thing I noticed is that the motor starts spinning more smoothly, while spooling up, and the overall sound also.
So this afternoon I flying at the park. I am not sure but it seemed that I had a much longer flight. Perhaps 15 min. Is that motor more efficient now or is it just me thinking it? |
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09-10-2011, 08:00 AM | #2 (permalink) |
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Join Date: Jun 2008
Location: Trondheim Norway
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Its not onely you.
You can increase/decrease motor effisiancy bye changing the PWM frequency depending on motor specks, and if your motorspesification says 24Khz then the motor will work best at that frequenzy. In comparison the Scorpions work best at 8Khz and are part of the motor spesifications.
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09-10-2011, 06:11 PM | #3 (permalink) | |
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Join Date: Aug 2010
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Quote:
Why Scorpion says 8kHz is unknown to me. It doesn't make any sense. There is no difference physics for Scorpion and every other motor. I have an opinion of course !, and that is all ESC's work better at lower PWM frequencies, mainly because they tend to run hotter the more transitions the FET's make- when the FET's transit between off (~infinite resistance) and on (very low resistance), they do pass through a region of finite resistance, and this makes heat. The more transits they make, the hotter the ESC gets. So while the motor is happier, the ESC isn't. Usually the only instructions you get are from the ESC manufacturers---Scorpion included-so recommendations are usually for lower PWM frequencies. So that's my guess, it is easier on the Scorpion ESC's (other ESC's too of course). But system wide, the higher PWM saves you a bit of power. In my test it was about 5%, not a gigantic amount. |
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09-10-2011, 06:49 PM | #4 (permalink) |
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Join Date: Aug 2010
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That is not correct. Motors will have a different inductance (based on a lot of things related to construction/winding). Similarly, motors have varied pole counts and operational RPM. So, you have certain parameter boundaries with PWM (i.e. you would not want your PWM lower than your commutation rate).
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09-15-2011, 04:23 PM | #5 (permalink) |
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Join Date: Dec 2006
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i have a scorpion commander 45a v3 esc. I need to change the switching frequency to 16khz. Is there a way to do that. I am using a funcopter direct drive motor and it needs 16khz. thanks
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09-16-2011, 12:18 AM | #6 (permalink) |
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Steve, I FINALLY got my package from The King which includes the same Turnigy 45a ESC. Im going to play with the timing and kHz as well and see what temps / flight times I get. (Running an Exceed Alpha 400 motor)
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ae-45a, trex 450, turnigy |
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