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Old Today, 02:47 PM
keffe1 is offline
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Deranged long range
Sweden, Uppsala County, Uppsala
Joined Aug 2013
588 Posts
I don't think it's right, what you write about the ESC. If you were right, the ESC would get hotter the less throttle that was applied. In my experience this is not the case. Rather the contrary actually. If I understand you right, you assume that the ESC dissipates the energy it does not pass on to the motor, in the form of heat. If this was the case, not only would it get hotter the less throttle was applied but throttle management would not affect flight times and that is simply not the case. Excuse me if I have somehow misunderstood you but this seems to be what you are saying and I'm pretty sure it's wrong.
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Old Today, 04:33 PM
dmanuel is online now
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They call me Spock
United States, TN, Knoxville
Joined Jun 2013
231 Posts
Listen to GlacierGirl

This concept has been discussed many times in the forums.
Check out post #2 in this thread:

http://www.rcgroups.com/forums/showthread.php?t=2478097

I have pasted an excerpt from the portion about ESCs.


For proof of concept, hook up a motor/prop combo that normally draws 40A to a 10A ESC and control the "load" on the ESC by holding throttle below the point that the watt meter reads say 8A. Let me know how long the ESC survives this test.
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Old Today, 10:13 PM
Glacier Girl is online now
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Kamikaze Ace
Glacier Girl's Avatar
USA, FL, Lakeland
Joined Jan 2010
2,894 Posts
Keffe, no you read it wrong, or my post confused you. YES, the esc does get hotter at lower throttle, because it's holding the power back. It has to hold what ever the motor is demanding, and that's the same no matter the throttle setting. It's how long it has to hold onto the power that causes it to heat up.

At low throttle it it's holding on to the power for a longer period of time between power on pulses, as the motor doesn't need the same frequency of them vs at full power.

So, say at full throttle the esc is on, on, on, off. At low throttle it's more like on, off ,off, off.
Each off cycle the FET's holding all that power back get hotter and hotter as there is less cooling off time before they get hit again.

That's why I suggest an over sized esc, more FET's to handle that heat, and even adding an additional heat sink to dissipate the heat. At lowest throttle we are pushing the limits of the esc's capabilities more so then at full throttle.
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Old Today, 10:24 PM
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Kamikaze Ace
Glacier Girl's Avatar
USA, FL, Lakeland
Joined Jan 2010
2,894 Posts
Whoops, and no it's not dissipating the power through heat, the FET's are holding it, and in doing so they get hot. Like a resistor does. The power is still there.

So yes dropping throttle will give you longer flight time. Back to the esc, as why.

Wide open gates/wide open throttle tends to let power flow through a lot faster (draining your pack faster) then if the gates are opening and closing off the flow and the opening part is a short period of time followed by a long time of the gate being closed. (throttle reduced)
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