Update: Synchronous Rectification / Active Freewheeling is Awesome
adrian_sm said:
Bit of an update. I recently became aware of a cheap RC style ESC that has active freewheeling. Previously it was only high end (>$200) Kontrik & YGE ESCs that offered this, but now HobbyKing have a knock off of the YGE branded as a Hobbyking YEP for ~$50. The special thing about these controller is that it has Active Freewheeling or synchronous rectification, which means at partial throttle it uses the FETs rather than the diode to controll the flow of the collapsing current, meaning cooler ESCs. Woohoo. It also has anti-spark circuit which works by using a fet to connect the capacitors to the main supply slightly after power up. Nice. Here is a link that describes it more completely.
http://www.helifreak.com/showpost.php?p=4210229&postcount=3
Anyway I have ordered the
Hobbyking YEP 150A (2~6S) SBEC Brushless Speed Controller
Well the results are in, and they are astounding. With a big difference in partial throttle performance.
I have tested a huge number of different controllers, but just pulled out three for comparison.
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$120 - Castle Creation Pheonix ICE 100
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$50 - Hobbyking YEP 150A ESC
- typical 6fet EB306 XieChang ebike controller, built from ecrazyman no-fet controller kit, populated by me with genuine
IRFB3006pbf fets (Rdson = 2.1mOhm)
The test procedure was to run the same motor, against the same dyno load, at the same voltage, and see what the controller temperature did for various throttle settings.
100% = Full throttle, ~1.25Nm load
95% = decrease throttle until the speed drops slightly to introduce switching losses, ~1.2Nm
50% = drop the throttle until speed is half of the 100% throttle speed, ~1.35Nm.
For the EB306 ebike controller I just ran it at 50% from the start. Sorry.
Here is the graph.
This is a clear win for the YEP, rising to only 40 degC above ambient, when I had to aborted the CC ICE 100 run when the temp hit 100 deg-C, looking to stabilise at +100 degC above ambient
Even at full throttle the YEP with a token heatsink outperformed the CC ICE 100, with aluminium fins everywhere.
The EB306 tricked out with expensive fets faired okay but, even with a huge thermal mass and the large heatsink of a case, was rising in temperature twice as fast as the YEP, and looked like it would stabilise at somewhere around +60degC above ambient.
Conclusion
Controllers with synchronous rectification, or active freewheeling absolutely rock for conditions where the controller has to limit current due to partial input throttle or hitting the current limit.
Now the question is what controllers have it, and which is best for my needs. The ones I am aware of are:
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Hobbyking YEP controllers
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YGE (Young Generation Electronics) controllers
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Kontronik
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Kelly Controllers
-
emsiso eDrive controllers
The Hobbyking YEP controllers are handsdown the most affordable and cost effective of these, and the most suited to my needs.
- Adrian