Synchronous Rectification + High PWM rate = GOOD
Check out the temperature rise for the ESC under the same load conditions, but at different PWM rates. 8 vs 16 kHz.
16 kHz is a hands down winner at the lower speeds.
ESC:
HiModel 150Amp ICE
- 18 deg timing
- synchronous rectification = ON
Horizontal axis is RPM.
Green lines shows the torque load [N.m] applied by my light bulb load bank
Blue line is the 8kHz PWM
Red line is the 16kHz
The temperatures are the predicted equilibrium temp above ambient, based on ~12 min of constant load, then extrapolation.
Observations:
- the higher PWM rate is keeping the phase currents in check since the inductance is doing a lazy job of it once the BEMF drops off.
- due to the synchronous rectification the switching losses are not that bad, so the higher switching frequency does not lead to a lot of extra waste heat on its own.