The duty cycle limit (95%) is present to:
- ensure charging of the high side gate driver power supply capacitor,
- allow phase current measurement during null vectors, a certain duration is needed to avoid switching noise in the measured current
The capacitor anyway get charged at least once for each electric revolution even at 100% duty cycle and max over-modulation. So the duty cycle limit should only be needed at low RPM. This raises the question: How often does the high side capacitor need to be charged? (What i "low" RPM?)
The current measurement can be moved to other vectors than the null vectors -- VESC-6 has inline phase shunts, so it can be done in any vector -- in particular it can be moved dynamically to the vectors with longer duration.
If I understand the duty cycle limit correctly; it comes into action twice per PWM cycle -- 5% during V0 and 5% during V7 -- so removing this limit would give 11% higher voltage to the motor = 11% higher RPM, . Adding over-modulation (removing the circle limit) can add another 11% or so.
Who wants 22% more power?
Hello. I wonder if you can help me. I AM A NEWBEE IN vesc.
I have converted car alternator running both in FOC and BLDC fine. But there is a rpm limit at about 37000erpm. Battery is 16s 67v.
As i calculated , the motor can handle 10000rpm. So i want to run 80000erpm ,as i have 8 polepairs.
What settings should i tweak to achieve this?
Silent Revolution is NOW !
If the KV value of the motor is too low, you will have a hard time to drive it faster. Field weakening will make it spin faster, but it has the downside that you inject additional currents and generate additional losses and heat.