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What is the maximum allowed PWM duty cycle when using six-step firmware library

Question asked by VanderMey.Tim on Mar 20, 2017

I have a sensorless BLDC drive application where I need to get near 100% duty cycle on the power PWM while spinning at about 1300Hz (21 pole pairs, 3700RPM).  However it appears that the six-step library only samples the BEMF during the off time, thus precluding the use of 100% duty cycle on the PWM.  Here are my questions.


1) How much off time is required to sense the BEMF? Or how close to 100% duty cycle can I get using this method?

2) Do you have another library I can use that does not have this duty cycle limitation?

3) I don't need FOC, but if it would work in my application I am open to it.  Would your FOC library run at 1300Hz or faster with a low inductance motor?