I am currently writing my bachelor’s degree for “BLDC motor and controller” and I’m just bringing out couple of theories and hypothesis’ to see if they make sense to you guys.
1st topic/theory: “Effective” voltage and torque
What is effective voltage? Effective voltage is the “voltage doing work” in the motor’s windings and is the difference between the PWM cycled battery voltage and the motor’s BEMF voltage. If the PWM battery voltage is the same as the BEMF voltage, no current flows and no torque is generated.
Example with arbitrary values: 12 V battery voltage and 50 % PWM duty cycle -> 6 V Motor’s BEMF voltage -> 4 V “Effective voltage” = 6 V - 4 V = 2 V
Question: Does the effective voltage linearly effect the current/torque? AKA using the example values above. The 2 V “effective voltage” would cause current X, to flow through the winding. Now, if the motor’s BEMF is just 2 Volts, the “effective voltage” would now be 4 Volts, would the resulting current now be 2X?
2nd topic/theory: Offset of “Effective” voltage and behavior
How does the current behave when we offset the “effective voltage” and BEMF voltage?
Example with arbitrary values: Our “effective voltage” -> 2 V 1st case voltages -> PWM 4 V, BEMF 2 V 2nd case voltages -> PWM 12 V, BEMF 10 V
Question: Is the same current flowing the same in both cases? Both cases have the same “effective voltage”, but is the current the same too? Or is the current effected something else also that is derived from those 2 voltages (Test conditions are theoretical and therefore ideal, no friction losses or hysteresis losses etc…)?
Please stay on topic and avoid digressing. Or at least point out that you’re going off-topic like below
Offtopic. I have gathered a bunch of student candidates from my local university who we’re interested in my electric longboard project. I am in the process of interviewing them. I made a presentation in which I showed the board, it’s specs and how it was developed and presented three bachelor’s degree eligible works for the group of 14 students. Out of the 14 students I got five interested students who wanted to join in. I have 3 areas available (BMS, Remote and smartphone app), so I’ll have to interview the five and pick one to each area. We’ll see how it progresses from here.