Hi I am using slightly edited model example "BLDC Speed control" (Three-winding brushless DC motor with trapezoidal flux distribution). I am using 3 phase wye wound BLDC motor. I will be using motor control where all phase-to-phase voltages must be known.
I suppose when BLDC motor is connected to 3 phase inverter and lets say phase A is connectet to + and B -. Current is passing throught two winding which have same resistance, self inductance, mutual inductance (and lets say stator inductance fluctation will be 0), back emf is e_a = -e_b so I suppose that at neutral point of motor we will have half of DC voltage. So |ua| - |ub| = 0.
When I try to check it in matlab simulink, difference is zero only in part of waveform - wafeforms in attachments.
In block BLDC motor there is defalut value for "Rotor angle over which back emf is constant" pi/2*p, where p is pole pairs, but for 1 pole pair motor it is 90°, and from image above it takes 120°, is defalut value in example wrong? Why there is no zero difference between |ua| - |ub| during this entire commutation step (except demagnetization)? (In BLDC block I have Stator inductance fluctuation, Lm: set to 0.)
Model in attachements (r2020b).
Description for BLDC simulink block is here: https://www.mathworks.com/help/physmod/sps/ref/bldc.html
Literature link: https://journals.sagepub.com/doi/pdf/10.1177/0020294019842607
Literature link 2: https://www.researchgate.net/publication/339563069_Sensor_less_Speed_Control_Method_for_Brushless_DC_Motors_Using_Back_EMF_Method