MATLAB Answers

Why does Simulink BLDC model block reports 1/10 of given Rotor-induced back emf

2 views (last 30 days)
KNeu
KNeu on 9 Sep 2020
Commented: KNeu on 6 Oct 2020
Using the ready-to-use model "BLDC_back_EMF" and entering a value of 9V for the property Rotor-induced back emf (settings tab Rotor) the scope block is reporting 0.9V peak-peak (1rpm, simulation time 1sec, input speed 2pi); this behaviour is consistent for possible units mV, V and kV) and independent of the number of pole-pairs which is correct.
Anything which i didn't understand?

  0 Comments

Sign in to comment.

Answers (1)

Joel Van Sickel
Joel Van Sickel on 10 Sep 2020
Hello KNeu,
the back EMF is dependent on motor speed. If you spin your motor faster, you will see the the output voltage increase. What value did you specify you for the back EMF measurement? In addition to that, back EMF is not the same as output voltage. You also have to take into account the current and impedance of the machine.
Regards,
Joel

  6 Comments

Show 3 older comments
Joel Van Sickel
Joel Van Sickel on 29 Sep 2020
Hello KNeu,
ok, you are running at 600 RPM, this means that it is at 10 Hz, or 10*2*pi rad/s. Your input speed is only 2pi rad/s which is 1/10 the rated speed, so it makes sense you are only seeing 1/10 the voltage.
Regards,
Joel
KNeu
KNeu on 6 Oct 2020
Hello Joel
clear. Didn't noticed that the value provided in the parameter Rotor speed used for back emf measurement links to the parameter Rotor-induced back emf. My fault.
KNeu
KNeu on 6 Oct 2020
to conclude :
back-emf constant ke = 9.6V/600rpm = 9.6V / (10*2*pi rad/s) = 0.1527 Vs
measured back-emf voltage E = omega * ke = 2*pi rad/s * 0.1527Vs = 0.96V

Sign in to comment.

Products


Release

R2020a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by