Texas Instruments DRV8313 Evaluation Module DRV8313EVM DRV8313EVM データシート
製品コード
DRV8313EVM
Unsymmetrical
input
waveforms
Peaky current
Tuning the Motor With Proper Flux Threshold
A.1
Tuning the Motor With Proper Flux Threshold
As shown in
, the commutation instance is derived by integrating back-emf of non-energized
phase (obtain during each PWM on pulse) and comparing the integrated value to pre-defined threshold.
This threshold is in fact equivalent to flux of the motor because it is compared with integrated value of
back-emf. Value of flux threshold depends upon motor phase resistance, inductance and back-emf
constant; therefore this value needs to be tuned for the each different motor for commutation. For tuning
purpose usually oscilloscope is used to see the symmetry of the motor input voltages and/or motor phase
current. Please refer to the following scope-shots for the different flux threshold values.
This threshold is in fact equivalent to flux of the motor because it is compared with integrated value of
back-emf. Value of flux threshold depends upon motor phase resistance, inductance and back-emf
constant; therefore this value needs to be tuned for the each different motor for commutation. For tuning
purpose usually oscilloscope is used to see the symmetry of the motor input voltages and/or motor phase
current. Please refer to the following scope-shots for the different flux threshold values.
The scope-shots show the motor input voltage and a current waveform for one phase.
Figure 17. Typical Waveform for the HIGHER Flux Threshold
18
InstaSPIN-BLDC Implementation
SLVU815 – November 2012
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