DRM028 — Rev 0 Designer Reference Manual
MOTOROLA User Guide 109
Designer Reference Manual — Sensorless BLDC Motor Control
Section 6. User Guide6.1 Contents
6.2 Application Suitability Guide. . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.3 Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
6.4 Application Hardware and Software Configuration. . . . . . . . . 113
6.5 Software Parameters Setting and Tuning
for Customer Motor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126
6.2 Application Suitability Guide
This application suitability guide deals with issues which may be
encountered when tailoring application using customer motor.
6.2.1 Minimal Application Speed
As it is known, the back-EMF voltage is proportionally dependent on
motor speed. Since the sensorless back-EMF zero crossing sensing
technique is based on back-EMF voltage, it has some minimal speed
limitations! The motor start-up is solved by starting (back-EMF
acquisition) state, but minimal operation speed is limited.
The minimal speed depends on many factors of the motor and hardware
design, and differs for any application. This is because the back-EMF
zero crossing is disturbed and effected by the zero crossing comparator
threshold as explained below and in the sections 6.2.4.2 Effect of
Mutual Inductance and 6.2.4.1 Effect of Mutual Phase Capacitance .
NOTE: Usually, the minimal speed for reliable operation is from 7% to 20% of
the motor’s nominal speed.
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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