Motorola M68HC08 manual User Guide, Application Suitability Guide, Minimal Application Speed

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Designer Reference Manual — Sensorless BLDC Motor Control

Section 6. User Guide

6.1 Contents

6.2 Application Suitability Guide . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.3 Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

6.4 Application Hardware and Software Configuration . . . . . . . . . 113

6.5Software 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.
DRM028 — Rev 0		Designer Reference Manual
MOTOROLA	User Guide	109
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