Motorola M68HC08 manual Start-up Period, Maximal commutation period limit ∝s, Range -128,127

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

User Guide

Running state, or has a low start-up torque, DO decrease or increase the PER_CMT_START_US value. Table 6-2shows typical setting examples.

Must be:

PER_CMT_START_US<=PER_CMT_MAX_US/2

NOTE: Setting this constant is an empirical process. It is difficult to use a precise formula, because there are many factors involved which are difficult to obtain in the case of a real drive (motor and load mechanical inertia, motor electromechanical constants, and sometimes also the motor load). So they need to be set with a specific motor.

PER_CMT_START_US can be evaluated with PC master software tuning file tuning_bldc.pmp.

Table 6-2. Start-up Period

	Typical		First-to-Seco	Second-to-Thi
			nd	rd
Motor Size	PER_CMT_START_
			Commutation	Commutation
	US		Step Period	Step Period
Slow motor/high load and	8000.0	∝s	8 ms	8–16 ms
motor mechanical inertia
Fast motor/high load and	2000.0	∝s	2 ms	2–4 ms
motor mechanical inertia

Maximal commutation period limit [∝s]:

/* CAN_CHANGE_6_EXPER: */ #define PER_CMT_MAX_US 65536.0

Range: <0,65535*UNIT_PERIOD_T2_US>

Usually it is not recommended to change PER_CMT_MAX_US. The change is only necessary if the commutation period at start-up is to long.

Alignment to Start Increment of the regulators output [-]:

/* CAN_CHANGE_7_EXPER: */ #define START_INCR_OOUTREG 20.0

Range: <-128,127>

Designer Reference Manual		DRM028 — Rev 0
146	User Guide	MOTOROLA
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