Start-Up Period - Motorola M68HC08 Reference Manual

User Guide
NOTE:
Designer Reference Manual
146
Freescale Semiconductor, Inc.
Running state, or has a low start-up torque, DO decrease or increase
the PER_CMT_START_US value.
examples.
Must be:
PER_CMT_START_US<=PER_CMT_MAX_US/2
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.
Motor Size
Slow motor/high load and
motor mechanical inertia
Fast motor/high load and
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>
User Guide
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Table 6-2
Table 6-2. Start-up Period
Typical
PER_CMT_START_
US
8000.0 s
2000.0 s
shows typical setting
First-to-Seco Second-to-Thi
nd rd
Commutation Commutation
Step Period Step Period
8 ms 8–16 ms
2 ms 2–4 ms
DRM028 — Rev 0
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