AN1627 Freescale Semiconductor / Motorola, AN1627 Datasheet - Page 9

• Manufacturer Part Number: AN1627
• Description: Low Cost High Efficiency Sensorless Drive for Brushless dc Motor Using MC68HC (7)05MC4
• Manufacturer: Freescale Semiconductor / Motorola

value) as a parameter. The working point can be found for a certain load torque and PWM duty cycle. If
the load torque changes and the PWM duty cycle remains constant, the switching angle changes
accordingly. The zero crossing event is used to calculate the actual switching angle. Once it is known,
a corrective action can be made to keep the switching angle within the desired interval. This will allow
control of the motor at the best efficiency point without need of position sensors.
3
As was shortly introduced in the previous sections, the low-dynamic application is the field where this
drive can be used. The speed and load vary during a much longer time than the system mechanical time
constant.
The Table 3-1. summarizes the requirements of a typical (low-cost high-volume) application with
a Brushless DC motor.
AN1627
REV 0.2
Drive input characteristic:
Motor characteristic:
Load characteristic:
-30
USUAL REQUIREMENTS
Motor type:
-20
Freescale Semiconductor, Inc.
For More Information On This Product,
Figure 2-6.
-10
6 stator poles, three-phases, four
Go to: www.freescale.com
rotor poles, EC PM DC Motor
Input “inrush” max.:current
Max. acceleration time:
Max. electrical power:
(0 to rated speed)
Target efficiency:
The Average Motor Torque
Start-up torque
Min efficiency:
Torque range:
Speed range:
Fulfill European Community Regulation IEC555-1
0
Table 3-1.
Type
10
20
Max. 150% of nominal
10%-120% of nominal
0.8 over whole range
300-3000 RPM
Specifications
30
Varying
<300W
10sec
<30A
0.9
0.95
0.9
0.85
0.8
0.75
PWM
40
MOTOROLA
9