AN1913D Freescale Semiconductor / Motorola, AN1913D Datasheet - Page 4

• Manufacturer Part Number: AN1913D
• Description: 3-phase BLDC Motor Control with Sensorless Back-EMF ADC Zero Crossing Detection using DSP 56F80x
• Manufacturer: Freescale Semiconductor / Motorola

Target Motor Theory
4
.
The motor can have more then just one pole-pair per phase. The pole-pair per phase defines the ratio
between the electrical revolution and the mechanical revolution. For example, the shown BLDC motor
has three pole-pairs per phase; which represents the three electrical revolutions per one mechanical
revolution.
The rectangular, easy to create, shape of applied voltage ensures the simplicity of control and drive.
However, the rotor position must be known at certain angles in order to align the applied voltage with
the Back-EMF. The alignment between Back-EMF and commutation events is very important. At this
condition the motor behaves as a DC motor and runs at the best working point. Thus, simplicity of
control and performance makes the BLDC motor the best choice for low-cost and high-efficiency
applications.
BLDC control with BEMF Zero Crossing using ADC
Freescale Semiconductor, Inc.
Figure 3-2. Three Phase Voltage System
Figure 3-1. BLDC Motor - Cross Section
For More Information On This Product,
Go to: www.freescale.com
Stator
Stator winding
(in slots)
Shaft
Rotor
Air gap
Permanent magnets
electrical
angle