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July 2007 Rev 3 1/102
AN1904
Application note
ST7MC three-phase AC induction motor control
software library
Introduction
This Application Note describes a 3-phase induction motor control software library
developed for the ST7MC. This 8-bit microcontroller contains a peripheral dedicated to 3-
phase brushless motor control, making it suitable for AC induction motors and permanent
magnet DC/AC motors (PMDC/PMAC also called BLDC).
The library described here is made of several C modules that contain a set of convenient
functions for the scalar control of AC induction motors and is compatible with COSMIC
(www.cosmic-software.com) and METROWERKS (www.metrowerks.com) compilers. The
control of a Permanent magnet motor in Six-step mode is detailed in application note
AN1905. The control of a PMAC motor in Sine wave mode with sensors is detailed in
application note AN1947.
This software allows users to quickly evaluate both the MCU and the available tools, and to
have a motor running in a very short time when used together with the ST7MC starter kit
(ST7MC-KIT/BLDC) and the demonstration AC motor (ST7MC-MOT/IND). It also eliminates
the need for time consuming development of sine wave generation and speed regulation
algorithms by providing ready-to-use functions that let the user concentrate on his
application layer.
The prerequisite for using this library is the basic knowledge of C programming, AC motor
drives and power inverter hardware. In-depth know-how of ST7MC functions is only required
for customizing existing modules and when adding new ones (grey modules in Figure 1) for
a complete application development.
Figure 1. Overall software architecture
PWMART PORTS
ADC
SCI
16-bit
MTC SPI
MCO[0..5]
Emergency Stop input
Speed feedback
AC MOTOR DRIVE
3-PHASE SINE WAVE GENERATION
SLIP
COMMUNICATION
PROTOCOL
REGULATION
APPLICATION LAYER
WWDG
Timer
PWM outputs
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