DSCs Enable Field-Oriented Control for Washer Motors
by Jorge Zambada, Applications Engineer, Digital Signal Controller Division, Microchip Technology, Chandler, Ariz., Power Electronics Technology, Mar 01 2007
Focus:
Appliances such as washing machines that use permanent magnet synchronous motors (PMSMs) can benefit from field-oriented control (FOC) because it requires no position sensors. (This advantage is handy when the motor is immersed in oil, which precludes the use of position or speed sensors.) Proprietary ICs implement FOC; however, new digital signal controllers (DSCs) can provide an economical alternative. In addition to running the FOC algorithm, DSCs integrate the needed motor-control peripherals. This article describes the FOC motor-control firmware and development tools created by Microchip Technology; provides a detailed summary of the FOC (vector-control) algorithm; describes a current observer model that permits indirect measurement of the motor's back EMF; explains how motor current and back EMF are calculated and how phase compensation and the motor startup subroutine work; and describes the FOC algorithm in terms of a software state machine. Advantages of DSC-based FOC control are also discussed.
What you’ll learn:
- How to implement field-oriented control of permanent magnet synchronous motors using digital signal controllers (DSCs)
- How to understand operation of a field-oriented control (vector control) algorithm
- How to understand the advantages of using digital signal controllers to implement field-oriented control of permanent magnet synchronous motors
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