Abstract
Problem statement: This study described the design of a 3-phase AC Induction Motor (ACIM) vector control drive with position encoder coupled to the motor shaft. Approach: It was based on free scale's (Motorola's) 68k micro processor devices. Although the free scale 56F80x (56800 core) and 56F8300 (56800E core) families were well-suited for digital motor control and offer all things was needed, but we decided to realize a complete vector controller with a powerful 68k processor. Results: Obviously all 680X0 and many 683XX can overcome this task very easily, but we decided 68332 for time consuming because it combines high-performance data manipulation capabilities with powerful peripheral subsystems. All software and hardware was based on Peter J. Pinewski's nice research from Motorola. Conclusion: In this study the overall software algorithm and in two fellow papers the hardware schematics and performance will be described respectively.
Highlights
By mapping the measured three phase stator currents as a vector onto a two axis (d-q) coordinateTraditional control methods, such as the VoltsHertz control method, control the frequency and amplitude of the motor drive voltage
The rotor current cannot be measured because the rotor is a steel cage and there are no direct electrical connections
If the correct value of Lr/Rr is not known or is not achieved the vector control algorithm will operate in a “de-tuned” manner. This means that the flux and torque currents are improperly aligned with the rotor flux and that they are not truly de-coupled
Summary
By mapping the measured three phase stator currents as a vector onto a two axis (d-q) coordinate. From a practical point of view, the flux and torque currents are controlled through the motor voltages and slip frequency How these are controlled is based on calculations made on the measured phase currents and speed. If the correct value of Lr/Rr is not known or is not achieved the vector control algorithm will operate in a “de-tuned” manner This means that the flux and torque currents are improperly aligned with the rotor flux and that they are not truly de-coupled. The software must convert the unipolar A/D readings into positive and negative values fr rpm × p 120 for use in the algorithm This requires a simple (2) subtraction of the zero current reading from the present phase current reading. This is important for formatting the data into signed fractional numbers
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