Source Code Implementation for Induction Motor Scalar Control

Induction Motor Scalar Control Technical Implementation

Scalar control, commonly known as V/f (Voltage-to-Frequency) control, represents a fundamental motor drive technique that maintains a constant voltage-to-frequency ratio to regulate induction motor speed without requiring position sensors or complex feedback systems. Implementation typically involves generating PWM signals through microcontroller code that linearly correlates output voltage with frequency.

Core Algorithm Principles The primary algorithm maintains a constant V/f ratio by programming voltage and frequency relationships in the control software. Key implementation steps include: - Frequency command processing with ramp-up/ramp-down rate limiting - Voltage calculation using V = k×f + compensation (where k is the V/f ratio constant) - Low-frequency voltage boost compensation to counteract stator IR drop Code implementation often uses lookup tables or mathematical functions to define the V/f profile characteristics.

Key Implementation Components Voltage Source Inverter (VSI) Control - Implemented through Space Vector PWM (SVPWM) or sinusoidal PWM algorithms in DSP/microcontroller code V/f Profile Programming - Defined in software as piecewise linear functions or curved profiles with parameters: Base frequency (typically 50/60 Hz) Minimum frequency (for start-up) Voltage boost settings for low-speed operation Open-Loop Speed Control Algorithm - Calculates output frequency based on speed reference without feedback, using code structures like: frequency_reference = speed_command × pole_pairs / 120

Software Implementation Advantages Simplified code structure compared to vector control algorithms Reduced processor requirements enabling cost-effective microcontroller solutions Sensorless operation eliminates encoder interface code and hardware costs Stable performance in constant torque and constant power regions

Algorithm Limitations Limited dynamic response due to open-loop structure - cannot instantaneously compensate for load changes Torque production accuracy decreases at low speeds without slip compensation algorithms Requires additional code for starting torque enhancement and slip compensation

Practical Applications and Code Examples Industrial drive systems using PLCs or embedded processors MATLAB/Simulink implementations with V/f control blocks and PWM generation C-code examples for DSP platforms featuring: Frequency ramp functions Voltage compensation algorithms Protection routines (overcurrent, overvoltage)

Would you like detailed code examples for specific implementation aspects such as PWM generation, V/f profile customization, or low-speed torque enhancement algorithms?