SPRACT7 August   2020 TMS320F280021 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C-Q1 , TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Fundamental Theories of FOC and Current Measurement
    1. 2.1 Basic Theory of FOC
    2. 2.2 Current Sensing Technique
      1. 2.2.1 Low-Side Current Measurement
        1. 2.2.1.1 Three-Shunt Current Sensing
        2. 2.2.1.2 Dual-Shunt Current Sensing
        3. 2.2.1.3 Single-Shunt Current Sensing
  5. 3Implementation of Single-Shunt Phase Current Reconstruction
    1. 3.1 Duty Cycle Compensation
    2. 3.2 PWM Phase Shift Compensation
    3. 3.3 Current Reconstruction
  6. 4Sensorless FOC With Single-Shunt Measurement
  7. 5Hardware Consideration for Single-Shunt Current Sensing
    1. 5.1 Slew Rate
    2. 5.2 Current Sensing Circuit
  8. 6Test Results
  9. 7Summary
  10. 8References

Abstract

The three-phase current sensing with only one dc link shunt resistor can be used for cost sensitive applications. However, special efforts need to reconstruct three-phase current from a dc link current. Moreover, phase current cannot be correctly measured from the single shunt when the active vector duration is less than the minimum measurement time. In order to get dc link current in unmeasurable vector area, a special algorithm for PWM compensation is required. This application report describes how to reconstruct three phase currents with a single current sensor in the inverter dc link. This solution is verified through InstaSPIN™-FOC with MotorControl SDK software platform.