Three-Phase Motor Vector Control for Accurate Idling Detection
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Solution Overview
Problem
Existing motor control devices struggle to accurately determine if a three-phase motor is in a no-load operation state, especially when the power supply voltage is high, as the measured current value can fall below the threshold even when the motor is not idling, leading to incorrect identification of no-load conditions.
Innovation Solution
A motor control device and method that execute vector control on a three-phase motor using a current detection unit to convert three-phase currents into two-phase currents, with a determination unit identifying idling based on a q axis current value equal to or smaller than a set threshold, independent of power supply voltage, and adjusting the determination threshold according to the motor's rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power supply voltage is increased to reduce power supply current, then energy efficiency is improved, but measurement precision of current detection deteriorates
Solution Approach 1:
The patent changes the parameter used for no-load determination from absolute current value to q-axis current value obtained through coordinate transformation. This parameter transformation allows accurate no-load detection independent of power supply voltage, resolving the contradiction between energy efficiency improvement and measurement precision deterioration.
Solution Approach 2:
The patent introduces the q-axis current value as an intermediary parameter that mediates between the measured current and the no-load determination. By using this intermediate transformed parameter, the system achieves accurate no-load detection without being affected by variations in power supply voltage.
2Loss of energy
If power supply voltage is increased to reduce power supply current, then energy consumption is reduced, but reliability of no-load determination deteriorates
Solution Approach 1:
The patent transforms the current parameter from three-phase stationary coordinates to two-phase rotating coordinates, extracting the q-axis current component as the reliable indicator for no-load determination. This parameter transformation ensures reliable no-load detection across different power supply voltage conditions while maintaining energy efficiency.
3Measurement precision
If three-phase current is converted to two-phase current to extract q-axis current value, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent utilizes the existing vector control calculation framework to perform the three-phase to two-phase transformation and q-axis current extraction. By integrating the no-load detection function into the existing control calculations, the system achieves precise detection without adding separate dedicated hardware or complex processing units.
Solution Approach 2:
The patent merges the no-load detection function with the existing vector control current calculation process. The q-axis current value, already computed for motor control, is simultaneously used for no-load determination, combining multiple functions into a unified processing approach that avoids additional complexity.
4Reliability
If q-axis current value is used for no-load determination, then reliability is improved, but processing load increases
Solution Approach 1:
The patent makes the existing vector control calculations serve dual purposes: both motor control and no-load determination. The q-axis current value computed for torque control is simultaneously used as the basis for no-load detection, achieving reliable determination without additional processing burden.
Data Source
AI summary
A motor control device is configured to execute vector control on driving of a three-phase motor according to a d axis current command and a q axis current command. The motor control device includes: a current detection unit configured to detect a current to be input to the three-phase motor; and a control unit configured to control driving of the three-phase motor. The control unit includes: a three-phase to two-phase conversion unit configured to acquire a q axis current value by converting a three-phase current input to the three-phase motor and detected by the current detection unit into a two-phase current; and a determination unit configured to determine that the three-phase motor is idling when the q axis current value is equal to or smaller than a determination threshold set in advance.