Motor Demagnetization Diagnosis Using Rotor-Phase-Corrected Pulse Timing
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Solution Overview
Problem
Existing demagnetization diagnosis methods for motors suffer from inaccuracies due to phase position errors of the permanent magnet rotor, leading to suppressed accuracy in demagnetization detection.
Innovation Solution
A demagnetization diagnosis device that includes a power converter, a motor with specific windings, a pulse voltage generator that calculates a corrected pulse voltage application time period based on the rotor phase difference, and a demagnetization determiner that uses measured currents to determine demagnetization, ensuring accurate diagnosis by selecting the nearest voltage vector and adjusting the pulse duration accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a d-axis pulse voltage is applied for a predetermined fixed time period during motor stop, then demagnetization diagnosis can be performed, but the diagnosis accuracy is suppressed due to phase position errors of the permanent magnet rotor
Solution Approach 1:
The patent applies dynamics by making the pulse voltage application time period variable rather than fixed. The control device calculates a corrected pulse voltage application time period based on the rotor phase position, allowing the diagnosis method to adapt dynamically to different rotor phases. This resolves the contradiction by enabling accurate demagnetization diagnosis across all rotor phase conditions while maintaining the simplicity of the fixed-time-period approach when applicable.
Solution Approach 2:
The patent changes the parameter of pulse voltage application time period from a fixed value to a corrected value that varies with rotor phase position. By calculating the corrected time period using the rotor phase information, the system optimizes the diagnosis accuracy for each specific rotor phase condition, thereby improving measurement precision without compromising reliability across different operating conditions.
2Ease of manufacture
If a fixed pulse voltage application time period is used, then the diagnosis method is simple to implement, but errors occur in d-axis current value depending on rotor phase position
Solution Approach 1:
The patent modifies the pulse voltage application time period parameter from a fixed value to a corrected value that incorporates rotor phase position information. This allows the system to maintain implementation simplicity while eliminating the d-axis current value errors that occur with fixed time periods under varying rotor phase conditions.
Solution Approach 2:
The patent implements feedback by using the measured rotor phase position to calculate and adjust the pulse voltage application time period. This feedback mechanism ensures that the diagnosis method automatically compensates for rotor phase variations, maintaining high measurement precision without significantly increasing implementation complexity.
3Measurement precision
If the pulse voltage application time period is corrected based on rotor phase difference, then demagnetization diagnosis accuracy is improved, but the device complexity increases due to additional calculations and measurements
Solution Approach 1:
The patent applies universality by making the existing control device perform multiple functions: it not only controls the motor but also measures rotor phase position and calculates the corrected pulse voltage application time period for demagnetization diagnosis. This multi-functionality approach improves diagnosis accuracy without requiring separate dedicated hardware, thereby limiting the increase in device complexity.
Solution Approach 2:
The control device serves itself by utilizing its own existing measurement capabilities and control functions to perform the demagnetization diagnosis. By using the rotor phase position information already available for motor control and the existing pulse voltage application capability, the system achieves improved diagnosis accuracy without adding significant external complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves the accuracy of demagnetization diagnosis by correcting pulse voltage application time periods and using precise current measurements, effectively addressing phase position errors and enhancing the detection of demagnetization in motors.
Implementation Method 1
a pulse voltage generator that calculates a corrected pulse voltage application time period... and outputs the selected voltage vector as a voltage vector command
Implementation Method 2
a current measurement instrument that measures output currents of three phases of the power converter outputted
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A pulse voltage generator 7 calculates a corrected pulse voltage application time Ton'. The pulse voltage generator 7 also outputs, for the duration of the corrected pulse voltage application time Ton', a voltage vector closest to a rotor phase γ from among voltage vectors V1 - V12 as a voltage vector command V+∗. A current detector 8 detects the three-phase output currents Iu, Iv, Iw of a power converter 3, which are obtained when the first to sixth switching elements of the power converter 3 are turned on and off on the basis of the voltage vector command V+∗. A three-phase/two-phase converter 9 converts the three-phase output currents Iu, Iv, Iw to two-phase output currents to output d-axis current Id. When the d-axis current Id after the corrected pulse voltage application time Ton' has elapsed becomes less than or equal to a demagnetization determination threshold value, a demagnetization determiner 10 determines that demagnetization occurs in a permanent magnet of the rotor of a motor 4. This improves the accuracy of a demagnetization diagnosis in a demagnetization diagnosis device for a motor.