Permanent Magnet Synchronous Motor Constant Calculation via Composite Voltage
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Solution Overview
Problem
Existing methods for calculating the motor constant of permanent magnet type synchronous motors are time-consuming and prone to errors, especially when measuring inductance, and require multiple test signals, which can lead to inaccurate results and are influenced by the motor's current value.
Innovation Solution
A method involving applying a composite voltage with a DC and AC component, varying the AC frequency, detecting the motor current, calculating the phase difference between the AC components of the voltage and current, and calculating the motor constant when the phase difference is nearly 45 degrees, allowing for accurate calculation without the need for constant DC currents or multiple test signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If different test signals are used for measuring resistance and inductance, then both parameters can be obtained, but measurement time increases
Solution Approach 1:
The patent combines resistance measurement and inductance measurement into a single test signal application process. By using a composite test signal containing both DC and AC components simultaneously, both parameters are measured in one operation rather than requiring separate measurement procedures, thus reducing total measurement time while maintaining measurement precision.
Solution Approach 2:
The measurement process continuously acquires both resistance and inductance data during a single sustained test signal application. The system maintains continuous measurement of both parameters throughout the test duration, eliminating idle time between separate measurements and ensuring uninterrupted data collection for both electrical characteristics.
2Measurement precision
If DC current is applied to obtain coil wire resistance, then resistance can be calculated, but measurement time increases due to waiting for current to become constant
Solution Approach 1:
The patent applies the DC component of the test signal in advance along with the AC component, rather than waiting for DC current to stabilize separately. By establishing the DC current path simultaneously with AC current application, the system eliminates the waiting period for current stabilization while still obtaining accurate resistance measurements from the DC voltage-current relationship.
Solution Approach 2:
The system applies a composite test signal with both DC and AC components at full amplitude simultaneously, rather than applying DC current at reduced levels or waiting for partial stabilization. This excessive action of applying both components at full strength from the start accelerates the measurement process while the calculation method compensates to maintain accuracy.
3Measurement precision
If AC current frequency is not properly set for inductance measurement, then detection accuracy of phase difference degrades, but determining proper frequency requires additional time
Solution Approach 1:
The patent changes the frequency parameter of the AC component in the composite test signal to an optimized value that maximizes phase difference detection accuracy for inductance measurement. By selecting a specific frequency that provides optimal measurement conditions, the system achieves high precision without requiring time-consuming frequency calibration procedures, as the optimal frequency is determined and applied directly.
4Measurement precision
If voltage is sharply changed to measure inductance response time, then inductance can be calculated, but level judgment and time measurement become erroneous
Solution Approach 1:
Instead of using a sharp voltage change, the patent employs a periodic AC component in the composite test signal for inductance measurement. The periodic nature of the AC signal provides regular, predictable cycles that make level judgment and time measurement more reliable, as the systematic oscillation allows for precise zero-crossing detection and phase angle measurement without the uncertainties associated with abrupt voltage transitions.
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
This approach enables accurate and rapid calculation of the motor constant, reducing measurement time and errors, and is less influenced by noise, with high accuracy in determining the motor constant and inductance values.
Implementation Method 1
a voltage obtained by compositing a DC component and an AC component is applied to the motor
Data Source
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AI summary
A method for calculating a motor constant of a permanent magnet type synchronous motor according to the present invention includes: a voltage applying step of applying a voltage obtained by compositing a DC component and an AC component to a permanent magnet type synchronous motor while varying a frequency of the AC component; a current detecting step of detecting a motor current flowing according to the applied voltage; a phase difference calculating step of calculating a difference in phase between the AC component of the applied voltage and an AC component of the motor current; and a motor constant calculating step of calculating a motor constant of the permanent magnet type synchronous motor. In addition, in the motor constant calculating step, the motor constant is calculated based on the applied voltage and the motor current when the difference in phase becomes nearly 45 degrees.