Encoderless Synchronous Motor Parameter Identification
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Solution Overview
Problem
Existing methods for determining electrical equivalent circuit diagram parameters of three-phase synchronous motors require electrical or mechanical loading, which can lead to overloading risks and are not suitable for characterizing electrical behavior across a large frequency range without mechanical sensors.
Innovation Solution
A method that feeds a test signal into the d-flux axis of a stationary rotor, allowing for the measurement of equivalent circuit diagram parameters without mechanical loading, using signal-theoretical methods to transform time domain data into the frequency domain and extract parameters using a pseudo-noise binary signal and Fourier transformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct current and short-circuit tests are performed to determine equivalent circuit parameters, then the electrical behavior can be characterized, but the motor requires mechanical loading and locking which creates overloading risks
Solution Approach 1:
The patent replaces mechanical loading and locking systems with an electrical test signal injection method. Instead of mechanically loading the motor and locking the rotor for traditional DC and short-circuit tests, the invention uses electrical signals injected into the motor windings to excite the system and measure the equivalent circuit parameters electrically, thereby eliminating mechanical overloading risks
Solution Approach 2:
The patent changes the test conditions from mechanical domain parameters (load, speed, position) to electrical domain parameters (test signal frequency, voltage, current). By sweeping through a range of frequencies and measuring the electrical response, the equivalent circuit parameters are determined without requiring mechanical loading or rotor locking
2Measurement precision
If traditional time domain methods are used for parameter determination, then the motor must be driven in a test environment, but this limits the frequency range characterization
Solution Approach 1:
The patent employs periodic test signals with varying frequencies swept across a wide range to excite the motor. By using periodic excitation signals at different frequencies and measuring the steady-state response, the method characterizes the equivalent circuit parameters across the entire frequency range, not just at operating speed
Solution Approach 2:
The patent transitions from static time-domain measurement (single operating point) to dynamic frequency-domain measurement. The system dynamically sweeps through frequencies and captures the frequency response, enabling characterization of the motor's electrical behavior across the full frequency spectrum rather than at a single operating condition
3Loss of information
If measurement results from mechanical sensors are used to derive operating behavior correlations, then speed-dependent behavior can be analyzed, but this requires additional mechanical sensors like rotary encoders
Solution Approach 1:
The patent extracts the necessary information for operating behavior correlation directly from electrical measurements (voltages and currents) without extracting or requiring mechanical sensor data. The frequency response measurements provide sufficient information to characterize the motor's electrical behavior across different operating conditions without mechanical sensors
Solution Approach 2:
The patent substitutes mechanical sensing systems with electrical measurement systems. Instead of using rotary encoders or other mechanical sensors to track rotor position and speed for deriving operating correlations, the invention uses electrical test signal injection and measurement to obtain all necessary information from the electrical domain alone
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
Enables the determination of equivalent circuit diagram parameters without mechanical loading, providing accurate characterization of electrical behavior across a wide frequency range and enabling optimized motor control and monitoring without the need for rotary encoders.
Implementation Method 1
a test signal voltage U 1d is fed in to the d-flux axis direction of the rotor and a measurement signal current I 1d resulting therefrom is measured
Implementation Method 2
signal-theoretical methods to transform time domain data into the frequency domain and extract parameters using a pseudo-noise binary signal and Fourier transformations
Data Source
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AI summary
The invention relates to a method for the encoderless identification of equivalent circuit parameters (15) of a three-phase synchronous motor (09). The method comprises at least the following steps: - finding the stationary position of the rotor (11) such that the d-flux axis of the rotor is aligned with the α-axis of the stator (13); - injecting a test signal voltage U1d in the d-flux axis direction of the synchronous motor (09), whereby the q-transverse axis direction remains unenergized; - measuring the d-flux axis current /1d of the d-flux axis direction of the synchronous motor (09); - identifying equivalent circuit parameters of the synchronous motor (09) based on the test signal voltage U1d and the d-flux axis current; wherein the test signal is injected into the synchronous motor (09) such that the rotor (09) remains free of torque.In related aspects, the invention relates to an identification device (39) for determining equivalent circuit parameters (15) of a synchronous motor (09) and a motor control device (35) comprising this device, wherein the identified equivalent circuit parameters (15) can be used to determine, optimize, and monitor motor control. Finally, the invention proposes using the identification method for controlling electric drives.