Electric Machine Insulation Impedance Testing for Service-Life Prediction
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Solution Overview
Problem
Existing insulation diagnostic methods for electric machines can damage the machine and are unreliable in predicting the remaining service life due to the need for high voltages and partial discharges, which can further degrade the insulation material.
Innovation Solution
An insulation measuring device applies multiple AC voltages with varying amplitudes and frequencies to determine impedance between phase and earth connections, creating an impedance curve to assess insulation conductance and capacitance, allowing early detection of insulation failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If partial discharge measuring is used to detect insulation degradation, then insulation failure can be detected, but the high voltage required causes further damage to the insulation material and reduces remaining service life
Solution Approach 1:
The patent changes the measurement parameters from high voltage partial discharge to low voltage impedance measurement across multiple frequencies. By measuring impedance at different frequencies (including power frequency and higher frequencies) and analyzing the results through equivalent circuit models, the system detects insulation degradation without applying damaging high voltages. The impedance measurements at multiple frequencies provide information about insulation conductance and capacitance changes that indicate degradation.
2Measurement precision
If high voltage is applied to induce partial discharges for insulation diagnosis, then insulation condition can be assessed, but the service life of the electric machine is reduced due to cumulative damage
Solution Approach 1:
The patent replaces the mechanical/electrical stress method (high voltage partial discharge) with an electrical measurement method (impedance spectroscopy). By using impedance measurements at multiple frequencies and analyzing the data through equivalent circuit models, the system achieves precise insulation condition assessment without the mechanical damage caused by high voltage stress. The method substitutes direct high voltage stress with indirect electrical characterization.
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 accurate prediction of insulation failure before it occurs, enabling proactive maintenance or replacement of the electric machine, reducing the risk of damage.
Implementation Method 1
an impedance between the phase connection and the earth connection is calculated in a subsequent calculation step using the insulation measuring device
Data Source
AI summary
The invention relates to a method for determining a remaining service life of an electric machine using an insulation measuring device and an electric machine, the insulation measuring device having at least one electric voltage source and the at least one electric voltage source of the insulation measuring device being electrically conductively connected to a phase connection and an earth connection of the electric machine. An object, which is to be able to determine the remaining service life of the electric machine as well as possible, is achieved according to the invention, an electric AC voltage having an amplitude and a frequency being applied in a measuring step between the phase connection and the earth connection using the voltage source, an electric alternating current brought about by the applied electric AC voltage being detected in the phase connection in a subsequent detection step using the insulation measuring device, an impedance between the phase connection and the earth connection being calculated in a subsequent calculation step using the insulation measuring device, and the measuring step, the detection step and the calculation step being repeated with at least one further electric AC voltage having a different amplitude and/or a different frequency, so that a remaining service life of the electric machine can be determined with the aid of the calculated impedances.