Phase-to-Phase Insulation Inspection Using Filtered Impulse Voltage
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Solution Overview
Problem
Inverter-driven rotary electric machines face challenges in inspecting phase-to-phase insulation without being influenced by partial discharges that may occur between winding turns, due to increased voltage rise times and surge impedance mismatches, which can lead to incorrect insulation reliability assessments.
Innovation Solution
The solution involves setting the surge propagation time period and partial discharge inception voltage for the rotary electric machine such that an impulse voltage with specific rise time and oscillation characteristics does not cause partial discharge between winding turns, allowing for precise inspection of phase-to-phase insulation using an impulse voltage with controlled rise time, oscillation frequency, and damped oscillation, ensuring that partial discharge does not occur between phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an impulse voltage with fast rise time is applied to inspect phase-to-phase insulation, then inspection sensitivity is improved, but partial discharge between winding turns occurs causing incorrect inspection results
Solution Approach 1:
The patent changes the time domain parameters of the inspection voltage by applying a band-pass filtered impulse voltage that attenuates frequency components above a predetermined threshold. This filtering modifies the voltage waveform to have a controlled rise time that prevents partial discharge between winding turns while maintaining sufficient inspection sensitivity for phase-to-phase insulation defects.
Solution Approach 2:
The patent introduces a band-pass filter as an intermediary device between the impulse voltage generator and the rotary electric machine. This filter mediates the voltage waveform by removing high-frequency components that cause partial discharge between winding turns, while preserving the essential inspection characteristics for phase-to-phase insulation.
2Reliability
If insulation thickness is increased to prevent partial discharge, then insulation reliability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent performs preliminary action by applying a band-pass filtered impulse voltage during the inspection stage to detect potential insulation issues before they lead to failure. This allows the use of standard insulation designs without requiring increased insulation thickness, as the inspection method proactively identifies weaknesses early.
Solution Approach 2:
The patent replaces the mechanical approach of increasing insulation thickness with an electrical approach of using filtered impulse voltage for inspection. Instead of physically modifying the insulation structure to prevent partial discharge, the solution uses signal processing to eliminate the harmful high-frequency components that cause partial discharge during inspection.
3Productivity
If inverter switching speed is increased to improve productivity, then energy saving efficiency is improved, but voltage surge and partial discharge risk increase
Solution Approach 1:
The patent uses periodic band-pass filtered impulse voltages for inspection, where each impulse is carefully shaped to have controlled rise time. This periodic inspection approach allows the inverter to operate at high switching speeds for productivity, while the inspection method periodically checks for insulation degradation caused by the high-frequency switching surges.
Solution Approach 2:
The patent converts the harmful high-frequency voltage surges generated by fast inverter switching into a beneficial inspection opportunity. By using band-pass filtered impulse voltages that mimic the spectral characteristics of inverter surges but with controlled amplitude and rise time, the method detects insulation weaknesses caused by inverter operation without causing damaging partial discharge.
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 the provision of an inverter-driven rotary electric machine with appropriate insulation performance, allowing for the occurrence of partial discharge between winding turns while ensuring the phase-to-phase insulation performance is accurately assessed, thereby enhancing insulation reliability and preventing incorrect inspection results.
Implementation Method 1
partial discharge inception voltage PDIV between winding turns are set such that partial discharge does not occur even if an impulse voltage having a voltage rise time period tr and a voltage peak Vmax which satisfy an expression (A1) given below is applied
Implementation Method 2
a surge propagation time period τcoil of one coil and a partial discharge inception voltage PDIV between winding turns of a rotary electric machine winding are set
Data Source
AI summary
A phase-to-phase insulation partial discharge inspection apparatus includes: an impulse power supply (1) configured to apply an impulse voltage having a voltage rise time period tr which satisfies an expression “tr>(τcoil·Vmax)/(PDIV)” to a rotary electric machine (2); a measurement section (12) configured to measure partial discharge which occurs when the impulse voltage is applied to the rotary electric machine (2); and a decision section (15) configured to determine that, when partial discharge is not measured by the measurement section (12), a phase-to-phase insulation performance is acceptable. In the expression, τcoil is a surge propagation time period of one coil of a rotary electric machine winding, PDIV a partial discharge inception voltage between winding turns, and Vmax a peak of a partial discharge testing voltage for the phase-to-phase insulation.