Active Grounding Resonant Circuit for High Frequency Shaft Voltage
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Solution Overview
Problem
Existing solutions fail to effectively prevent harmful shaft voltages and their frequency components from causing bearing currents in electrical machines, leading to damage despite conventional grounding methods.
Innovation Solution
A method that involves identifying undesired frequency components of voltages by measuring or simulating signals, and providing resonant circuits at specific grounding locations to create a low impedance path for these frequencies, using capacitors and inductors in parallel or series to resonate at the identified frequencies above 500 Hz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional grounding methods are used, then low frequency shaft voltages are mitigated, but high frequency shaft voltages above 500 Hz are not effectively prevented
Solution Approach 1:
The grounding system uses a variable impedance network that dynamically adjusts its characteristics based on frequency. The network includes resistive, capacitive, and inductive elements that can be switched or adjusted to provide optimal grounding impedance at different frequency ranges, making the system adaptive to both low frequency and high frequency shaft voltages
Solution Approach 2:
The grounding system changes its electrical parameters (resistance, capacitance, inductance) depending on the operating conditions and frequency content of shaft voltages. By adjusting these parameters, the system can effectively ground both low frequency voltages (using primarily resistive paths) and high frequency voltages (using capacitive and inductive paths), thus resolving the contradiction between reliability and adaptability across frequency ranges
2Reliability
If bearing isolation is used, then high frequency shaft voltages are partially mitigated, but the complexity of the grounding system increases
Solution Approach 1:
The invention merges the bearing isolation function with the shaft grounding function into a single integrated grounding system. Instead of using separate bearing isolation devices and shaft grounding devices, the system combines these functions into one unified grounding network that provides both high frequency mitigation and shaft voltage protection, thereby reducing overall system complexity while maintaining effectiveness
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 effectively reduces the amplitude of harmful frequency components, preventing bearing currents and extending the lifespan of electrical machine components by providing an efficient grounding path even at high frequencies where conventional methods fail.
Implementation Method 1
providing the electrical machine with a first grounding at a grounding location, the first grounding comprising a resonant circuit resonating at the first undesired frequency
Implementation Method 2
there are many potential current paths via capacitive couplings from the shaft and from the stator core laminations to ground
Implementation Method 3
the capacitive grounding 8, 9, 27 may additionally comprise an inductance 32 in series with a capacitance 9
Data Source
AI summary
A method for preventing a frequency component of a voltage from occurring in an electrical machine including the steps of: obtaining, either by measuring a voltage signal or a current signal from the electrical machine in time domain and transforming the measured signal into frequency domain, by simulating or deducing a first frequency component present in the electrical machine in absence of a grounding, the first frequency component representing a first undesired frequency higher than a limit frequency of 500 Hz; and providing the electrical machine with a first grounding at a grounding location, the first grounding including a resonant circuit resonating at the first undesired frequency. In order to get rid of harmful shaft voltages in the form of sharp voltage peaks at high frequencies, it is first necessary to determine at which undesired frequency or frequencies these voltage peaks occur. Only thereafter can a low impedance grounding be provided that works satisfactorily at the undesired frequency or frequencies.