Leakage Current Reduction via Non-Inverting Amplifier Phase Control
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Solution Overview
Problem
Conventional leakage current reducing apparatuses are ineffective in suppressing noise due to phase errors and amplification issues, leading to unstable operation and inadequate noise reduction, particularly in power conversion systems connected to AC power supplies.
Innovation Solution
A leakage current reducing apparatus that includes a voltage detection section, a filter apparatus, a voltage amplifier, and a current supply section with injection capacitors, which detects and amplifies leakage current and supplies current of the same phase to the connection lines, effectively reducing leakage current by adjusting the gain and using the capacitors for high-pass filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the gain of the amplifier circuit is increased to reduce noise, then noise suppression is improved, but stable operation cannot be obtained due to phase inversion at the frequency that maximizes amplification
Solution Approach 1:
Instead of using a conventional amplifier that inverts phase at high frequencies, the patent uses a operational amplifier configured in a non-inverting amplifier circuit. This inversion of the amplification configuration eliminates the phase inversion problem at high frequencies, allowing the gain to be increased for better noise suppression while maintaining stable operation. The non-inverting configuration ensures that the output voltage has the same phase as the input voltage across the entire frequency range.
2Device complexity
If a conventional amplifier circuit is used to detect and cancel common mode voltage, then the circuit can be simplified, but phase errors directly appear on the cancelling voltage source resulting in ineffective noise suppression
Solution Approach 1:
The patent changes the configuration parameter of the amplifier from inverting to non-inverting mode. This parameter change ensures that the phase relationship between the detected common mode voltage and the cancelling voltage is maintained correctly. The non-inverting amplifier produces an output voltage with the same phase as the input, which is crucial for effective noise cancellation. This allows the use of a relatively simple operational amplifier circuit while achieving effective noise suppression.
3Object-affected harmful factors
If the amplification factor is maximized to reduce leakage current, then leakage current reduction is improved, but noise is amplified due to phase inversion characteristics of the amplifier circuit
Solution Approach 1:
The patent inverts the conventional amplifier configuration from inverting to non-inverting mode. This ensures that when the amplification factor is maximized to reduce leakage current, the phase relationship is preserved and noise is not amplified due to phase inversion. The non-inverting configuration allows high gain operation without the harmful phase inversion effect that would otherwise amplify noise.
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
The apparatus effectively reduces leakage current by supplying current of the same phase, stabilizing operation, and allowing for increased gain without amplifying noise, while protecting the voltage amplifier and reducing low-frequency current output.
Implementation Method 1
the current supply section has a plurality of injection capacitors whose terminals on one side are connected to the connection lines and whose terminals on the other side are commonly connected to a common connection point, and applies the output voltage to the common connection point
Data Source
AI summary
In a system supplying power from an AC power supply to a three-phase motor via a converter and an inverter, a leakage current reducing apparatus is connected to a connection line between the AC power supply and the converter. A common mode transformer detects, as common mode voltage, common mode current flowing from the AC power supply to the connection line. The common mode voltage is inputted to a voltage amplifier via a filter apparatus. Output voltage obtained by voltage amplification passes through a capacitor and then is applied as an AC component to a neutral point of capacitors connected in a Y-connection fashion, so as to have the same phase as that of the common mode voltage. Thus, current having the same phase as that of the common mode current is supplied via the capacitors to the converter through the connection line, thereby reducing the common mode current.