Transformer Inrush Current Reduction via Pre-magnetization and Phase Control
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Solution Overview
Problem
Inrush currents caused by transformers switching on in electrical networks can lead to significant load on the supply network, particularly when transformers are connected at unfavorable phase positions relative to residual magnetism, resulting in high magnetizing currents that negatively impact voltage quality, especially in wind farms with low short-circuit power.
Innovation Solution
A method involving pre-magnetization of the transformer to a known magnetic state and recording the phase angle profile of the mains voltage to determine the optimal switch-on time, allowing the transformer to be connected when the phase angle is favorable, thereby minimizing inrush currents without needing to measure remanence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the transformer is connected to the electrical network at an arbitrary point in time, then the connection process is simple, but high inrush currents occur due to unfavorable phase position relative to remanence
Solution Approach 1:
The patent applies preliminary action by pre-magnetizing the transformer core in a controlled manner before connection to the electrical network. A DC voltage is applied to the primary winding to establish a predetermined magnetic state with minimal remanence, and the connection is timed to occur at a specific phase angle of the mains voltage (typically when the voltage crosses zero). This preliminary preparation eliminates the need for complex remanence measurements while minimizing inrush currents.
2Object-generated harmful factors
If the transformer is pre-magnetized and connected at an optimized phase angle, then inrush currents are reduced, but the connection process becomes more complex
Solution Approach 1:
The patent changes key parameters including applying DC voltage to establish a predetermined magnetic state, timing the connection at a specific phase angle of the mains voltage (typically 0 degrees), and controlling the magnetization current magnitude. These parameter changes are implemented through a control unit that manages the switching device and voltage application timing, achieving inrush current reduction with manageable complexity.
3Measurement precision
If remanence measurement is performed before connection, then the optimal switch-on time can be determined, but the system requires complex monitoring and individual adaptation
Solution Approach 1:
The patent extracts and eliminates the need for complex remanence measurement systems by using a different approach: applying a known DC voltage to establish a predetermined magnetic state before connection. This removes the disturbing element (complex monitoring) while achieving the same goal of minimizing inrush current through controlled magnetization and phase-angle-based switching.
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 reduces inrush currents by coordinating the transformer's connection with the electrical network's phase angle, simplifying the process and avoiding complex remanence measurements, thus minimizing the impact on the supply network.
Implementation Method 1
These inrush currents arise when the transformer is switched on by magnetization processes or magnetic saturation processes in the iron core.
Implementation Method 2
When electrically connecting the transformer to a live network, unwanted and high inrush currents can occur. These inrush currents of the transformer, also generally referred to as inrush currents, can represent a strong and unwanted load on the electrical supply network.
Implementation Method 3
The residual magnetism that is present in a transformer is also understood as remanence. Depending on when the transformer was switched off, a different residual magnetism remains in the core of the transformer, which is usually also unknown.
Data Source
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Figure 3~4A
AI summary
The invention relates to a method for electrically connecting a transformer (316) to an electrical network (320) having a network voltage via a power switching device (322), wherein the transformer has a primary side (324) and a secondary side (326) on the network side, comprising the steps of premagnetizing the transformer before the electrical connection is carried out in order to achieve a predetermined magnetized state of the transformer, capturing a phase angle profile of the network voltage, connecting the transformer to the electrical network by closing the power switching device, wherein the closing is carried out on the basis of the predetermined magnetized state of the transformer and on the basis of the captured phase angle profile.