Contactor Control Device for Even Contact Erosion
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Solution Overview
Problem
The uneven erosion of contacts in three-phase contactors due to synchronization with the main electric network results in shorter service life, as some contacts experience higher wear and tear than others.
Innovation Solution
A method for controlling the contactor that involves selecting a deterministic delay time from a set of values to distribute the switching points along the voltage waveform, ensuring even wear on all contacts by energizing and de-energizing the coil based on specific measurements and criteria, such as RMS values and zero crossings, to initiate switching commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the contactor switches at synchronized phase angles with the main electric network, then the switching operation is simple and deterministic, but the main contacts experience uneven erosion with one contact failing first, limiting service time
Solution Approach 1:
The patent applies dynamics by making the delay time variable rather than fixed. The control device selects different delay times from a predetermined set of N values for different switching operations, causing the switching phase angle to vary dynamically. This dynamic adjustment distributes erosion evenly across all three main contacts, preventing any single contact from failing first and thereby extending the overall service time of the contactor while maintaining simple deterministic switching control.
2Device complexity
If the contactor uses fixed switching timing, then the control logic is simple, but the arc energy and erosion on main contacts are substantially different, reducing overall component lifespan
Solution Approach 1:
The patent implements periodic action by cycling through a predetermined set of N delay time values across different switching operations. The control device periodically selects different delay times from this set, creating a repeating pattern of varied switching timings. This periodic variation in switching phase angles ensures that all three main contacts experience similar arc energies and erosion levels over time, extending their service life while keeping the control logic relatively simple through the use of a pre-defined delay time set.
3Reliability
If the contactor switches at varying phase angles, then even wear is achieved on all contacts, but the control mechanism becomes more complex with pre-arranged time point selection schemes
Solution Approach 1:
The patent applies parameter changes by modifying the delay time parameter selected from a predetermined set of N values. Instead of changing the fundamental switching control mechanism, the invention varies only the delay time parameter to achieve different switching phase angles. This selective parameter variation distributes erosion evenly across all contacts while minimizing control mechanism complexity, as the control device only needs to select from pre-defined delay time values rather than implementing complex real-time calculations.
4Reliability
If more silver is used in contacts, then the service life of the contactor increases, but the product cost increases
Solution Approach 1:
The patent replaces the mechanical/material solution (using more silver contact material) with an electrical control solution (varying switching phase angles through different delay times). By changing the switching timing to distribute erosion evenly, the invention reduces the need for excessive silver material to compensate for uneven wear. This substitution of control strategy for material quantity reduces both silver usage and product cost while maintaining or extending contactor service life.
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 evenly distributes arc erosion and heat across all contacts, increasing the service life of the contactor and reducing the need for silver usage, thereby prolonging its operational lifespan and reducing costs.
Implementation Method 1
The contactor further comprises an actuating unit comprising a coil for actuating the main contacts
Implementation Method 2
The electrical load or burden on each of the main contacts will therefore differ substantially, which results in substantially different arc energies
Data Source
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AI summary
A method (30) for switching a contactor (1) is provided. The method (30) is performed by a control device (20) controlling a control voltage supplied to a coil (10) of the contactor (1), wherein the coil (10) is energized and de-energized to control the switching of the contactor (1). The method (30) comprises determining (31) a reference point of time, t1, based on a delay time, ΔT, wherein a starting point of the delay time ΔT is set in relation to a start-up of the method (30), estimating (32) a period, Tp, of the control voltage, determining (33) a duration of a measuring interval, Tm, based on the estimated period Tp of the control voltage, setting (34) starting point of a first measuring interval Tm based on the reference point of time t1, and setting starting points of subsequent measuring intervals equal to end point of an immediately preceding measuring interval, obtaining (35) measurements on the control voltage for the duration of the measuring interval Tm, and switching (36) the contactor (1) based on measurements made during the measuring interval Tm. A control device (20), computer program (23) and computer program product (22) are also provided.