Contactor Switching via Phase-Angle Time Point Selection
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Solution Overview
Problem
Existing contactors for three-phase loads experience uneven wear of contacts due to synchronization with the main electric network, leading to differential arc energies and reduced service life as one contact fails faster than others.
Innovation Solution
A method involving a pre-arranged time point selection scheme distributes instant opening commands across main contacts, using intervals and offsets based on phase angles to evenly distribute burdens and prevent overheating, eliminating the need for current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contactor switches main contacts synchronized with the control voltage phase angle, then the switching operation is simple and reliable, but the contacts experience uneven erosion and different arc energies leading to reduced service life
Solution Approach 1:
The patent implements periodic switching operations where the contactor opens and closes contacts at predetermined time points within each period of the control voltage. By distributing multiple opening commands at different phase angles within one period and repeating this pattern, the switching operations are periodic. This ensures that different contacts experience switching at different phase angles over time, distributing the erosion and arc energy evenly across all contacts, thereby extending service life while maintaining reliable switching operation.
2Duration of action of stationary object
If multiple opening commands are distributed at different phase angles within one period, then the erosion and heat are evenly distributed on contacts, but the control circuit complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple time points within one period of the control voltage before actual switching operations begin. These predetermined time points correspond to different phase angles and are stored in the control circuit. When switching is needed, the controller simply selects one of these pre-calculated time points to issue the opening command, avoiding the need for complex real-time calculations. This preliminary preparation simplifies the control logic while achieving even distribution of erosion and heat across contacts.
Solution Approach 2:
The patent introduces dynamic selection of switching time points based on the operational state and requirements. Rather than using a fixed switching schedule, the control circuit dynamically selects appropriate time points from the predetermined set within each period. This dynamic approach allows the system to adapt to different operating conditions while maintaining the benefit of distributed phase angles, achieving a balance between extended contact life and manageable control complexity.
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 extends the service life of the contactor by ensuring even erosion and heat distribution across contacts, reducing the risk of overheating and prolonging operational performance.
Implementation Method 1
an actuating unit having a coil, main contacts operated by the coil
Implementation Method 2
The electrical load or burden on each of the contacts will therefore differ substantially, which results in substantially different arc energies
Data Source
Figure 1
Figure 2~3
Figure 4a~4b
AI summary
The present invention relates to a low voltage contactor (1) for connecting and disconnecting a three-phase load (2) to an electric power including a coil (16), main contacts (12) operated by the coil (10) and an electronic control circuit (20) for controlling voltage supplied to the coil. The electronic control circuit includes a pre-arranged time point selection scheme (22) and is further adapted to select a time point from the pre-arranged time point selection scheme (22) as a time delay, and initiate an instant opening command based on the selected time point.