Multipole Electromechanical Switching Device for Three-Phase Motor Starters
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Solution Overview
Problem
Three-phase motor starters using contactors result in high peak surge currents and torque pulsations, causing stress on power distribution networks and motor loads, and existing alternatives like motor drives and electronic soft starters are larger, more expensive, and have shorter lives.
Innovation Solution
A two-step connection process using electromagnetic switches, such as Single Pole Switches (SPS) or Delayed Pole Contactor (DPC), where some motor windings experience current flow before others, reducing surge currents and torque pulsations by controlling the connection timing of three-phase power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simultaneous connection of all three phases is used, then simple device structure is maintained, but high peak surge currents and torque pulsations occur
Solution Approach 1:
The patent divides the three-phase connection into separate segments by using individual electromagnetic switches for each phase. This allows each phase to be connected independently at different times, eliminating the simultaneous connection that causes surge currents while maintaining structural simplicity through standardized switch modules.
Solution Approach 2:
The patent applies preliminary action by connecting phases in a predetermined sequence rather than simultaneously. The first phase is connected before the other phases, allowing the motor to begin accelerating gradually. This staged approach prevents the sudden torque pulsations and surge currents that occur with simultaneous connection while keeping the device structure simple.
2Device complexity
If simultaneous connection of all three phases is used, then simple device structure is maintained, but torque pulsations cause mechanical stress
Solution Approach 1:
The patent segments the phase connection process using individual electromagnetic switches for each phase. This enables controlled sequential connection that eliminates torque pulsations and mechanical stress while maintaining structural simplicity through the use of standardized switch components.
Solution Approach 2:
The patent implements preliminary action by pre-planning the phase connection sequence. The first phase is connected before the others, allowing the motor to start smoothly without torque pulsations that cause mechanical stress, while the simple device structure is preserved through standardized switch design.
3Reliability
If higher trip levels are set on circuit breakers, then nuisance trips are avoided, but breaker's ability to minimize damage during faults is reduced
Solution Approach 1:
The patent applies preliminary action by eliminating the need for high trip levels through sequential phase connection. By connecting phases in sequence rather than simultaneously, surge currents are prevented at the source, allowing circuit breakers to maintain lower, more appropriate trip levels that provide better fault protection while avoiding nuisance trips.
4Object-generated harmful factors
If two-step connection process is used, then surge currents are reduced, but device complexity increases
Solution Approach 1:
The patent segments the switching function into three independent electromagnetic switches, one for each phase. This segmentation enables the two-step connection process to reduce surge currents while keeping each individual switch simple and standardized, thereby limiting the increase in overall device 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
The two-step connection process significantly reduces or eliminates surge currents and torque pulsations, extending the life of motor starters and reducing mechanical stress on drive trains, while maintaining adequate protection and efficiency.
Implementation Method 1
At present, both embodiments use DC electromagnets controlled by electronic means
Data Source
AI summary
A method and apparatus using electromagnetic switching in a two-step connection process is provided to minimize surge currents and torque oscillations in three-phase motors during starts.