Solid State Relay Phase Sequence Control
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Solution Overview
Problem
Existing three-phase solid state relays for AC motors face issues with phase sequence changes and phase lack, leading to motor reversal, damage to mechanical parts, and potential burnout, due to the complexity and cost of external equipment required for phase detection and control.
Innovation Solution
A solid state relay with integrated phase sequence detection, phase lack detection, automatic phase correction, and phase lack protection logic, utilizing discrete components to provide centralized, safe, and low-cost control of three-phase AC motor direction, eliminating the need for external MCU/DSP controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external equipment (phase sequence protector and controller MCU) is used to detect and control phase sequence, then phase sequence control capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent integrates phase sequence detection, phase lack detection, and control logic functions directly into the solid state relay module. The detection modules and logic unit are merged with the power components (thyristors) to form a unified integrated circuit, eliminating the need for separate external MCU and phase sequence protectors. This consolidation maintains reliable phase sequence control while significantly reducing system complexity and component count.
Solution Approach 2:
The solid state relay module is designed to perform multiple functions simultaneously: it acts as a power switch, phase sequence detector, phase lack detector, and control logic unit. This multi-functional design allows a single device to replace what would traditionally require multiple separate components, thereby improving phase sequence control capability without increasing overall system complexity.
2Reliability
If external equipment is used for phase detection and control, then phase sequence control capability is improved, but manufacturing cost increases
Solution Approach 1:
By merging the detection modules and control logic into the solid state relay module itself, the patent eliminates the need for separate external components such as phase sequence protectors and MCU units. This integration reduces the total bill of materials and assembly costs, making the manufacturing process more economical while maintaining reliable phase sequence control capability.
3Adaptability or versatility
If two groups of power components are switched for motor direction control, then motor running direction control capability is improved, but risk of internal interphase short circuit increases
Solution Approach 1:
The patent incorporates detection modules that continuously monitor the phase sequence and power supply status. These detection modules provide feedback to the control logic unit, which then adjusts the switching of power components accordingly. This feedback mechanism ensures that direction control is achieved while preventing conditions that could lead to internal interphase short circuits, thereby maintaining both versatility and reliability.
Solution Approach 2:
The detection modules detect phase sequence and power supply status before the switching action occurs. The control logic unit uses this advance information to prepare appropriate switching commands, ensuring that power components are switched only under safe conditions. This preliminary detection and preparation prevents internal interphase short circuits while enabling reliable motor direction control.
4Device complexity
If thyristor is used as power component with special turn-off characteristics, then power component simplicity is improved, but control precision deteriorates due to incomplete cut-off
Solution Approach 1:
The patent introduces detection modules and a control logic unit as intermediaries between the thyristor power components and the control signal. These intermediaries precisely monitor phase sequence and power supply status, then generate appropriately timed gate control signals for the thyristors. This intermediary control mechanism ensures complete and precise turn-off of thyristors, overcoming their inherent turn-off characteristics while maintaining the simplicity of using thyristor-based power components.
Data Source
AI summary
A solid state relay for controlling a three-phase AC motor running direction is provided, a driver module, power components module, phase sequence detection module, phase lack detection module, and automatic phase correction and phase lack protection logic module. The input of the phase sequence detection module is connected to the three-phase power supply, and the output is connected to the automatic phase correction and phase lack protection logic module, to provide phase sequence detection and a phase sequence signal to the automatic phase correction and phase lack protection logic module. The input of the phase lack detection module is connected to the three-phase power supply, and the output is connected to the automatic phase correction and phase lack protection logic module, to detect a lack of phase and provide the lacking phase signal to the automatic phase correction and phase lack protection logic module.