Solid-State Motor Starter Current Detection for Phase Reversal
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Solution Overview
Problem
Current methods for detecting the forward and reverse connection of three-phase motors, such as using microswitches or frequency converters, increase design complexity and cost, necessitating a simpler and cost-effective solution.
Innovation Solution
A method utilizing a solid-state motor starter with a solid-state switch module and a forward and reverse switch module to detect the connection state by monitoring output current through a current detection unit, determining the connection state based on current flow patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microswitch or auxiliary contact detection is used to determine contactor state, then forward and reverse connection detection is achieved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the detection function from external components (microswitches, auxiliary contacts) and integrates it directly into the solid-state motor starter's existing current detection unit. The control unit analyzes current flow patterns during a brief conduction period to determine connection state, eliminating the need for separate detection mechanisms.
Solution Approach 2:
The solid-state motor starter's current detection unit, originally designed for motor protection, is made multi-functional by enabling it to also detect forward and reverse connection states. The control unit analyzes the same current signals for multiple purposes: protection and connection detection, reducing overall system complexity.
2Reliability
If microswitch or auxiliary contact detection is used to determine contactor state, then forward and reverse connection detection is achieved, but cost increases
Solution Approach 1:
The patent makes the existing current detection unit multi-functional, using it for both motor protection and forward/reverse connection detection. This eliminates the need for additional detection components, reducing bill of materials cost and simplifying manufacturing.
Solution Approach 2:
The solid-state motor starter performs self-detection of its own output connection state by analyzing its own current output signals. The control unit uses the existing current detection capability to determine whether the motor is connected in forward or reverse configuration, without requiring external detection devices.
3Adaptability or versatility
If frequency converter is used to achieve forward and reverse rotation control, then motor rotation control is achieved, but device complexity increases
Solution Approach 1:
The patent extracts the connection detection function from complex frequency converters or contactor-based systems and implements it within the solid-state motor starter using existing current detection capabilities. This simplifies the overall control system by eliminating the need for frequency converters when only forward/reverse detection is needed.
Data Source
AI summary
A method of detecting forward and reverse connection of a three-phase motor is disclosed, including: turning on a first solid-state switch pair and a second solid-state switch pair into conduction for a predetermined period of time so that current can flow between a power supply and the three-phase motor; detecting output current of a solid-state motor starter; and determining the forward and reverse connection state of the three-phase motor based on the output current of the solid-state motor starter, in a case that currents exist at a first output terminal and a second output terminal, it is determined that the three-phase motor is in the forward connection state, and in a case that currents exist at the first output terminal and a third output terminal, it is determined that the three-phase motor is in the reverse connection state. Furthermore, a solid-state motor starter is disclosed.