Synchronous Motor Restart Current Control Under Residual Load
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Solution Overview
Problem
Synchronous motors used in compressors face unpredictable load conditions during restarts, leading to excessive current flow in inverter-type motor drive circuits, which reduces circuit life and increases the risk of start failures.
Innovation Solution
A motor control device that stores current and rotation speed values at the time of stop and adjusts the target current and start duration based on these values during restarts, allowing for optimized start performance while minimizing excessive current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If forced commutation control is performed with maximum start current to ensure successful start under maximum pressure difference, then start reliability is improved, but circuit life deteriorates due to repeated large current flow
Solution Approach 1:
The patent changes the start current parameter from a fixed maximum value to a variable value that adapts to the actual load condition. By detecting the running current before stop and using it to determine the appropriate start current magnitude, the system adjusts the electrical parameter (current) to match actual needs, avoiding unnecessary maximum current application and thereby extending circuit life while maintaining reliable starts.
Solution Approach 2:
The patent implements feedback by detecting the running current of the synchronous motor before it stops and using this information to determine the appropriate start current for the subsequent start mode. This feedback mechanism allows the control system to make informed decisions about start current magnitude based on actual load conditions, preventing excessive current flow that would harm circuit components.
2Adaptability or versatility
If maximum start current is applied to handle unpredictable load conditions, then adaptability to different load conditions is improved, but energy consumption increases
Solution Approach 1:
The patent dynamically changes the start current parameter based on detected load conditions. Instead of always applying maximum current, the system adjusts the current magnitude to match the actual load requirements, thereby reducing energy consumption while maintaining the ability to adapt to various load conditions through intelligent parameter selection.
Solution Approach 2:
The patent applies partial action by providing only the necessary amount of start current required for the actual load condition rather than always applying excessive maximum current. This approach ensures adequate starting torque for the given load while avoiding unnecessary energy waste from over-provisioning the start current.
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AI summary
A motor control device capable of executing a start mode that takes into consideration both the start performance with respect to a residual load and the life of a drive circuit is provided. A motor control device for executing a start mode in which a rotor is rotated by forced commutation control: stores a current value at the time when a stop command to a synchronous motor is issued; and decides, when a start command to the synchronous motor is issued after the issuance of the stop command, a target current value based on the stored current value in the start mode in response to the start command.