Synchronous Motor Restart Control for Residual Load and Peak Current
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Solution Overview
Problem
Synchronous motors used in compressors face unpredictable load conditions during restart, 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 mode duration based on these values when restarting, allowing for optimized current flow and reduced peak currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If maximum start current is applied to ensure successful start under maximum load conditions, then start reliability is improved, but circuit life deteriorates due to repeated large current flow affecting IGBTs
Solution Approach 1:
The patent applies dynamics by making the start current adaptive rather than fixed. The control device dynamically adjusts the target current value based on real-time operating conditions (stored current and rotation speed values), transforming the static maximum current approach into a dynamic, condition-based current control strategy that optimizes both start reliability and circuit life.
Solution Approach 2:
The patent changes the parameter of start current from a constant maximum value to a variable value determined by stored operating parameters. By modifying the current parameter based on previously stored current and rotation speed values, the system achieves reliable starts under varying load conditions while reducing excessive current flow that would otherwise damage the circuit.
2Reliability
If maximum start current is used to overcome unknown load conditions after compressor stop, then start performance is improved, but energy consumption increases due to unnecessary large current flow
Solution Approach 1:
The patent applies partial action by providing just enough current to overcome the actual load conditions rather than always applying maximum current. By using stored current and rotation speed values to determine an appropriate target current value, the system delivers partial current when load conditions permit, reducing energy consumption while maintaining sufficient start performance.
Data Source
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.