Stepping Motor Driver Coil Disconnection Detection
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Solution Overview
Problem
Existing motor driving devices face challenges in accurately detecting coil disconnection in Permanent Magnet (PM) motors, leading to false detection of avalanche currents, which can result in thermal destruction of switching elements due to delayed detection timing.
Innovation Solution
A motor driving device with a switching element connected to a stepping motor coil and a rectifier element for detecting negative currents, ensuring the switching element remains off if a negative current greater than a predetermined value is not detected after being on, preventing thermal destruction by accurately distinguishing between normal and disconnected coil states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching element is turned off after being on to transfer energy between coils, then energy transfer efficiency is improved, but the risk of avalanche state and thermal destruction increases when coil disconnection occurs
Solution Approach 1:
The patent applies preliminary action by detecting coil connection status before the switching element is turned off. The detection unit checks whether the coil is properly connected prior to enabling energy transfer, and the control unit prevents the switching element from turning off if disconnection is detected. This advance detection and prevention mechanism resolves the contradiction by eliminating the risk of avalanche state while maintaining efficient energy transfer when coils are properly connected.
2Measurement precision
If avalanche current detection is delayed to accommodate PM motor characteristics, then false detection is reduced, but thermal destruction risk increases due to delayed protection
Solution Approach 1:
The patent performs coil connection status detection before the switching element turns off, rather than waiting for avalanche current to occur. By checking the coil status in advance and preventing the switching element from turning off when disconnection is detected, the system eliminates both false detection and delayed protection. This preliminary detection approach resolves the contradiction by providing accurate detection without sacrificing protection timing.
3Productivity
If the switching element operates at high frequency to improve productivity, then manufacturing efficiency is improved, but the temperature increase and thermal destruction risk worsen
Solution Approach 1:
The patent implements preliminary detection of coil connection status before each switching operation. By detecting potential disconnection issues in advance and preventing switching element operation when problems are detected, the system avoids avalanche states that would cause excessive temperature increases. This allows high-frequency operation for improved productivity while maintaining acceptable temperature levels through preventive protection.
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
Prevents false detection of coil disconnection and thermal destruction by accurately identifying negative currents, ensuring the switching elements are kept off when necessary, thus maintaining device integrity across various motor specifications.
Implementation Method 1
a rectifier element having one end connected to the other end of the second coil, and having the other end connected to the ground side, the rectifier element configured to be energized in a direction from the ground side toward the second coil
Implementation Method 2
the other end of the first coil and one end of the second coil electromagnetically coupled and connected to a power source side
Data Source
AI summary
A motor-driving device comprising: a switching element to control a current passed through a first coil of a stepping motor including the first and a second coils electromagnetically coupled; a rectifier element to be energized in a ground-side-to-second-coil direction; a coil-current-detection unit to detect a current passed through the first coil; a regeneration-current-detection unit to detect a current passed through the rectifier element; a control unit to turn off the switching element when the current passed through the first coil reaches a predetermined-set current based on a detection result of the coil-current-detection unit; and a negative-current-detection unit to detect whether a negative current greater in absolute value than a predetermined-set value is passed through the rectifier element based on a detection result of the regeneration-current-detection unit, the control unit keeping the switching element off when the negative current is not passed, based on a detection result of the negative-current-detection unit.