Variable Speed Drive Stator Heating Transistor Load Sharing
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Solution Overview
Problem
The existing motor drive systems using power transistors for preheating motor stators subject a single IGBT to high current stress, leading to significant degradation over the lifespan of the system, reducing the overall lifespan and reliability of drive components.
Innovation Solution
An electric drive system that includes a direct current power source, multiple power supply and return transistors, and a control unit that switches transistors in a round-robin fashion, selecting the least used transistors for subsequent heating demand events, based on time or ampere-hours, to distribute the heating current more evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single IGBT is used for stator heating current, then the heating function is achieved, but the IGBT degrades significantly over time
Solution Approach 1:
The patent divides the single IGBT function into multiple IGBTs (at least two) that share the heating current load. Each IGBT handles a portion of the total current, segmenting the stress distribution and preventing any single device from experiencing excessive degradation.
Solution Approach 2:
The patent combines multiple IGBTs to work together for the heating function. By merging multiple devices in parallel or alternating configurations, the system achieves both the heating requirement and reduced individual stress through load sharing.
2Temperature
If high current is applied to heat the stator winding, then the preheating effectiveness is improved, but the IGBT experiences significant degradation
Solution Approach 1:
The high current required for effective stator heating is segmented across multiple IGBTs. Instead of one IGBT handling the full high current, multiple devices share the load, maintaining heating effectiveness while reducing individual device stress and improving reliability.
3Duration of action of moving object
If continuous heating is performed, then the preheating function is maintained, but the IGBT lifespan is reduced
Solution Approach 1:
The patent implements periodic switching of IGBTs during continuous heating operations. By alternating between multiple IGBTs in a cyclic manner, the system maintains continuous heating functionality while allowing individual IGBTs to rest and cool, thereby extending their operational lifespan.
Solution Approach 2:
The continuous heating duration is segmented across multiple IGBTs through load sharing. Each IGBT operates for a portion of the total heating time, dividing the cumulative stress and extending the operational life of individual components while maintaining continuous heating capability.
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
This approach extends the lifespan of power transistors by reducing the cumulative stress on individual transistors, thereby enhancing the reliability and longevity of the drive system components.
Implementation Method 1
A preheat mode of an idle compressor generates heat within the windings of the idle compressor motor
Data Source
AI summary
An apparatus and method for extending component life in a motor drive having a stator heating mode is disclosed. The current supplied to stator windings is cycled through a set of primary stator power transistors to increase the overall lifespan of the drive, thus preventing premature failure of the stator power transistors by splitting the workload between them, rather than having a single transistor supply the bulk of the stator heating current.