Freewheeling diode current under open-phase fault in field-weakening region of multiple three-phase drives

Stare, Živa (author), Lavrič, Henrik (author), Nemec, Mitja (author), Drobnič, Klemen (author)

Multiple three-phase machine drives are inherently fault-tolerant due to their multiphase structure; however, they remain susceptible to inverter-related faults. A common fault is the loss of gate signals in one inverter leg, resulting in an open-phase condition. Under such conditions, a reverse conduction path is established through the freewheeling diodes of the faulted leg, leading to uncontrolled freewheeling diode current generation. The resulting freewheeling diode current becomes particularly critical in the field-weakening region, when the back-EMF may exceed the DC-link voltage and a large reverse current can occur. This paper derives an analytical expression for real-time prediction of the freewheeling diode current in a triple three-phase surface-mounted permanent magnet synchronous machine drive. The method is applicable in both the constant-torque and field-weakening regions. The analytical prediction is validated through comparison with both experimentally measured and numerically simulated freewheeling diode current waveforms over a wide range of operating points, including no-load and loaded conditions. The results show that the proposed model accurately reproduces the envelope and conduction boundaries, while maintaining good agreement with simulations and measurements. The predicted current can be utilized in post-fault control, fault detection, and sensorless position estimation.

• Language: English
• Keywords: multiple three-phase machine, open-phase fault, field-weakening, freewheeling diode current, uncontrolled generation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FE - Faculty of Electrical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 28 str.
• Numbering: Vol. 16, issue 12, art. 5994
• PID: 20.500.12556/RUL-183619
• UDC: 621.313/.314
• ISSN on article: 2076-3417
• DOI: 10.3390/app16125994
• COBISS.SI-ID: 281786371
• Publication date in RUL: 16.06.2026

Record is a part of a journal

• Title: Applied sciences
• Shortened title: Appl. sci.
• Publisher: MDPI
• ISSN: 2076-3417
• COBISS.SI-ID: 522979353

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: večfazni stroj, napaka v močnostnem pretvorniku, napaka odprtih stikal, slabljenje polja, tok prostoročne diode

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P2-0258
• Name: Pretvorniki električne energije in regulirani pogoni