變頻驅動器短路故障之馬達響應與保護

Abstract

本篇論文研究目的在於永磁同步馬達驅動器可能發生的故障，且將重點放在驅動端最危險的短路故障，當短路故障發生後，驅動器會產生比額定運轉更高的短路電流，不只破壞驅動電路系統，且極有可能損害馬達的磁鐵磁力。 兩種不同的驅動器短路故障將會被討論，分別為對稱型短路故障(Symmetric Short-Circuit Fault-SSC Fault)與非對稱型短路故障(Asymmetric Short-Circuit Fault-ASC Fault)，針對對稱型短路故障，本研究試圖推導出故障後的數學模型，並研究不同類型的馬達設計參數對短路故障的影響，進而抑制穩態和暫態故障電流峰值。此外，非對稱型短路故障則被結論是最危險的短路故障，其峰值電流和退磁風險都遠比對稱型短路故障來得高，本研究提出硬體切換保護策略，當非對稱型短路發生時，驅動器會切換成對稱型短路控制，確保馬達在故障後，降低短路峰值電流造成的風險。 本研究所有短路故障的理論，將會藉由電路模擬來佐證，並建立有限元素法馬達模型來評估短路電流產生之退磁風險。最後會針對兩顆不同電氣常數的馬達進行實驗驗證

This paper aims to investigate potential fault characteristics for Permanent Magnet Synchronous Motors (PMSM). The inverter switch short-circuit is the primary focus. When the inverter short-circuit fault occurs, considerable short-circuit currents are induced. They not only damage inverter devices, but also results in the demagnetization in PM motors. Two common inverter short-circuit faults are investigated. They are respectively Symmetric Short-Circuit (SSC) Fault and Asymmetric Short-Circuit (ASC) Fault. For SSC fault, an analytical model is developed for the faulty motor drive. The influence of fault reflected short-circuit currents on PM motors with different parameters are analyzed. It is shown that the short-circuit current can be suppressed by properly selecting the motor parameters. In addition for ASC fault, the fault reflected short-circuit currents are significantly higher than the currents under SSC fault. A hardware protection strategy based on the SSC operating mode is proposed to mitigate these dangerous short-circuit currents, avoiding the risks in PM motors once ASC fault occurs. All the analytical models will be verified by the inverter circuit simulation. In addition, Finite Element Analysis (FEA) is performed to investigate the demagnetization of PM motor under either SSC or ASC fault. Finally, two PM motors with different time constants are experimental evaluated to verity electromagnetic responses after fault.