Comparison of TSEP Performances Operating at Homogeneous and Inhomogeneous Temperature Distribution in Multichip IGBT Power Modules

Temperature Sensitive Electrical Parameters (TSEPs) are used to determine the chip temperature of a single-chip IGBT power module by measuring one electrical device parameter. Commonly, most TSEPs have a linear relationship between the chip temperature and the electrical parameter. Like any sensor, preferred attributes of TSEPs include good accuracy, linearity, and sensitivity. For multichip Insulated Gate Bipolar Transistors (mIGBTs) modules, these can only be achieved when all chips have the same temperature. Equal chip temperatures among different semiconductor chips can be achieved when placing mIGBTs in environmental chambers to produce a homogeneous temperature distribution (HTD). In real applications, however, mIGBTs are power cycled and are exposed to inhomogeneous temperature distribution (ITD) where temperature differences exist between chips. Consequently, measuring one electric parameter only cannot represent each chip temperature which impacts the TSEP sensitivity, linearity, and accuracy. This paper compares the performance of ten TSEPs applied to a mIGBT module operating at HTD and ITD conditions in order to determine which TSEPs are most suitable for mIGBTs in real applications

Optical FBG-T Based Fault Detection Technique for EV Induction Machines

Electric vehicles (EV) represent a key technology to achieve a low-carbon transportation objective, whist induction motors are one of the promising topologies. The reliability of these machines is crucial to minimize the downtime, cost and unwanted human lives. Although several techniques are utilized in the condition monitoring and fault detection of electrical machines, there is still no single technique that provides an all-round solution to fault detection in these machines and thus hybrid techniques are used widely. This paper presents a novel non-invasive optical fiber technique in condition monitoring of induction machines and in the process detecting inter-turn short circuit faults. Owing to optical fiber's immunity to magnetic flux, a composite FBG-T sensor formed by bonding a giant magnetostrictive transducer, Terfenol-D, onto a fiber Bragg grating is utilized to sense machines' stray flux as a signature to determine the internal winding condition of the machines. A tri-axial auto datalogging flux meter was used to obtain the stray magnetic flux and test results obtained via LabView were analyzed in MatLab. Experimental and numerical results agree with each other and how that the FBG-T sensor accurately and reliably detected the short-circuit faults. Bragg shifts observed under short-circuit faults were in 100s of picometre range under various operating frequencies compared to the mid-10s of picometre obtained under healthy machine condition. These provide much promise for future EVs

In Situ Diagnosis of Multi-site Wire Bonding Failures for Multichip IGBT Power Modules Based on Crosstalk Voltage

The online detection of aging bond wires is key to the health status awareness of smart power converters. In this paper, a new health precursor of the gate voltage undershoot VGE(pk) of the complementary switch in the half-bridge structure is proposed. It can be used to identify and distinguish multi-site bonding wire failures for both insulated gate bipolar transistors (IGBTs) and freewheeling diodes (FWDs) in multichip IGBT modules. A theoretical analysis is conducted to derive this novel precursor, which is then verified by experimental results. Then, a dedicated read-out circuit is designed for the data acquisition front end that can be integrated into gate drivers for in-situ monitoring. Finally, the effectiveness of this method is evaluated under changing operating conditions including the DC-bus voltage, the load current, and the junction temperature. The effects of their fluctuations are studied and quantified, with corresponding calibration relationships provided to improve precursor accuracy

Gate-emitter Pre-threshold Voltage as a Health Sensitive Parameter for IGBT Chip Failure Monitoring in High Voltage Multichip IGBT Power Modules

IEEE This paper proposes a novel health sensitive parameter, called the gate-emitter pre-threshold voltage VGE(pre-th), for detecting IGBT chip failures in multichip IGBT power modules. The proposed method has been applied in an IGBT gate driver and measures the VGE at a fixed time instant of the VGE transient before the threshold voltage occurs. To validate the proposed method, theoretical analysis and practical results for a 16-chip IGBT power module are presented in the paper. The results show a 500 mV average shift in the measured VGE(pre-th) for each IGBT chip failure

IGBT Junction Temperature Estimation Using a Dynamic TSEP Independent of Wire Bonding Faults

Despite that many temperature-sensitive electrical parameters (TSEPs) have been discovered for the online estimation of the junction temperature of IGBT devices, their wide adoption in the field is yet to come. This is because they are most susceptible to both the aging status and operating points of IGBTs, which can result in inaccurate results if not attended. In this study, a novel dynamic TSEP, the gate voltage undershoot VGE(np) of the complementary IGBT switch, is proposed. It is based on the crosstalk effect and measured during the turn-off switching transition of the controlled IGBT switch for its temperature estimation. Its monotonic temperature dependence has been identified with implications for the changing load current and bus voltage, which are experimentally verified using a 1200 V/450 A IGBT module. The theoretical analysis and experimental results also show that VGE(np) is independent of bond wire failures while providing comparatively high relative sensitivity. The MMC power equivalent experimental results are given to verify the feasibility of the proposed method in commercial engineering applications. Finally, the multivariate linear regression method is used to improve the ability to estimate the IGBT's temperature by accounting for the operating point

Evaluation of the turn-off transient controllability for high-power IGBT modules

The efficient and flexible conversion of electrical energy is increasingly accomplished by megawatt insulated gate bipolar transistor (IGBT) modules. Their dynamic performance is influenced by the gate driver control, operating points and the switching loop parasitics, which are crucial to their optimized operational behaviours, efficiency and field reliability. This paper investigates the controllability of the transient voltage and current slopes of megawatt IGBT modules during their turn-off transitions and proposes an efficient assessment method accordingly. Firstly, the causal relationship of transient characteristic variations and controllability is investigated analytically. Then, major factors impacting the controllability are analysed and validated, including the charge carrier profile, the operating points (i.e. the load voltage, the load current, and the junction temperature), and the gate resistance. Finally, an efficient method using the MOS-channel turn-off point on calibrated gate voltage waveform is proposed for the controllability evaluation, which can guide the IGBT, gate driver, and converter design