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The electrical power system in ships can be traced to the 1880s, when lightbulbs were installed on SS Columbia. Since then, electricity has been a crucial part of marine vessels. Research and development initiatives resulted in innovations including the ac motor and transformer, turboelectric power, submarines, dieselelectric propulsion, modern solidstate power electronics, the use of liquified natural gas (LNG) as fuel, and pure electric and hybrid ferries with pluggedin and wireless charging from shore.

This paper presents monitoring of ageing in high power insulated gate bipolar transistor (IGBT) modules subjected to sinusoidal loading at nominal power level. On-state voltage for IGBT, diode, and rise in interconnection resistance are used as ageing parameters. These are measured in three different ways: calibration of power modules after 24 h of operation, offline characterization every 5 min of operation, and continuous measurement during normal converter operation. Four power modules are tested, which are cycled to different degradation levels by number of cycles, where one is tested until failure. The characterization at different stages of lifetime indicates that the rise in resistance originates from thermo-mechanical degradation of interconnects. Post-test investigations: four-point probing and micro-sectioning indicate thermo-mechanical induced degradation of the chip topside interconnects as the source for rise in resistance. Major degradations are observed in bond wires and metallization on the low side diode.

Power semiconductor devices are the most fragile components limiting reliability of power converters, where major stresses are temperature dependent parameters. Typically, the operating virtual maximum junction temperature is specified by a manufacturer for each individual device. The thermal system and operating load are designed based on this number. Online monitoring of an on-state collector–emitter voltage (υce,on) and a junction temperature is necessary to ensure the design performance within a safe limit and also to make this method applicable for derating/uprating power. This paper presents the real time measurement of υce,on and thereby the junction temperature estimation in high power converters. Knowing these parameters online, the maximum power capability can be detected. The operating maximum junction temperature is selected and thereby based on the operating condition the derating of power is shown for a megawatt (MW) converter. An experimental setup including online monitoring is described and the measurement of power derating is presented at the specified conditions.

The paper describes the selection of Nepalese timber for development of small wind turbine blades on the basis of locally based low cost timbers, along with the selection of coatings to protect the timber from weathering. The selection criterion of timber includes timber mechanical properties, weathering effect on coatings, price, growth and availability of the timber. Mechanical properties such as Young's modulus of elasticity, breaking strength, breaking strain and Brinell's hardness of selected Nepalese timbers are presented. The effects of weathering on timbers without coating, and with different coatings, are analysed on the basis of the change in weight of the timber due to the effect of humidity and rainfall over a period of nineteen months. Degradation of different coatings of timber are compared.

Power density is a key performance factor in order to reduce the cost and size of a power converter. Because of the unknown junction temperature, today’s design margins are relatively high to ensure safe and a reliable operation. In this paper, the on-state voltage drop is measured online for all insulated gate bipolar transistors (IGBTs) in the inverter, using advanced gate driver. The die temperature is estimated and monitored on each device during power converter operation. Based on the monitored temperature in real time, the maximum power capability is detected. The output power is increased until a safe operating temperature of power modules. This enable a power density is increased by 11.16 kW/litre to 19.13 kW/litre in a low voltage power stack which is typically used in wind power converters. Experiment results are shown for safe operation of converter at around 1.2 MW, which is built in a standardsize for the 600 - 700 kW. Furthermore, the 1700 V, 1000 A power module is replaced with a 1400 A module to increase the load current.

Mission profile data provides useful data for a cost effective and reliable design of future power converters. The development of a field data logger using a Raspberry Pi (RBPI) and temperature and humidity sensors is presented. The collected data is analyzed and classified for the purpose of data reduction. Key parameters used in Arrhenius and Coffin-Manson equations are computed continuously using the collected data. In addition the rain-flow cycle count algorithm is implemented to record cyclic temperature variations. The prototype has been installed in an inverter for photovoltaic generation and the collected data are presented here.

Mission profile data is very important for the cost effective and reliable design of power converters. The converter design can be improved on the basis of actual field data. Actual mission profile data can be collected for the power converters using field data loggers over a long period of time and subsequent analysis of the data. This paper presents the development of a low cost prototype field data logger prototype using Raspberry PI and industrial sensors. The functionalities of the data logger prototype are described. An online rainflow count algorithm has been implemented as well.

The real-time junction temperature monitoring of a high-power insulated-gate bipolar transistor (IGBT) module is important to increase the overall reliability of power converters for industrial applications. This article proposes a new method to measure the on-state collector?emitter voltage of a high-power IGBT module during converter operation, which may play a vital role in improving the reliability of the power converters. The measured voltage is used to estimate the module average junction temperature of the high and low-voltage side of a half-bridge IGBT separately in every fundamental cycle of the current by calibrating them at load current. The measurement is very accurate and also measures the voltage at the middle of a pulse-width modulation (PWM) switching. A major objective is that this method is designed to be implemented in real applications. The performance of this technique is measured in a wind power converter at a low fundamental frequency. To illustrate more, the test method as well as the performance of the measurement circuit are also presented. This measurement is also useful to indicate failure mechanisms such as bond wire lift-off and solder layer degradation. The measurements of and rise in the junction temperature after five million cycles of normal operation of the converter are also presented.

An on-state collector-emitter voltage (V ce ) measurement and thereby an estimation of average temperature in space for high power IGBT module is presented while power converter is in operation. The proposed measurement circuit is able to measure both high and low side IGBT and anti parallel diode voltages for a half bridge module which are also used to monitor the electrical degradation of the module. The V ce load current is proposed to estimate the variation of average temperature in space at every fundamental cycle of sinusoidal loading current. Initially, the calibration of voltage and junction temperature for load current level is presented and a trend of change in calibration factor for the IGBT is presented. Finally, the variation in temperature for sinusoidal variation of current is presented at initial stage and after an ageing of the IGBT. The measurement technique is simple and easy to implement into a gate driver for field applications.

A real time on-state collector-emitter (Vce) voltage monitoring is sensitive due to a stray inductance and a parasitic capacitance inside high power IGBT modules. An additional circuit used to monitor the on-state Vce introduces small current into the module. Though the current is low in comparison to the converter current, the effect on gate driving signals cannot be neglected during worst case switching operations. The worst case situation is occurred during turn-on and turn-off period of the switches at low on-time of the IGBT. Furthermore, during this period, when the common terminal of the measurement circuit is not in contact properly, the consequences of the error will be higher by deteriorating the gate driving signals. This type of error may occur due to the vibration or during implementation of the measurement circuit in the converter. This paper presents the influence of the error into the measurement and shows the measurement of current and voltage transients during the converter operation. The selection of the components for the measurement circuit is also discussed. The effect in gate driving signals with and without the error events are presented. Finally, a real time Vce measurement of IGBT module in the converter operation is presented.

Insulated Gate Bipolar Transistors (IGBTs) are key component in power converters. Reliability of power converters depend on wear-out process of power modules. A physical parameter such as the on-state collector-emitter voltage (Vce) shows the status of degradation of the IGBT after a certain cycles of operation. However, the Vce mainly shows the wear-out of bond wire lift-off and solder degradation. The Vce is normally used to estimate the junction temperature in the module. The measurement of Vce is sensitive to the converter power level and fluctuations in the surrounding temperature. In spite of difficulties in the measurement, the offline and online Vce measurement topologies are implemented to study the reliability of the power converters. This paper presents a review in wear-out prediction methods of IGBT power modules and freewheeling diodes based on the real time Vce measurement. The measurement quality and some practical issues of those measurement techniques are discussed. Furthermore, the paper proposes the requirements for the measurement and prognostic approach to determine wear-out status of power modules in field applications. The online Vce measurement for a selected topology is also shown in the paper.