Akihiro Imakiire

Comparison performance of Si-IGBT and SiC-MOSFET used for high efficiency inverter of contactless power transfer system

This paper deals with investigation on electrical characteristics of both conventional Si-IGBT and next generation power semiconductor device SiC-MOSFET for high efficiency inverter of contactless power transfer system. This system has an issue that the power conversion efficiency is lower than that of conventional charging system using a plug. Since a proto type contactless power transfer system that we evaluated before adopted Si-IGBT, higher power conversion efficiency has been required. Thus, an attempt is made to improve the inverter efficiency using SiC-MOSFET. The performance of Si-IGBT and SiC-MOSFET are evaluated by conducting a switching test and experiment of static characteristics. Furthermore, inverter loss is calculated and discussed using experimental results of Si-IGBT and SiC-MOSFET. As a result, the inverter efficiency is found to increase by 0.48% using SiC-MOSFET. Additionally, it is suggested that ringing of the voltage and current should be suppressed when SiC-MOSFET is applied to an inverter for high frequency application like a contactless power transfer system.

Investigation of calculation method of losses in PWM inverter with voltage booster using both DC link voltage Control and flux weakening control

In this paper, authors investigate calculation method of losses in system which consists of interior permanent magnet (IPM) motor and PWM inverter with voltage booster. This system has two driving methods for motor in high speed region. One is DC link voltage Control. The other is flux weakening control. However, it is not cleared how combination of these two control methods is suitable for this system. It is necessary to quantitatively estimate parts of system losses in voltage booster, inverter and IPM motor, because total efficiency of system is decided by parts of system losses. So, the simulation model, which is capable of calculating parts of system losses to find suitable driving method for IPM motor using combination of the two control methods, is introduced and simulation results are discussed.

Characterization of contactless power transfer system and investigation of core shape for AGV application

In recent years, the introduction of contactless power transfer (CPT) system is required to automated guided vehicle (AGV) used in a factory. This paper deals with development of prototype contactless power transfer system for applying to AGV using both experiment and simulation. It is found that the developed prototype contactless power transfer system allows 1 kW power transfer in more than 68% of power transfer efficiency at 20 mm gap. Furthermore, an attempt is made to optimize the CPT by changing the core shape of the coils. As a result, combination of T-T shape cores made of ferrite core allows transmission of more power than T-E combination cores. These results suggest that the T-T shape cores contribute to further miniaturization of CPT system and larger capacity than previous CPT system using T-E combination cores.

Proposal of PM motor driving system consist of PWM inverter with voltage booster for applying to automated guided vehicle

This paper deal with a proposed PM motor driving system consist of PWM inverter with voltage booster to apply to wireless power transfer system for automated guided vehicle (AGV). This system would provide advantage that it makes to drive a PM motor and charge a battery at high efficiency against conventional system using low voltage battery because DC link voltage controlled by voltage booster at more high voltage. In addition, the voltage booster takes two roles such as DC link voltage control and battery current control. Therefore, circuit configuration can be simplified. Furthermore, the effectiveness of using SiC-MOSFET for the proposed system is suggested by evaluating efficiency of the prototype inverter by experiment. As above the investigation, it was cleared that the effectiveness of proposed PM motor driving system add the function of wireless power transfer for AGV.

Investigation of prototype SiC power module structure for low inductance and high heat operation

This paper deal with structure for low inductance and high heat operation of silicon carbide (SiC) power module, which attracts attention in terms of high withstand voltage, high efficiency and high heat operation in recent years. First, the parasitic inductance of the power module of two types of structure; a conventional structure which forms the current path in a planar manner and a structure formed three-dimensionally is investigated using electromagnetic field analysis. In addition, thermal resistance of two types of power modules are experimentally evaluated from heat radiation performance. Experimental and simulated results reveals that the three-dimensionally formed power module is superior in the current path, resulting in lower parasitic inductance as well as smaller switching loss. Moreover, on state resistance and leakage current are evaluated at the junction temperature of 250 °C and the problems of power module package under high temperature environment is also investigated.

Experimental verification of operation and method of decision of maximum DC link voltage in wireless power transfer system

This paper deals with a developed system that allows to drive an induction motor and charge a battery using wireless power transfer (WPT) for automated guided vehicle (AGV). The developed system enables to control output voltage of WPT by constantly moving the receiving coil and adjusting the gap length. It is desired that the system should withstand high voltage, and reduce copper loss and conduction loss in coil and power conversion circuits, respectively, to achieve high efficiency for the system. However, methods for determining the output voltage in the WPT system for AGVs has not been investigated yet. From the viewpoints, we investigate the allowable maximum output voltage provided by the developed WPT system. The maximum voltage is calculated using control equations including parameters of voltage booster, power supply voltage and battery current when the battery current control is adopted. Furthermore, experimental results reveal that the battery current control cannot be used beyond a maximum DC link voltage. In addition, a properly selected gap length of the coil is found to allow an induction motor to be driven and the battery to be charged using the WPT system. As a result, it is clarified by the experiments that the developed control system provides additively effective function to WPT for AGVs.

Partial discharge inception voltage of pressurized gas insulation encapsulation used for high-temperature and high-voltage power module

This paper deals with the gas pressure and temperature dependence of partial discharge inception voltage (PDIV) of a developed gas-insulated power module as a high temperature and high voltage package. Increasing the gas pressure and temperature in the developed power module increases and decreases PDIV, respectively. Furthermore, the result of decreasing PDIV with increasing temperature is discussed by taking PD light emission image and simulating electrical field around the contact between a springs electrode and Si3N4 dielectric chip which simulates SiC-SBD.

Evaluation of partial discharge inception voltage of bonding-less gas insulation packaging for high temperature and high voltage power module

The purpose of our work is to develop a power module using gas insulation and bonding-less interconnections to avoid the reliability issues known to current packaging technology. This paper deals with the temperature dependence of partial discharge inception voltage (PDIV) of a developed module up to 300 °C. In addition, an attempt is achieved to confirm half-wave rectifying operation up to 300 °C using SiCSchottky barrier diodes (SiC-SBD). From these results, the PDs were not detected up to 1500 V and 300 °C, proving its ability to be used in high temperature applications.