Fuji Electric Co., Ltd.

Fuji Electric Systems Co. Ltd.

Hitachi, Ltd.

Fuji Electric Fa Components & Systems Co., Ltd.

Nagaoka University of Technology

Akihiro Odaka

Akio Toba

Masakazu Gekinozu

Yasuhiro Tamai

Ikuya Sato

Junichi Itoh

Hidetoshi Umida

Masaki Hirakata

Shinichiro Adachi

Kouetsu Fujita

Kousuke Itou

Koroku Nishizawa

Akihiro Imakiire

An object of the present invention is to provide an MRI apparatus capable of optimally setting imaging conditions for map measurement depending on a target value and its required accuracy, and a method for controlling the MRI apparatus. An imaging unit of the MRI apparatus includes, as a pulse sequence, a pulse sequence for the T1 map measurement that includes a first signal acquisition sequence and a plurality of signal acquisition sequences executed after application of an inverted pulse and at different signal acquisition times from the inverted pulse. An imaging controller of the MRI apparatus controls the imaging conditions of each of the plurality of signal acquisition sequences, for example, the signal acquisition time from the inverted pulse and the number of signal acquisition sequences depending on the T1 value of an imaging target and the required accuracy.

Magnetic resonance imaging apparatus and method for controlling the same

A power conversion device, that includes a drive circuitthat drives a switching elementincluded in an upper-arm for one of three phases, a drive circuitthat drives a switching elementincluded in a lower-arm for the one phase, and a control circuitthat transmits a control signal to the drive circuits, is provided. The power conversion device includes power supply circuitsthat provide power to the drive circuits, respectively, a low-voltage power supplythat supplies power to one of the power supply circuits,, and a high-voltage power supplythat supplies power to the other of the power supply circuits,. Accordingly, it is possible to reliably protect a system: by realizing minimal redundancy of the power supply, the power supply generation circuit, etc.; and by realizing the short-circuit mode at the time of error occurrence.

Power conversion device

A three-phase inverter includes three series circuits that are connected in parallel to a capacitor connected in parallel to a DC voltage source. Each of the three series circuits includes two semiconductor switching elements connected in series. A connection point between the two semiconductor switching elements is used as an AC output terminal for each phase. The three-phase inverter generates PWM pulses of three phases including a PWM pulse of one phase, whose pulse width of a positive side pulse in one switching cycle is the largest, and including PWM pulses of the other two phases such that a positional relationship between positive side pulses of the other two phases is a positional relationship in which an overlapping range on a time axis is smaller as compared with a state in which a positive side pulse of one phase encompasses a positive side pulse of the other pulse.

Three-phase inverter with reduced DC bus capacitor ripple

A control method of an inverter for outputting polyphase alternate-current electrical power is provided. In the control method, modified PWM pulses of respective phases for controlling semiconductor switching elements of the inverter are generated, based on an output of a counter common to the respective phases. Each of the modified PWM pulses is configured such that a total pulse width, in a period corresponding to one or more cycles of a carrier, is substantially equal to a total pulse width of an assumed PWM pulse which is obtained by comparing, with the carrier, a time average value of an output voltage of the corresponding phase in the period. Further, at least one of a generation timing and a generation frequency of at least one of the modified PWM pulses is changed from the assumed PWM pulse.

Inverter that adjusts voltage command values and control method of inverter

A semiconductor chip temperature estimation device that estimates the temperature of a semiconductor chip incorporated together with a thermistor in a semiconductor module includes a first estimation unit which calculates a first estimation value of a chip loss of the chip, a memory which stores in advance a correlation between a temperature rise of the temperature sensor and the chip loss of the chip, a second estimation unit which calculates a second estimation value of the temperature rise of the temperature sensor, and a third estimation unit which calculates a third estimation value of the temperature of the cooling element. The temperature of the semiconductor chip is estimated by using the third estimation value as a base temperature.

Semiconductor chip temperature estimation device and overheat protection device

A method for a power conversion apparatus to drive an electric motor using a power semiconductor device. The method includes detecting or estimating a temperature of the power semiconductor device to thereby obtain a detected or estimated temperature value, adjusting a torque command of the electric motor, so that the temperature of the power semiconductor device matches a preset temperature when the detected or estimated temperature value is equal to or higher than the preset temperature, and controlling the power semiconductor device using the adjusted torque command.

Power converter

With a power conversion device, it is possible to lengthen the lifespan of a mechanical switch by preventing an absorption by the mechanical switch of induction energy accumulated in a reactor when there is a problem. When a mechanical switch is turned off when there is a problem, an absorption by the mechanical switch of induction energy accumulated in a reactor is prevented by the energy accumulated in the reactor being released to a capacitor via a diode, thus enabling a lengthening of the lifespan of the mechanical switch.

An electric power supply system for driving an electric rotating machine has a generator supplied with driving power from an engine to generate alternating-current electric power and a matrix converter as an alternating-current to alternating-current direct converter supplied with the alternating-current electric power to output arbitrary alternating-current electric power. By driving a motor with the alternating-current electric power supplied from the matrix converter, only one time electric power conversion is carried out to provide high efficiency in the whole system. In addition, electric power loss can be reduced so as to enhance a motor output when the system is applied to a vehicle power supply system.

Power supply system for driving electric rotating machine

A power converter directly converting an AC voltage into an AC voltage of any desired magnitude and frequency by turning bidirectional switches ON and OFF without employing any energy buffer, where the peak values of output phase voltage command values are limited, to bring the amplitude of an output line voltage to, at most, 0.866 times the amplitude of the supply line voltages. By way of example, the peak-value limit of the output phase voltage command values is set so that the maximum value of the output phase voltage command values becomes, at most, 0.75 times the maximum value of supply phase voltages, while the minimum value thereof becomes, at least, 0.75 times the minimum value of the supply phase voltages. This control method for the direct power converter dispenses with an expensive dedicated motor, and permits a reduction in cost of the control apparatus as a whole.

Control method for direct power converter

A motor driving apparatus drives a motor by means of an AC/AC direct converter such as a matrix converter. The motor driving apparatus is provided with a current detecting section for detecting motor currents, a comparing section for detecting whether motor current detection values have exceeded a restriction level, an induction voltage calculating section for calculating induction voltages of the motor, a switching section, and a PWM pattern generating section. When the comparing section detects that the motor current detection values have exceeded the restriction level, the switching section supplies the induction voltages calculated by the induction voltage calculating section to the converter as output voltage instruction values.

Motor driving apparatus

Method and apparatus for controlling a DC-DC converter change the switching frequency of the switching devices and the on-off ratio of the switching devices. The on-off ratio can be changed in response to the output voltage and the switching frequency can be changed in response to the input voltage supplied by the DC power supply. Alternatively, the switching frequency can be changed while the on-off ratio is fixed at a certain value, and the on-off ratio can be changed while the switching frequency is fixed at a predetermined value after the switching frequency has reached the predetermined value, thereby preventing the switching frequency from exceeding the predetermined value.

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Tokyo, Japan

Akihiro Odaka