Abstract: A crack detection device for detecting a crack that occurs in a structure, includes: an MI cable that includes a metal sheath and a conductive wire accommodated in the metal sheath via a mineral insulating powder, and that is disposed along the structure so as to intersect an assumed crack C in a part of the structure where occurrence of a crack is assumed; a joint portion that is made of a metal that forms a joint when solidified from a melting state, and that joins the MI cable to the structure or a member fixed to the structure; and a detection device connected to both ends of a conductive wire, and configured to detect electrical characteristics of the conductive wire. The joint portion is present on one side and the other side with respect to the assumed crack C in a direction intersecting the assumed crack C.

Abstract: A crack detection device for detecting a crack that occurs in a structure, includes: an MI cable that includes a metal sheath and a conductive wire accommodated in the metal sheath via a mineral insulating powder, and that is disposed along the structure so as to intersect an assumed crack C in a part of the structure where occurrence of a crack is assumed; a joint portion that is made of a metal that forms a joint when solidified from a melting state, and that joins the MI cable to the structure or a member fixed to the structure; and a detection device connected to both ends of a conductive wire, and configured to detect electrical characteristics of the conductive wire. The joint portion is present on one side and the other side with respect to the assumed crack C in a direction intersecting the assumed crack C.

Abstract: A power conversion device includes a converter that converts AC power to DC power, a converter controller that controls an output voltage of the converter, an inverter that converts the DC power to AC power at a variable frequency, an inverter controller that controls an output frequency of the inverter, and a current detector that detects an AC current on an input side of the converter. It is configured in such a manner that the inverter controller adjusts a slip frequency of the induction motor in response to a fluctuation of the AC current on the input side of the converter detected by the current detector. It thus becomes possible to suppress a beat current in an output current of the inverter at the occurrence of a load fluctuation as well as a power supply voltage fluctuation.

Abstract: A power conversion device includes a converter that converts AC power to DC power, a converter controller that controls an output voltage of the converter, an inverter that converts the DC power to AC power at a variable frequency, an inverter controller that controls an output frequency of the inverter, and a current detector that detects an AC current on an input side of the converter. It is configured in such a manner that the inverter controller adjusts a slip frequency of the induction motor in response to a fluctuation of the AC current on the input side of the converter detected by the current detector. It thus becomes possible to suppress a beat current in an output current of the inverter at the occurrence of a load fluctuation as well as a power supply voltage fluctuation.

Abstract: A control device for an electric vehicle having a reverse L type first filter circuit composed of a first filter reactor and a first filter capacitor between a current collector and control means for controlling electric motor of the electric vehicle. A second filter circuit composed of a series connected second filter reactor and a second filter capacitor is connected in parallel to the first filter capacitor. The second filter circuit has circuit constants selected such that a composite impedance of the second filter circuit and the first filter capacitor when viewed from the control means becomes small at a specific frequency.

Abstract: A braking system for an electric railcar having an a.c. motor with a variable voltage variable frequency inverter. The inverter controls the voltage and frequency supplied to the a.c. motor in response to the railcar speed, commands from the cab, load conditions, etc. The braking system also includes a pneumatic brake which operates at low speeds. A control circuit operates the inverter to supply electric braking down to a slow speed and then simultaneously applies electric braking and pneumatic braking, smoothly increasing the pneumatic braking force until the railcar stops. During the transistion from electric braking to pneumatic braking the control circuit maintains an output frequency from the inverter to the a.c. motor in the vicinity of 0 Hz, keeping the voltages in the positive phase range.

Abstract: A protection circuit for preventing an over-current condition if the semiconductor power controller in an electric train power control circuit is defective. The power controller is connected in series through first and second switches to a D.C. power source. A capacitor is also connected to the power source through the two switches and through a charging resistor connected in parallel with the second switch. When the first switch is closed, the capacitor is charged through the first switch and the resistor. After the capacitor voltage reaches a set reference voltage during a predetermined time interval, the second switch is closed to permit the power control equipment subsequently to apply power to the driving motor of the train. If the capacitor voltage does not reach the reference voltage during the predetermined time interval, then the second switch remains open and the first switch is re-opened to completely disconnect the power control equipment from the D.C. power source.

Abstract: An electric vehicle monitoring system in which one induction motor has a rotational speed detector but another motor does not have such a detector. Separate current detectors monitor the current delivered to each of the motors. A calculations circuit uses the rotation of the one motor and a comparison of the two currents to monitor the performance of both motors.

Abstract: An inverter for use with a vehicular induction motor employs a modulation system in which the waveform of the carrier wave is adjusted so that the modulation wave is made into a constant DC signal.