Abstract: A converter includes a converter circuit 1 having a plurality of bridge-connected semiconductor switching devices for converting AC power into DC power, a smoothing condenser connected in parallel to the DC side of the converter circuit and a current detector provided in a condenser circuit to control a condenser current flowing through the smoothing condenser to be a set value. The condenser current is controlled to be the set value (e.g. zero) to thereby reduce the capacity of the smoothing condenser and make the converter small.

Abstract: A converter includes a converter circuit 1 having a plurality of bridge-connected semiconductor switching devices for converting AC power into DC power, a smoothing condenser connected in parallel to the DC side of the converter circuit and a current detector provided in a condenser circuit to control a condenser current flowing through the smoothing condenser to be a set value. The condenser current is controlled to be the set value (e.g. zero) to thereby reduce the capacity of the smoothing condenser and make the converter small.

Abstract: A converter includes a converter circuit 1 having a plurality of bridge-connected semiconductor switching devices for converting AC power into DC power, a smoothing condenser connected in parallel to the DC side of the converter circuit and a current detector provided in a condenser circuit to control a condenser current flowing through the smoothing condenser to be a set value. The condenser current is controlled to be the set value (e.g. zero) to thereby reduce the capacity of the smoothing condenser and make the converter small.

Abstract: An inverter device for variably controlling an operating frequency of an electric motor, which drives a compressor in a refrigerating cycle. the inverter includes a box-like resin case, having a metal film for shielding being applied or plated on a surface thereof and having a step portion on which a terminal block for the motor is arranged. A first substrate having mounted thereon power semiconductor devices constituting a converter and an inverter so as to be immersed in gel, and the first substrate is mounted in the case and brought into proximity of radiation fins at a reverse surface thereof. A second substrate having mounted thereon interface connectors into which signals from detection sensors for temperatures and pressures in the refrigerating cycle are input and photo-couplers for transmitting the input signals, and the second substrate is mounted in the case above the first substrate.

Abstract: A converter includes a converter circuit 1 having a plurality of bridge-connected semiconductor switching devices for converting AC power into DC power, a smoothing condenser connected in parallel to the DC side of the converter circuit and a current detector provided in a condenser circuit to control a condenser current flowing through the smoothing condenser to be a set value. The condenser current is controlled to be the set value (e.g. zero) to thereby reduce the capacity of the smoothing condenser and make the converter small.

Abstract: A refrigerating apparatus having a refrigerating cycle that comprises a compressor, an electric motor that drives the compressor, and an inverter device that variably controls the operating frequency of the electric motor. The inverter device includes a converter circuit that converts an A.C. voltage from an A.C. power supply into a D.C. current, an inverter circuit comprising a D.C./A.C converter, and a shunt resistance that detects a D.C. current flowing through a switching element of the inverter circuit. The shunt resistance detects a D.C. current, and the detected D.C. current value is calculated as a sine wave A.C. current for the electric motor in relation to action of the switching element.

Abstract: An inverter device for variably controlling an operating frequency of an electric motor, which drives a compressor in a refrigerating cycle. the inverter includes a box-like resin case, having a metal film for shielding being applied or plated on a surface thereof and having a step portion on which a terminal block for the motor is arranged. A first substrate having mounted thereon power semiconductor devices constituting a converter and an inverter so as to be immersed in gel, and the first substrate is mounted in the case and brought into proximity of radiation fins at a reverse surface thereof. A second substrate having mounted thereon interface connectors into which signals from detection sensors for temperatures and pressures in the refrigerating cycle are input and photo-couplers for transmitting the input signals, and the second substrate is mounted in the case above the first substrate.

Abstract: A refrigerating apparatus comprises: a first substrate, on one surface of which an active converter and an inverter are mounted, and on a reverse surface of which a radiation fin is closely fixed; a second substrate, on which a microcomputer, a current detecting mechanism, and a terminal block are mounted; a resin casing covering sides of the first and second substrates and provided with a step permitting the terminal block to be arranged thereon; and a third substrate, on which an interface connector and a photo-coupler are mounted. The first substrate, the second substrate, and the third substrate are layered in this order on a bottom surface of the casing. Gel is filled up to a power semiconductor surface of the first substrate, and a resin is filled up to an upper surface of the second substrate.

Abstract: In detecting an output current of a power converter based on a DC current Idc of the power converter, the pulse width of the DC current Idc becomes narrower when the pulse width of a line voltage is narrower, and its detection becomes difficult. A voltage command correction unit 9 according to the present invention corrects voltage commands such that pulse width of a line voltage becomes zero when the pulse width of the line voltage is less than the minimum pulse width, not to output a line pulse, and an error generated by the correction is integrated. This integrated error is added to the line voltage in the next time, and the integrated pulse width of the line voltage is outputted when the pulse width becomes larger than or equal to the minimum pulse width.

Abstract: A refrigerating apparatus comprises: a first substrate, on one surface of which an active converter and an inverter are mounted, and on a reverse surface of which a radiation fin is closely fixed; a second substrate, on which a microcomputer, a current detecting mechanism, and a terminal block are mounted; a resin casing covering sides of the first and second substrates and provided with a step permitting the terminal block to be arranged thereon; and a third substrate, on which an interface connector and a photo-coupler are mounted. The first substrate, the second substrate, and the third substrate are layered in this order on a bottom surface of the casing. Gel is filled up to a power semiconductor surface of the first substrate, and a resin is filled up to an upper surface of the second substrate.

Abstract: The present invention provides a control algorithm which instantaneously detects magnetic pole positions in the inside of a motor including polarities of the motor. A controller 1 applies a minute voltage change vhd to a voltage command on a dc axis which constitutes an estimation magnetic pole axis of the motor 3, detects electric currents Idc, Iqc of a motor 3 and discriminates the polarities of the magnetic pole axes by making use of the difference between a cycle in which ripple components of the electric currents Idc, Iqc become positive and a cycle in which the ripple components become negative or the difference between positive-side and negative-side current change rates. Further, the minute voltage change vhd with respect to the above-mentioned voltage command is generated on both of the dc axis and the qc axis rectangular thereto, and the magnetic pole positions of the motor are directly estimated based on the current ripple components on the respective axes.

Abstract: In detecting an output current of a power converter based on a DC current Idc of the power converter, the pulse width of the DC current Idc becomes narrower when the pulse width of a line voltage is narrower, and its detection becomes difficult. A voltage command correction unit 9 according to the present invention corrects voltage commands such that pulse width of a line voltage becomes zero when the pulse width of the line voltage is less than the minimum pulse width, not to output a line pulse, and an error generated by the correction is integrated. This integrated error is added to the line voltage in the next time, and the integrated pulse width of the line voltage is outputted when the pulse width becomes larger than or equal to the minimum pulse width.

Abstract: The present invention provides a control algorithm which instantaneously detects magnetic pole positions in the inside of a motor including polarities of the motor. A controller 1 applies a minute voltage change vhd to a voltage command on a dc axis which constitutes an estimation magnetic pole axis of the motor 3, detects electric currents Idc, Iqc of a motor 3 and discriminates the polarities of the magnetic pole axes by making use of the difference between a cycle in which ripple components of the electric currents Idc, Iqc become positive and a cycle in which the ripple components become negative or the difference between positive-side and negative-side current change rates. Further, the minute voltage change vhd with respect to the above-mentioned voltage command is generated on both of the dc axis and the qc axis rectangular thereto, and the magnetic pole positions of the motor are directly estimated based on the current ripple components on the respective axes.

Abstract: An alumina fiber structure of a flat shape composed of alumina fibers having an alumina content of at least 65% by weight, the majority of said fibers being oriented substantially in parallel with the flat surfaces of the structure, and a number of fiber strands composed of the same alumina fibers extending inwardly from the flat surfaces of the structure, said structure having a thickness of from 4.8 mm to less than 10 mm, a density of from 0.07 to 0.3 g/cm.sup.3, a tensile strength of at least 0.5 kg/cm.sup.2 and a peeling strength of at least 0.5 kg/m.

Abstract: A carbon fiber-reinforced hydraulic composite material having excellent mechanical strength, workability, and freezing-and-thawing resistance, wherein chopped carbon fibers having a monofilament tensile strength of from 140 kg/mm.sup.2 to 270 kg/mm.sup.2, and a monofilament diameter of from 15 .mu.m to 30 .mu.m are blended as the carbon fibers at a ratio of from 1% to 4% by volume with respect to the entire composite material to bring a flow index of the composite material before its hardening to 120 mm or above.

Abstract: Alumina fiber structures prepared by (i) preparing precursor fibers by spinning a viscous spinning solution containing compounds of metals including aluminum and an organic polymer compound in which the proportion of alumina in the total metals in the solution is at least 65% by weight of alumina when all metals are calculated as their oxides; (ii) laying the precursor fibers into a mat; (iii) applying a lubricant which is a solution of higher fatty acid ester in a hydrocarbon solvent to the fibers either before or after forming the mat; (iv) needling the lubricated mat; and (v) burning the obtained structure to convert the precursor fibers to alumina fibers, possess high tensile strengths and high peel strengths.

Abstract: Cement mortar matrix and product are formed which are reinforced with a resin-impreganted twist-woven (Karami-ori) network of fibers which are oriented in the cement mortar in the direction of the maximum tensile stress yielded by the bending moment.

Abstract: A method for manufacturing a concrete structure such as columns and beams with sufficient reinforcement in the shear strength to be durable against earthquakes, etc. A reinforcing member composed of a fiber-reinforced plastic is applied onto the outer periphery of a concrete structural member by winding the fiber strands around the outer periphery of the concrete structural member while impregnating the fiber material with a resin.

Abstract: An alumina fiber structure of a flat shape composed of alumina fibers having an alumina content of at least 65% by weight, the majority of said fibers being oriented substantially in parallel with the flat surfaces of the structure, and a number of fiber strands composed of the same alumina fibers extending inwardly from the flat surfaces of the structure, said structure having a thickness of at least 10 mm, a density of from 0.07 to 0.3 g/cm.sup.3, a tensile strength of at least 0.5 kg/cm.sup.2 and a peeling strength of at least 0.5 kg/m.