Hitachi, Ltd.

Takayuki Matsui

Toshiaki Okuyama

Noriyoshi Takahashi

Kazuo Tahara

Haruo Koharagi

Eiichi Toyota

Junichi Takahashi

Akira Horie

Yuzuru Kubota

Seizi Yamashita

Yoshio Tsutsui

Syuuji Saitoo

Takeshi Ando

Hisaya Sasamoto

Masato Suzuki

Kazuaki Tobari

Kiyoshi Nakamura

Kiyoshi Nakata

Masami Ito

Tokunosuke Tanamachi

Mitsugu Matsutake

Mutsuhiro Terunuma

Shoji Motegi

Seiji Yamashita

Noboru Fujimoto

Syuuji Saitou

Takashi Sukegawa

Kazuo Tohara

Akira Takemura

A power converter including a snubber circuit which is smaller and regenerates more energy than a conventional snubber circuit. A plurality of self-quenching semiconductor switching elements are connected in series across a power supply. A capacitive element is connected to the switching elements, and is charged to more than the voltage of the power supply by a snubber action due to operation of any of the switching elements. The charge stored in the capacitive element is then regenerated to the power supply. The capacitance of the capacitive element can be almost as small as a minimum required capacitance, and can be as small as one-tenth of the capacitance required in a conventional snubber circuit, thereby providing a power converter which is smaller and has a smaller snubber loss than a conventional power converter.

Power converter

Disclosed is an apparatus for realizing a small apparatus by making element currents uniform in the dipolar modulation mode. The zero voltage period in the dipolar modulation period is made shorter than other voltage output periods. Accordingly, currents of switching elements constituting the main circuit of an inverter can be made uniform.

Control apparatus of power converter and control apparatus of electric

A parallel multi-inverter system including a plurality of inverters connected in parallel to each other through one or more parallel reactors, wherein output voltages of the inverters are controlled on the basis of the polarity of an output voltage command signal and a comparison result between a value obtained by converting the output voltage command signal into a positive one and a carrier signal to reduce harmonic components of the line-to-line voltages, and further two different switching modes to set the output voltage of the system zero are equally used to prevent a circulating current from flowing through the parallel reactors during each zero potential period of the output voltage of the system.

Parallel multi-inverter system and motor drive system using the same

A converter circuit includes three-phase unit converters connected in cascade in two stages for supplying electric power to a load. In a region in which the converter output voltage ratio is small, the firing phases of both converters are so set that a phase difference of 120.degree. makes appearance therebetween, while in a region in which the converter output voltage ratio is large, the firing phases are so set as to have a phase difference of 60.degree. therebetween, whereby an angular difference of 90.degree. to 30.degree. is caused to occur constantly between the phases of voltage ripple components of the unit converters. Power factor of a power supply source is improved while ripple in the output voltage of the converter circuit is reduced.

Control apparatus for cascaded converter circuit

A vector control system for an induction motor driven by a power converter which generates three phase ac currents containing harmonics. In the system, an exciting current command value and a torque current command value in a rotating magnetic field coordinate system are applied, induction motor primary currents in a stator coordinate system is detected at a period which is the same or integral multiple of that of the harmonic components by integration operation, the detected value of the integrated primary currents is subjected to definite integration over the same time interval as the period thereof thereby detecting fundamental wave components of the primary currents without the harmonic components, the fundamental wave components are transformed in the form of rotating magnetic field coordinate system thereby detecting an exciting current component and a torque current component, a deviation between the exciting current command value and the detected actual exciting current component and a deviation between the torque current command value and the detected actual torque current component are detected respectively, and producing and applying to the power converter three phase ac voltage command values in the stator coordinate system tending to reduce the deviations to zero.

Vector control system for induction motors

A current-circulating cycloconverter includes a positive converter and a negative converter connected in anti-parallel with each other through a DC reactor. A load is connected to an intermediate tap of the DC reactor. When a load current flowing to the load is smaller than a predetermined value, a circulating current flowing through the positive and negative converters is held at a minimum required value. A circulating current is caused to additively flow for canceling a voltage drop produced across the DC reactor when the load current exceeds the predetermined value.

Method and apparatus for controlling circulating-current type

In induction motor driven by a voltage-type inverter, the torque current component is determined by detecting a primary current flowing to the induction motor. On the basis of the torque current component determined, the output voltage and frequency of the voltage-type inverter are controlled. Additionally, the rotational speed of the induction motor is estimated on the basis of the detected torque current component and the speed of the induction motor is controlled such that the estimated speed signal coincides with a speed command signal.

Method of controlling inverter-driven induction motor

A novel armature of an electric rotating machine is disclosed. The armature core is divided axially into two or more members. The coils of the armature winding are fixed on the armature core in such a way that two or more coil sides are disposed in each slot of one member, and the coil sides disposed in the same slot are arranged in adjacent different slots of the other member. The end of each coil is positioned in a manner to substantially equalize the mutual inductance between each pair of adjacent coil ends.

Armature of rotating machine with means to balance the mutual inductance

The first and second interpole compensation windings are disposed on the commutation starting side and the commutation ending side of the interpole cores, respectively. The current flowing through the first and second interpole compensation windings are controlled in response to the first and second voltages detected by the first and second brushes disposed on the commutation starting side and the commutation ending side of the brushes.

D.C. Rotary machine with interpole compensation

In a stator provided with interpoles, a magnetic flux adjusting winding is provided adjacent to the radially inner end of each interpole core for adjusting the magnetic flux passing through the half of the circumferential width of the interpole core, so that the intensity of the magnetic flux passing through the radially inner end of the interpole core becomes substantially uniform along the end face of the interpole core, whereby the waveform of the commutating emf is simulated to that of the reactance voltage to widen the width of the no-spark zone during commutation thereby improving the commutation performance without appreciably modifying the original shape or structure of the stator.

Stator of D.C. rotary machine

At least one circumferential slot is provided at a predetermined axial position on an armature core so as to cross axial slots receiving a plurality of coil sides of an armature winding and to communicate adjacent axial slots, and the plurality of coil sides to be generally mounted in the same axial slot are partially shifted from one slot to an adjacent one through the circumferential slot so that the coil sides of the armature winding are partially arranged to extend through adjacent slots at a fixed, predetermined circumferential distance. In this manner, the generation of commutating spark is substantially prevented and the commutating performance is improved.

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Hitachi, Japan

Takayuki Matsui