Hitachi, Ltd.

Keijiro Sakai

Hiroshi Fujii

Toshiaki Okuyama

Nobuyoshi Mutoh

Yasuo Matsuda

Kinya Nakatsu

Hiroyuki Tomita

Houng Joong Kim

Akiteru Ueda

Junji Kato

Nobuyoshi Muto

Hitoshi Shibata

Seiji Ishida

Kohji Maki

Kenji Nandoh

Mitsuyuki Honbu

Hisao Tadokoro

Hideki Shimane

Teiichi Furukawa

Ikuo Okajima

Akira Ishibashi

Tsunehiro Endo

Takashi Ikimi

Hiroshi Nagase

Masahiro Hiraga

Yuzuru Kubota

Yuhachi Takakura

Toshio Suzuki

Tunehiro Endo

Motonobu Hattori

Tatsuo Ando

Yuichiro Nagato

Hideo Kimura

Kenji Nantoh

The conventional linear drive apparatus has the problem that in constructing a linear motor of a multiphase structure by connecting a plurality of armature units, the length of the armature becomes longer in proportion to the number of the phases, thus limiting the locations where the apparatus can be installed. The problem is solved by a linear drive apparatus comprising a plurality of armature unitsformed by a magnetic material on which a conductor coilis disposed, and an armature comprising an arrangement of the armature units. The armature unitscomprise a plurality of opposing portions having opposing magnetic pole teeth. The magnetic pole teeth of adjacent opposing portions are arranged in an interdigitated manner. A secondary memberis disposed between magnetic pole teeth of the opposing portions. The armature unitscomprise the coilarranged on opposite sides thereof in an alternating manner.

Linear drive apparatus having cores and coils which are positioned on opposite sides of the cores

A linear motor for generating a linear motion in a linear direction, has a plurality of first members, each of which includes an electromagnetic coil for generating a first magnetic field, and a magnetic core (magnetically permeable) having magnetic surfaces being opposite to each other so that the first magnetic field passes a space between the magnetic surfaces, and a second member arranged in the spaces to be relatively movable linearly with respect to a combination of the first members to generate the linear motion in the linear direction, and including a magnet polarized in a polarizing direction to generate a second magnetic field.

Linear motor and X-Y stage

Linear drive apparatus

An inverter apparatus for converting a DC power converted from an input AC power to an output AC power of a variable frequency and a variable electric power to drive an induction motor at a variable speed. The inverter apparatus includes a rectifying unit, a filter capacitor, an inverter unit having an input connected across the filter capacitor, an input current detector and a gate circuitry for driving the inverter unit. An excitation current detection unit detects an excitation current of the induction motor from an output signal of the input current detector, a gate signal for driving the gate circuitry and a reference phase command. A setting unit sets a limitation level of the excitation current, a torque boost voltage command unit produces a torque boost voltage command, and a torque boost voltage compensation unit changes the torque boost voltage command so that the detected excitation current value is smaller than or equal to the limitation level.

Inverter apparatus

Induction voltage command Em* is obtained from inverter's primary frequency command &ohgr; * and torque boost voltage commander produces torque boost voltage command &Dgr;Vz* in accordance with &ohgr; * while integrator produces reference phase command &thgr;d*. uvw/dq converter detects motor excitation current Id (equivalent of no-load current). Next, deviation of excitation current limitation level command Idmax* and detected Id is inputted to limiter processing unit to produce torque boost voltage compensation value &Dgr;Vc for varying &Dgr;Vz* so that Id is smaller than or equal to Idmax*. Inverted &Dgr;Vz* is set up as a lower limiter value of the limiter processing unit. Next, &Dgr;Vc and &Dgr;Vz* are added to produce final compensated torque boost voltage command &Dgr;Vt* and &Dgr;Vt* and Em* are added to produce q-axis voltage command Vq* of the inverter output voltage.

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 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.

Pulse width modulation method, pulse width modulator and power converter

An inverter device has a three-phase inverter for converting DC electric power into AC power for supplement to an AC electric motor and a control device operatively associated therewith, and the control device includes a phase current detection section for outputting a phase current waveform based on a DC input current and an operational processor section for performing operational processing for control of said inverter device based on the phase current waveform. Thereby, the inverter device can be constructed to be very compact.

Inverter device

An inverter control apparatus includes an instruction calculator which receives a speed instruction and a particular component of a current of a motor to obtain an output frequency instruction and output voltage instructions of an inverter and a current estimator to estimate, according to a reference phase obtained by integrating a current detection value of one phase of an ac motor and an output frequency instruction thereof, currents of other phases of the ac motor. The current estimator includes a uvw/dq converter which converts a fixed coordinate system into a rotating coordinate system, a dq/uvw converter which is connected to the uvw/dq converter and which converts the rotating coordinate system into the fixed coordinate system, and a closed loop to input an output from the dq/uvw converter to the uvw/dq converter. This system can therefore estimate currents of other phases according to the motor current of one phase.

Method of inverter control and apparatus of the same

An inverter corrects an output voltage in accordance with the magnitude of output voltage error due to a dead time and an ON-state voltage drop in power elements so as to energize an AC motor in a manner of single phase alternating current excitation, by calculating an active component of current Iq and a reactive component of current Id from the phase .theta. of an excitation voltage vector and a detected instantaneous current value iu, and by measuring characteristic constants of the motor, including a combined resistance (r.sub.1 +r.sub.2) and a combined leakage inductance (l.sub.1 +l.sub.2), from an excitation voltage command value Vc.sub.1, Id and Iq. The measured values are used as the control constants for a speed sensorless vector control. Further, the resistances r.sub.1, r.sub.2, and a self-inductance L.sub.1, which are control constants, can be obtained based on the component in a primary voltage vector direction of a primary current vector Iq' and the component .pi./2 delayed from the primary voltage vector direction of the primary current vector Id'. In this way, the characteristic constants can be accurately measured without any inverter output voltage sensor.

Method for measuring characteristic constants of alternating current

In a control method and device for an AC motor, when transforming output power of a converter to AC power by an inverter and controlling the AC motor with the AC power, a source current value is determined from the value of an electric variable in the input or output side of the inverter, and the converter is controlled in accordance with the source current value. This makes the source current free from an influence of ripple components. Accordingly, even when the load of the AC motor is fluctuated abruptly, the required AC power can be applied to the converter so as to follow such fluctuations.

Control method and device for AC motor

In spatial vector control of a pulse width modulation (PWM) inverter adapted for variable speed drive of an induction motor, a difference vector between magnetic flux vectors occurring during adjacent sampling periods is generated by synthesizing a zero vector and voltage vectors in such a manner that a resultant voltage vector always includes as a component a minimum unit of a zero vector or a voltage vector, whereby even when the angular speed of rotation of the magnetic flux changes, the switching frequency of the PWM inverter is prevented from decreasing and the current ripple is reduced.

Control method of pulse width modulation inverter and pulse width

A PWM inverter apparatus used for driving an a.c. motor, including an inverter having an output part connected to the a.c. motor and switching elements on-off controlled by a PWM signal. The inverter apparatus also includes a part for receiving, at an interval of a given sampling period, status command information specifying a desired status of a vector of a rotating magnetic flux in the a.c. motor; a part for predicting, on the basis of at least the status command information received at each sampling time, the status of the vector of the rotating magnetic flux which will be produced at a next sampling time; a part for calculating a difference vector between the status of the vector of the rotating magnetic flux specified by the status command information received at a present sampling time and the predicted status of the vector of the rotating magnetic flux which will be produced at a next sampling time; a part for synthesizing the difference vector using selected reference voltage vectors from among a plurality of predetermined reference voltage vectors; and a part for generating a PWM signal for controlling the switching elements of the inverter so as to produce the selected reference voltage vectors.

PWM inverter apparatus for controlling rotating magnetic flux in a.c.

A single phase, full wave diode bridge circuit is connected with a chopper on its DC output side. An output voltage of the chopper is smoothed by a smoothing capacitor and thereafter supplied for a load. A current control apparatus forms a current reference signal which is synchronized with an AC voltage applied to the bridge circuit and has a magnitude corresponding to a current flowing through the load and produces a deviation signal between the current reference signal and an actual AC input current of the bridge circuit. The chopper is controlled in accordance with the deviation signal so that the AC input current follows the current reference signal, whereby the power factor and the waveform of the AC input current in the bridge circuit are improved.

Rectifier control apparatus with improved power factor

An AC motor such as an induction motor or a synchronous motor is driven by a PWM inverter circuit. Power switching elements of the inverter circuit are ignited by PWM pulses resulting from comparison of a carrier wave signal with a sine wave modulation signal at a frequency proportional to a frequency setting signal so as to control the inverter circuit. A current polarity detector detects positive and negative components of a DC current flowing in the input side of the inverter circuit. The frequency setting signal is so corrected as to be decreased when only the positive current component flows in excess of one period of the carrier wave signal or increased when only the negative current component flows in excess of the one period.

Method and apparatus for controlling PWM inverters

A control apparatus for producing a pulse width modulating signal to be used for operation of a PWM inverter wherein a modulating wave of a sinusoidal waveform corresponding to the desired AC output voltage of the inverter is sampled at selected periodical time intervals to obtain a level of the modulating wave at each sampling point and the interval is arithmetically determined between each sampling time point and a time point which appears between the sampling point and the next sampling point and at which time point a virtual triangular waveform, which has positive and negative peaks of a predetermined amplitude occurring alternately at the selected periodical time interval, takes the same level as the sampled level of the modulating wave. On the basis of the time interval, the PWM signal is produced.

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Kanasagou, Japan

Keijiro Sakai