Hitachi, Ltd.

Kenji Nandoh

Motonobu Hattori

Akira Ishibashi

Satoshi Ibori

Nobuyoshi Mutoh

Akiteru Ueda

Keijiro Sakai

Hideyuki Shimonabe

Hiroshi Fujii

Tsunehiro Endo

Seiji Ishida

Yasuo Matsuda

Toshio Suzuki

Nobuyoshi Muto

Tadao Shimotsu

Yuuzi Yamasawa

Yasuharu Tamuro

Shigeyuki Baba

Ikuo Okajima

Takatsugu Kanbara

Shigeru Murasaki

Hiroyuki Benya

Hiromi Ishida

An inverter apparatus includes a basic control section including a main circuit which includes an inverter, and a control unit which controls the main circuit. The inverter apparatus also includes an I/O block which is connected to the basic control section, and is selected from a plurality of different types of I/O blocks. The I/O block includes an input/output interface. The input/output interface includes a signal connection terminal which transmits an input/output signal to/from the control unit. Operation management specifications of the main circuit are fixed independently of operation management specifications of the input/output interface. Operation specifications of the inverter apparatus change depending on the operation management specifications of the input/output interface, and are determined by the type of the I/O block which is connected to the basic control section, such that connecting the different types of I/O blocks to the basic control section causes the inverter apparatus to have different operation specifications.

Inverter apparatus having operation specifications determined by type of

This specification discloses an overcurrent protective circuit for detecting an overcurrent flowing through an electrostatic self-turn-off device and suppressing the overcurrent. The overcurrent protective circuit according to the present invention comprises a power source for supplying a driving voltage to the electrostatic self-turn-off device to turn on the device, a switching circuit for performing on-off control of the driving voltage to provide a driving signal to the self-turn-off device, and a circuit for detecting the voltage of the driving control terminal and holding the potential of the driving control terminal below the driving voltage in response to the detected voltage reaching a predetermined value.

Overcurrent protective circuit for electrostatic self-turn-off devices

A method and apparatus are disclosed for controlling a pulse width modulated (PWM) inverter controlled for ignition by a (PWM) pulse produced with a carrier wave and a modulation wave. The method comprises sampling an amplitude of the modulation wave at a cycle rate related to the frequency of the carrier wave. The modulation wave and the carrier wave are synchronized when the sample modulation wave amplitude has a peak value greater than an amplitude of the carrier wave. The modulation wave and the carrier wave are asynchronized when the sampled modulation wave has a peak value less than the amplitude of the carrier wave.

Method and apparatus for selectively controlling an operation mode of a

A control system for controlling a PWM inverter so that the inverter drives an induction motor at a variable voltage and a variable frequency while keeping constant a ratio of the output voltage of the inverter to the output frequency thereof, is disclosed which includes current component detecting means for detecting an effective current corresponding to a load, from the input current of the induction motor, frequency setting means for setting the output frequency of the PWM inverter, flux setting means for setting the amount of magnetic flux generated in the induction motor, correcting-frequency calculating means for calculating a frequency correcting quantity proportional to the effective current, and correcting-flux calculating means for calculating a flux correcting quantity proportional to the effective current. In a case where the detected effective current is judged to be less than a predetermined value, the frequency correcting quantity is added to the set output frequency to obtain an output frequency command, and the sum of the flux correcting quantity and the set amount of magnetic flux is multiplied by the value of the output frequency command to obtain an output voltage command, for the purpose of controlling the operation of the PWM inverter on the basis of the output frequency command and the output voltage command.

Control system for PWM inverter

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 inverter for converting DC power to AC power, an oscillation control circuit for stepwise generating a command value concerning the conversion condition of the inverter, and an operation controller which, when the command value from the oscillation control circuit changes, controls the oscillation control circuit to repetitively generate alternate new and old or present command values before and after change of the command value. Particularly, this invention provides an inverter capable of continuing smooth operation even when the control system has a limited resolution.

PWM inverter apparatus with digital control

A power inverter including a converter unit for rectifying AC power into DC power, an inverter for inverting the DC power into AC power for driving a load apparatus, and a protection apparatus for protecting the load apparatus from being overloaded. The load protecting apparatus comprises current detecting means for detecting a current supplied to the inverter unit from the converter unit, a memory for storing a thermally limited operation time characteristic determined in consideration of cooling effect proper to the load apparatus, and an abnormality detecting circuit for producing an abnormality signal to stop the operation of the inverter unit when an accumulated value calculated on the basis of the current value detected by the current detector at a predetermined sampling interval exceeds the characteristic value previously stored in the memory. The load apparatus can be positively protected from overload notwithstanding variations in the output voltage and the output frequency of the power inverter.

Power inverter with overload protection apparatus

A pulse width modulation inverter is controlled by the use of the fundamental wave voltage E.sub.1 of the inverter output as a feedback quantity, the fundamental wave voltage E.sub.1 being obtained as the product of a function g(K.sub.H) which is determined by the amplitude ratio K.sub.H of a carrier wave and a modulated wave, and a d.c. voltage E.sub.D input of the inverter.

Method of controlling the output voltage of a pulse width modulation

A method and apparatus for controlling an induction motor, in which an AC power source is connected to the induction motor through a switch and a frequency converter, and the motor speed is controlled by controlling the output frequency and output voltage of the frequency converter. In the starting operation, the induction motor in a free-running state is supplied with an initial voltage in a given frequency which is expected to make the absolute value of the motor current minimum or near minimum, and then the supply voltage is increased gradually from the initial voltage with its frequency being retained at the given voltage. When the output frequency of the frequency converter reaches a predetermined value, the output frequency and voltage thereof are increased gradually with the ratio therebetween being maintained at a given value.

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Matsudo, Japan

Kenji Nandoh