Kabushiki Kaisha Toshiba

Tokyo Shibaura Denki Kabushiki Kaisha

Akio Hirata

Suzuo Saito

Kazuto Kawakami

Tadao Mose

Kazuhiro Satoh

Kosaku Ichikawa

Yoshiaki Miyazawa

Teruo Nakagawa

Akihiko Kuroiwa

Kohsaku Ichikawa

Hidehiko Kikuchi

Michiro Yamazaki

Teruo Nakano

Yosio Naito

Tsugunori Kuga

A multiple inverter system of the present invention is disclosed. It includes a plurality of input transformers having secondary windings and a plurality of unit inverter cells connected in series at n stages to compose respective phases and supply the electric power to a multiple phase load in combination with the input transformers. The input transformers have 3n sets of three-phase windings at the secondary side and the secondary windings of the transformers, which are out-of-phase at each phase, are connected to unit inverter cells of each phase at the n-th stages. Further, the present invention is provided with a bypass switch control to melt a fuse that is applicable to a unit inverter given with a circuit closing command by giving this circuit closing command to a bypass switch corresponding to applicable unit inverters in response to an operation abnormality detector and a DC abnormality detector.

Multiple inverter system

A power converter having at least a pair of voltage drive switching elements, which comprises a gate control circuit, the gate control circuit comprising a detecting section for detecting at least one of a set of device parameters and a set of electric parameters of the voltage drive switching elements, a monitoring section for monitoring at least one of states of turn-on and turn-off of the voltage drive switching elements based on the at least one of a set of device parameters and a set of electric parameters of the voltage drive switching elements detected by the detecting section, and a control section for controlling a gate of the voltage drive switching elements based on a monitoring result of the monitoring section.

Power converter with voltage drive switching device monitored by device

A power inverting method and system for connecting a plurality of AC power supplies to a common bus line in parallel wherein the AC power supplies are independently controlled so that power supplies with different rating characteristics can be coupled to the common bus line without adverse effects such as the existence of cross currents flowing between the different power supplies. In each AC power supply there is provided a system parameter calculating unit for calculating optimum load current, system impedance and output voltage parameters of the power supply which are then output to a reference data producing unit which generates appropriate feedback voltage and phase signals for output to a voltage controller and a phase synchronization controller, respectively. The voltage controller and phase synchronization controller output feedback signals to a power inverter which varies the power supply output. Using such feedback control in each of the plurality of power supply units enables a constant current to be output to a load on the system and eliminates the possibility of cross currents between the various power supply units.

Parallel connection of different types of AC power supplies of differing

A power supply is energized by an external power source and a battery, and supplies electric power to a load. The power supply includes a battery voltage detector and a current detector for detecting a discharge current from the battery. The remaining capacity of the battery is detected in accordance with a change in the battery voltage when the external power source is free of power failure. The battery voltage change is defined as the difference between an initial voltage of the battery and an active voltage of the battery obtained when the battery is discharged by the detected discharge current for a predetermined period of time.

Uninterruptible power supply diagnosing remaining battery capacity

A turbine helper drive apparatus includes a turbine for driving a load, a motor coupled to the turbine, and a power converter for controlling an output from the motor based on a predetermined power reference. The power converter controls the motor so that the motor performs either a motoring operation, wherein the motor drives the load together with the turbine, or a regenerating operation, wherein the motor serves as a load for the turbine to generate an electric power.

Turbine helper drive apparatus

A helper drive apparatus for a turbine drive system in which a load is mainly driven by a turbine and a helper motor is used for assisting the drive for the load, comprising: a turbine control circuit, coupled to the turbine, for controlling output power of the turbine in accordance with a turbine power reference signal; a motor control circuit, coupled to the helper motor, for controlling output power of the helper motor in accordance with a motor power reference signal; a speed control means, coupled to the turbine, for detecting a difference between a given speed reference signal and a speed signal indicating an operation speed of the turbine, and providing a master power reference signal representing the difference; and a power sharing ratio control circuit, coupled to the speed control circuit, turbine control circuit, and motor control circuit, and being responsive to a given power sharing instruction signal, for sharing the master power reference signal to the turbine power reference signal and the motor power reference signal such that a ratio between the turbine power reference signal and the motor power reference signal depends on a value of the given power sharing instruction signal.

Helper drive apparatus for turbine drive system

A self-extinguishing element such as a gate turn-off thyristor (GTO) is used for each arm of the inverter. A capacitive load is connected to the output terminal of the inverter. In a region where the output frequency of the inverter is low, the self-extinguishing element is forcibly commutated. In a high-frequency region, where the output frequency of the inverter is higher than that in the low-frequency region, the capacitive load causes the self-extinguishing element to be load-commutated.

AC motor control method and its control apparatus

A turbine helper drive apparatus has an induction motor coupled to a turbine, and a power converter for power-controlling the motor. Part of the load of the turbine is shared by the motor in accordance with preset power for power control, so that auxiliary drive to compensate for the insufficient capacity of the turbine is performed and cheaper, late-night electric power is effectively utilized.

A load-commutated inverter for operating a synchronous motor having two sets of 3-phase windings. The difference of phase angles between the two sets of the 3-phase windings is 30 degrees. The load-commutated inverter is provided with two sets of inverters and a control circuit. Each of the inverters, is formed of thyristors. The inverters are coupled respectively to the 3-phase windings of the motor. The commutation of each of the thyristors is controlled in accordance with a given advanced control angle. The control circuit is coupled to the inverters and is responsive to a commutation overlapping angle of currents (e.g., IU1, IV1 in FIG. 4A) supplied from the inverters to the 3-phase windings of the motor. The control circuit adjusts the given advanced control angle so as to retain a relation:

Load-commutated inverter for operating synchronous motor

A control system for an AC motor to be driven by an inverter, wherein a control lead angle .beta. of the AC motor drive current is controlled based on the detection of an actual overlapped angle, a set overlapped angle, a detected motor speed, a detected magnitude of the acceleration-deceleration rate of motor speed, a detected amount of current from a power source and/or a detected magnitude of the change rate in the current from the power source.

Control system for an AC motor

Apparatus and method for controlling a synchronous motor driving a square-law torque load at variable speeds by employing a frequency changer. The armature voltage Va may be controlled so that the ratio Va/N at motor speeds above a predetermined value is greater than Va(100)/N(100), where N(100) is the rated speed of the motor and Va(100) is the armature voltage at that speed. Below a predetermined speed, the armature voltage may be controlled so that the ratio Va/N is less than Va(100)/N(100).

Synchronous motor control

A synchronous motor is driven by a plurality of inverting circuits. The inverting circuits are controlled by signals from a position detecting circuit coupled to the shaft of the synchronous motor so as to produce output current signals from the inverting circuits which are shifted by a certain angle from each other.

Controlling device for a brushless motor

A power converting device including at least one power converting element, and a protection circuit monitoring the switching characteristics of the power converting element and for protecting the power converting element during switching thereof, including a first circuit coupled to detect a reverse voltage applied to the power converting element, a second circuit coupled to the first circuit for receiving the detected reverse voltage and for integrating the detected reverse voltage to produce a reverse voltage/time integral signal, and a third circuit coupled to receive the reverse voltage/time integral signal for producing a decision signal only when the amplitude of the reverse voltage/time integral signal exceeds a first prescribed value, the decision signal indicates that the power converting element is extinguished.

Power converting device and a protection device for the same

In a method and apparatus for controlling a speed of an AC motor energized by a source of alternating current through a frequency converter, a limiter responsive to input voltage and input current is provided for decreasing a primary frequency at a rate faster than a rate of decrease in a number of revolutions of the motor when the source is interrupted for a short interval and for accelerating the motor with a primary current thereof limited to a predetermined value while maintaining the primary frequency and the primary current in a predetermined relation.

Method and apparatus for controlling alternating current motors

A frequency converter applies a variable voltage with a variable frequency to an AC motor coupled with a load. At least one frequency region is set up for the variable frequency. The ratio of a percentage input voltage expressed in terms of a percentage of the rated input voltage of the AC motor, to a corresponding percentage input frequency expressed in terms of a percentage of the rated input frequency of the AC motor, is set less than 1 within the frequency region thus set. Also an apparatus for the AC motor control provided.

Growing community of inventors

Tokyo, Japan

Akio Hirata