A power conversion system comprises: a first power converter (1) for converting AC into DC; a second power converter (2) for converting the DC into the AC; a current detecting means (4) for detecting an output current of the second power converter (2); a ripple detecting means (5) for detecting the ripple component associated with conversion of the AC into the DC by the first power converter (1) from a ripple component contained in at least any one of the active power, inactive power, and apparent power of the second power converter (2); a voltage correcting means (6) for outputting the amount of correction to correct at least any one of the phase, frequency, and amplitude of a voltage to be outputted by the second power converter (2) on the basis of the ripple component obtained from the ripple detecting means (5); and a voltage control means (7) for outputting a voltage command to be issued by the second power converter (2) on the basis of the correction amount obtained from the voltage correcting means (6). The second converter (2) converts the DC into the AC on the basis of the voltage command obtained from the voltage control means (7).

Power conversion system

PURPOSE:To control to drive a motor with high stability without generating a beating phenomenon of a motor current by smoothing the terminal voltage of a filter capacitor. CONSTITUTION:A harmonic component detector 30 detects the high frequency component of twice of the frequency of a power source voltage. An adder 21 adds a value responsive to the harmonic component to a slip frequency fs. An adder 22 adds a motor frequency fr to the added value at power drive time, and subtracts the motor frequency fr therefrom at regenerative time, an inverter frequency signal finv obtained by this addition of subtraction is applied to a firing pulse generator 23 to control a commutation in response thereto. As a result, the harmonic component or the component of a frequency band near it is suppressed in the filter capacitor terminal voltage EFC.

Driving device for motor

PURPOSE:To aim at the promotion of small capacity in a spare gas storage system by separating fuel gas other than the specific load from a generator when city gas supply is stopped and pressure to an engine becomes less than the specified value, while supplying the engine with the fuel gas from a spare gas supply system. CONSTITUTION:A gas system transfer controller 22 closes a valve 6 and opens a valve 15 instead when city gas supply out of a feed pipe 7 is stopped and pressure P1 in a gas pipe 4 being detected by a pressure gauge 20 goes down to less than the specified value, and feeds an engine of a gas generator 1 with spare gas out of a spare gas storage tank 19 via a valve 18 and a pressure reducing valve 17, controlling the engine 2 by an engine controller 8 according to output of a generator 3. Simultaneously switches 11b-11n of power distribution systems 12b-12n excepting 12a are turned off via a switch control panel 13. And, when pressure P2 to be detected by a pressure gauge 21 goes down to less than the specified value, the engine 2 is stopped while a switch 11a is turned off. Thus, the promotion of small capacity in a spare gas storage system is contrivable.

Power generating system using city gas

A welding camera (1) is constructed with: a lens (11) for focusing incident light; an optical filter (12) that comprises a neutral density filter for reducing the amount of the incident light, an ultraviolet cut filter for cutting ultraviolet rays, and a green band-pass filter for transmitting green light; a CMOS imaging unit (13) that has a wide dynamic range function, and detects the light which has passed the optical filter (12); a video signal processing unit (14) that has an automatic gain control function and a digital signal processor, and outputs an image signal, which covers a range of a low-intensity dark part to high-intensity arc light, to a display unit on the basis of an electric signal that is input from the CMOS imaging unit (13).

Imaging device for welding

PURPOSE:To suppress the beating phenomenon of an output current by detecting an input DC voltage, and varying the frequency of a voltage type inverter proportionally thereto. CONSTITUTION:A rectifier 2 is connected to an AC power source 1, and a DC power is supplied through a capacitor 3 to a voltage type inverter 4. The AC motor 5 of a load is driven by the output of the inverter 4. In this case, a voltage detector 10 for detecting the DC input voltage of the inverter and a voltage controlled oscillator 20 for generating a pulse having a frequency proportional to an input voltage value are provided in a controller, and a control pulse is distributed to individual semiconductor switches in the inverter through a pulse distributor at the rear stage of the oscillator 20. Thus, an inverter angle frequency is varied proportionally to the DC input voltage of the inverter, thereby bringing voltage and time products in positive and negative polarity periods of the output voltage of the inverter and eliminating DC component in the output voltage of the inverter.

Method of controlling voltage type inverter

PURPOSE:To prevent the mutual interference of frequencies between the input and the output by providing a beat phenomenon detector when an AC generator is driven by a variable speed drive source and a load is connected through a stationary converter, thereby correcting a frequency command. CONSTITUTION:An AC generator 1 is driven by an engine or the like, and electric power is supplied through a stationary converter 2 which has a power reactor 3 and a power inverter 6 to a load 7. At this time, a beat phenomenon detector 10 is provided at the output side of the converter 2, a frequency command to a frequency converter 9 is corrected by the output, thereby slightly displacing the frequency command. Accordingly, frequency difference can be always produced between the input and the output of the converter 2, thereby reducing the size of the system without increasing the reactor 4 and the condenser 5 in the converter 2 and preventing the beat phenomenon which occurs when the frequencies of the input and output approach to each other.

Masahiko Iwata

Papers

Spindle drive generating system