Abstract: An inverter output current detection device is provided which can calculate an output current of an inverter easily by using a low-performance calculating device without lowering a calculation accuracy. A current ic? equivalent to a capacitor current ic is digitally calculated according to a predetermined expression. This expression is ic?=V×?0×C×[cos Wavedata]×K, where V is an effective value or average value of an output voltage vo, C is a capacitance of a capacitor C, ?0 is an angular frequency of the output voltage, and K is a value obtained by multiplying a detection ratio for detecting the output voltage vo, a conversion ratio for converting an analog value into a digital value, and a conversion ratio for converting the effective value or average value V into a maximum value.

Abstract: An inverter output current detection device is provided which can calculate an output current of an inverter easily by using a low-performance calculating device without lowering a calculation accuracy. A current ic? equivalent to a capacitor current ic is digitally calculated according to a predetermined expression. This expression is ic?=V×?0×C×[cos Wavedata]×K, where V is an effective value or average value of an output voltage vo, C is a capacitance of a capacitor C, ?0 is an angular frequency of the output voltage, and K is a value obtained by multiplying a detection ratio for detecting the output voltage vo, a conversion ratio for converting an analog value into a digital value, and a conversion ratio for converting the effective value or average value V into a maximum value.

Abstract: An electric power conversion apparatus is provided which can protect the electric power conversion circuit against an overcurrent even when the interrupting circuit for preventing an inflow of an overcurrent into the input side caused by phase deviations between an input voltage and an output voltage uses switching means with a slow responsiveness. The switching means used in the interrupting circuit 2 have a slower response speed than those of semiconductor switching elements. The overcurrent detection circuit 3 checks whether the input current is an overcurrent. For as long as an overcurrent is detected by the overcurrent detection circuit 3, the command input blocking circuit 4 blocks the instantaneous current control signal and the instantaneous voltage control signals from being fed into the drive signal generation circuit 5. As the duration of overcurrent increases, the interrupting circuit 2 is activated to interrupt the current inflow.

Abstract: A controlled rectifier equipment with sinusoidal waveform supply current is provided, in which equipment an inexpensive AC current transformer can be used as an AC current detector. The AC current transformer is used as an AC current detector. A DC component eliminating circuit including a low pass filter which cuts off the frequency component of commercial AC power supply is arranged on the line between an current controller in a current control system and a modulation circuit in the conduction control signal generating circuit. The circuit is formed so that a DC offset component which is generated in a controlled rectifier equipment may be eliminated.

Abstract: A parallel operation-type uninterruptible power system capable of preventing one of uninterruptible power systems from being extremely increased in load sharing ratio without having to operate each uninterruptible power system while watching operation of the remaining uninterruptible power systems. The uninterruptible power systems each are constituted by an inverter circuit and an inverter circuit control device. The inverter circuit control device includes a PWM control signal generating means. The PWM control signal generating means generates a PWM control signal so as to gradually reduce an output voltage of the inverter circuit as supply active power increases and until a judging means judges that the supply active power has reached a predetermined level and so as to reduce the output voltage at a reduction ratio increased as compared with before to keep it from falling into an overload condition when the judging means judges that the supply active power has reached the predetermined level.

Abstract: A controlled rectifier equipment with sinusoidal waveform supply current is provided, in which equipment an inexpensive AC current transformer can be used as an AC current detector. The AC current transformer is used as an AC current detector. A DC component eliminating circuit including a low pass filter which cuts off the frequency component of commercial AC power supply is arranged on the line between an current controller in a current control system and a modulation circuit in the conduction control signal generating circuit. The circuit is formed so that a DC offset component which is generated in a controlled rectifier equipment may be eliminated.

Abstract: An electric power conversion apparatus is provided which can protect the electric power conversion circuit against an overcurrent even when the interrupting circuit for preventing an inflow of an overcurrent into the input side caused by phase deviations between an input voltage and an output voltage uses switching means with a slow responsiveness. The switching means used in the interrupting circuit 2 have a slower response speed than those of semiconductor switching elements. The overcurrent detection circuit 3 checks whether the input current is an overcurrent. For as long as an overcurrent is detected by the overcurrent detection circuit 3, the command input blocking circuit 4 blocks the instantaneous current control signal and the instantaneous voltage control signals from being fed into the drive signal generation circuit 5. As the duration of overcurrent increases, the interrupting circuit 2 is activated to interrupt the current inflow.

Abstract: A parallel operation-type uninterruptible power system capable of preventing one of uninterruptible power systems from being extremely increased in load sharing ratio without having to operate each uninterruptible power system while watching operation of the remaining uninterruptible power systems. The uninterruptible power systems each are constituted by an inverter circuit and an inverter circuit control device. The inverter circuit control device includes a PWM control signal generating means. The PWM control signal generating means generates a PWM control signal so as to gradually reduce an output voltage of the inverter circuit as supply active power increases and until a judging means judges that the supply active power has reached a predetermined level and so as to reduce the output voltage at a reduction ratio increased as compared with before to keep it from falling into an overload condition when the judging means judges that the supply active power has reached the predetermined level.