| 摘要 |
PURPOSE:To provide an alternating-current detector that can eliminate the delay of detection by adding a first phase detection current to a weight factor, related with a detection delay, multiplied by a second phase detection current advanced by 90 degrees from the first phase detection current. CONSTITUTION:An alternating current from a three-phase AC power supply 1 is converted to a direct current through a converter 4 to supply power to a load of an apparatus 5. In a subtractor 101, a U-phase line current (iu) detected by a current detector 2 and a V-phase line current (iv) detected by a current detector 3, both in negative polarity, are added to each other to obtain a W-phase line current (iw). The line currents (iu and iw) are each entered in a multiplier 104 or 105, in which a counting voltage is added with a counter 102 or 103, and the output from multipliers 104 and 105 are added to each other by an adder 106 to obtain an output (1ua). As an example, assuming that a delay (Td) is caused by a detection time of the line current (iu), a filter, an insulating amplifier, and the like. If the line current (Iua), which is advanced by an angel (thetad) that is in accordance with the delay (Td), is detected instead of the current (Iu), the alternating current can be detected equivalently, because the angle (thetad) and the delay (Td) are canceled out. |
