| 摘要 |
PURPOSE:To detect the effective value accurately and protect an inverter properly by composing an inverter output current effective value and a load current effective value so that the larger value between the two may remain, and operating overload protection according to this composed effective value. CONSTITUTION:An inverter output current effective value and a load current effective value are detected, respectively, in a first effective value circuit 21 and a second effective value circuit 22, separately, and are output to an OR circuit 6. In the OR circuit 6, those are composed so that the larger value between the inverter output current effective value and the load current effective value may be left, and this is output to a overload protective circuit 13. If a specified time passes in the condition that this composed effective value has fairly exceeded the overload withstanding quantity of an uninterruptive power unit, the overload protective circuit 13 operates, and performs such current limiting operation as to throttle the output voltage of an inverter 1 or stops the operation of the inverter 1. |
