| 摘要 |
PURPOSE:To decide whether there is an abnormal condition irrespective of sizes of system current or voltage by deriving a difference between the maximum and minimum of three phase of the system current of voltage detected by an analogue input section as the ratio to the maximum. CONSTITUTION:An absolute value operation section 11 derives each absolute value from sample values of detected current IR, IS, IT to be taken-in from an analogue input section. From the maximum(MAX) and minimum(MIN) of the absolute value, a subtraction section 13 derives the difference DIF, a multiplier section 14 derives a value (A) multiplying by a ratio coefficient (epsilon3), a size comparison section 15 derives a value (B) comparing (A) with the sizes of the difference DIF, and a size comparison section 16 compares MAX with the sixes (C) of a setting (epsilon4). A condition section 17 outputs a comparison result of the (B) as the result to decide whether or no there is an abnormal condition, subject to the (C). The decision result is such that the difference between the maximum and minimum of the current value of each phase is more than epsilon3 percent, that is, when it is given by a formula shown in the figure, it is decided that the analogue input section is in an abnormal condition. |
