| 摘要 |
PURPOSE:To detect a phase difference with high accuracy, by sampling two AC inputs from the same electric power source system, and using sampling values before and after zero-crossing of the AC inputs and a phase difference between each sampling. CONSTITUTION:Two AC inputs inputted from the same electric power source system are sampled by a prescribed sampling frequency, and are converted to digital values. A negative sampling value X0 and a positive sampling value X1 in case when the input A1 is changed to positive from negative for to its polarity are derived, and in the same way, a negative sampling value X20 and a positive sampling value X21 of the input A2 are derived. Subsequently, a sampling number N0 extending from the sampling value X1 of the input A1 to the negative sampling value X20 of the input A2 is counted. Subsequently, a phase difference theta between each sampling in the actual power supply frequency is derived, phase difference alpha, beta are derived by use of the sampling values X0, X1, X20 and X21 and the phase difference theta; the phase difference between two inputs is detected. |
