| 摘要 |
PURPOSE: To determine correct phase sequence easily by an arrangement wherein an impedance connects two resistors of equivalent system and one capacitor in Y and the difference of output from analog comparison networks connected, in row, with one resistor is monitored. CONSTITUTION: Resistors R1, R2 of identical resistance and a capacitor C1 having an equivalent impedance are connected, in Y, with lines A, C and B. A comparator network 12 is connected with the line A through the resistor R1. A comparator 1 has an inverted input receiving the fixed reference voltage V- of a Zener diode Z1 and an non-inverted input receiving a voltage V+ obtained by dividing Vcc by resistors R4, R5. In case of correct phase sequence as shown on the figure, the voltage V+ is lower than the voltage V- and a transistor on the output side of the comparator 1 is turned on. Consequently, a current flows through a resistor R7 to turn off a transistor Tr Q1 and an opto-isolator 14 does not emit light. In case of erroneous phase sequence, a current flows through the resistors R7, R8 to turn on the transistor Tr Q1 and the opto-isolator 14 emits light. According to the arrangement, phase sequence can be determined easily. |
