The phase sequence table is used to control the phase sequence of the three-phase power supply. When the phase sequence is correct, the relays of the phase sequence table will pull in; if the phase sequence is incorrect, the relays of the phase sequence table will not pull in. There are A-phase, B-phase, and C-phase in the three-phase power supply. If the power is connected to the motor according to the ABC phase sequence, and the motor is forward rotation, then the motor is reversed according to the ACB phase sequence power supply. In order to prevent the motor from reversing, a phase sequence table is added to prevent the phase sequence of the incoming power supply from being reversed, causing the motor to reverse. The phase sequence table can detect the five failure phenomena of phase loss, reverse phase, three-phase voltage imbalance, overvoltage and undervoltage that occur in industrial electricity, and disconnect the electrical equipment in time to play the earliest phase sequence for protection The internal structure of the table is similar to a three-phase AC motor, with three-phase AC windings and a very light rotor, which can rotate under a small torque, and the working voltage range of the three-phase AC winding is very wide from tens of volts to 500 volts jobs. During the test, the phase sequence is determined according to the direction of rotation of the rotor. There are also resistance-capacitance phase-shifting circuits, so that different phase sequences have different signal lights to show the phase sequence.
1. How to use the phase sequence table
1 Wiring: Connect the three lead wires A (red, R), B (blue, S), C (black, T) of the phase sequence table to the A (R), B (S), C ( T) Three online.
2 Measurement: Press the measurement button in the upper left corner of the meter, the light is on, and the measurement starts. When the measurement button is released, the measurement is stopped.
3 Phase loss indication: The three red LEDs on the panel indicate the corresponding three-phase incoming calls respectively. When the measured source is out of phase, the corresponding LED is not bright.
4 Phase sequence indication: When the three-phase phase sequence of the measured source is correct, the green light corresponding to the positive phase sequence lights up, and when the three-phase phase sequence of the measured source is wrong, the red light corresponding to the reverse phase sequence lights up and beeps The alarm sounds.
Note 1: The positive phase sequence means that UA0, UB0, UC0 (or UAB, UBC, UCA) lags 120 degrees in sequence; the reverse phase sequence means that UA0, UB0, UC0 (or UAB, UBC, UCA) leads 120 degrees in sequence.
Note 2: To change the reverse phase sequence to the positive phase sequence, just exchange any two of the three lines A, B, and C. The measurement time is unlimited. Precautions for using phase sequence table
1. When using the phase sequence table, no other power supply or battery is needed for its power supply, but it can be directly powered by the power supply under test.
2. Most phase sequence tables have the function of indicating missing phases. In general, the panel of the phase sequence table has three light-emitting diodes A, B, and C, which correspond to three-phase calls. If there is a phase loss in the power supply under test, the corresponding diode will not emit light.
3. The insulated alligator clip of the phase sequence table can be used to clamp and detect insulated wires with a diameter between 2.4-30mm.
4. When using a phase sequence meter, if one of the three-phase input lines is connected to electricity, the meter will be charged, so we must cut off the power before opening the cabinet.
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