First, the fault is judged based on the fault indicator.When the electric actuator valve is energized, its power indicator does not light, and the 4-20 mA control signal does not work.Since the power indicator does not light, you should first check if the fuse is open.If the fuse is open, replace the fuse of the same specification. Then power on debugging.If the fuse is intact, it can be judged that the fault may occur in the power supply section of the servo board, and then the power indicator light is checked.Use a multimeter to detect that the indicator light is faulty. Replace the indicator of the same specification.The conclusion is that the power indicator failure will cause the servo board to not work.The given open signal is normal. When the signal is off, the closing indicator light is off and the actuator is not active. Fault judgment: when the open signal is given, the valve opening indicator lights, indicating that the given line and the feedback line are normal. Instead, when the off signal is given, the off indicator does not light. Explain that the thyristor part is faulty.First check the off indicator light, use the multimeter to detect the off indicator light, and replace the off indicator with the same specifications. Therefore, the thyristor does not operate when the open and closed indicator lights are not lit.
Second, the fault phenomenon, as long as a power supply, the protection switch immediately trips.Use a multimeter to detect the motor windings on the electric actuator valve and find that the motor winding is short-circuited and its resistance tends to zero.Then check the resistance of the two ends of the brake, its resistance tends to infinity, indicating that the brake is broken, the normal should be about 1.5kΩ. With the replacement of the new motor and brake, and the fuse of the servo plate.Re-commissioning resumes normal work. The fault should be that the brake is broken, the motor is locked, and no replacement is found on the site, so that the motor is blocked and forwarded for a long time and burned.
The three factors affecting the steering of the electric actuator valve, the winding of the motor itself, the current limiting resistor, and the phase shifting capacitor. There is no other possibility besides these. If the direction of action of the electric actuator valve is not controlled by the input signal.Check that there is no abnormality between the current limiting resistor and the phase shifting capacitor. Check the resistance of the motor winding with a multimeter and find that the resistance value is erratic and change. Replace the motor fault to eliminate.Then there is the fault phenomenon caused by the resistor and capacitor. If the electric actuator valve is energized, given a signal of an action, for example, to 50%, the actuator action is fully open to the end and then open to the given position 50%.Use a multimeter to check that the motor windings are normal, and then measure the resistance on both sides of the capacitor to find one of the open circuits. After replacement, the electric actuator valve works normally.