1. Burned Motor of RM Type Actuator
For standard NORM-type actuators, motor burnout is generally caused by incorrect wiring and improper parameter setting.The correct circuit configuration shall provide the motor with five types of protection: limit switch, torque switch, thermal protection switch, thermal relay and air circuit breaker inside the MCC power distribution cabinet.
Users often fail to connect the thermal protection switch and set the torque switch to the maximum value. When the limit switch is damaged or the actuator stops at the intermediate position, the motor is likely to burn out.It is also common for users to equip oversized air circuit breakers or set excessive current values for thermal relays. Refer to the technical manual to verify and correct the setting values of air breakers and thermal relays.
For SG type actuators, the limit switches and END-STOP mechanical limiters must be precisely adjusted; otherwise motor burnout will easily occur.The adjustment method for SG differs from SA. A proper margin shall be reserved for limit switch setting (retard 3-4 circles).
2. Local Control Head Fails to Operate
First check whether the fault indicator light is on.
(1) If the fault light is on
Check for phase loss.
Check for over-torque fault: Unplug the X1 connector on the logic board (count from the left as terminal 1). Measure continuity between terminal 5 and 6 for opening torque, and between terminal 11 and 12 for closing torque. Discontinuity indicates over-torque protection activation, which needs to be reset.
Check motor overheating / faulty thermal protection switch: Unplug the X1 connector on the logic board. Measure continuity between terminal 1 and 2. Discontinuity means motor overheating or thermal protection switch failure.
The power board may misjudge phase loss; replace the power board for verification.
The logic board may be faulty; replace the logic board for verification.
(2) If the fault light is off
Confirm main power supply is switched on.
Check whether the four fuses are blown.
Verify that both open limit switch and close limit switch reach their full stroke positions simultaneously.
Inspect 24VDC, 24VAC on the power board, and power supply on the white connector for the logic board; replace the power board for verification.
Replace the faulty logic board for testing.
Check loose wiring on contactors or thyristors; measure coil resistance and contact closing status of contactors; test resistance of thyristors; replace faulty components for verification.
Replace faulty button board or selector switch for verification.
3. Local Operation Normal, Remote Control Fails
This fault is directly related to the feedback board and positioning board. Observe whether the red indicator V10 is lit.
(1) If V10 is lit
Check if the command signal polarity is reversed.
Check if the command signal is lower than 4mA.
Check if the feedback signal is lower than 4mA.
Apply simulated signal via a handheld signal generator for testing. If the red light goes out and remote control resumes normal operation, install a signal isolator as required by the owner.
The V10 red light may also turn on if the input signal is voltage source instead of constant current source.
Replace the faulty positioning board for verification.
(2) If V10 is not lit
Replace the positioning board for troubleshooting.
4. Modulating Type Actuator No Position Feedback Signal
(Measure from test terminals on the feedback board)
No feedback signal if external circuit terminals 23 and 24 are open-circuited.
Measure 27VDC between terminal 1 and 2; no voltage indicates possible positioning board damage.
If 27VDC exists between 1 and 2 but no current output at 3 and 4, the feedback board is likely faulty.
Disconnect terminals 5, 6, 7 from the feedback board. Resistance between 5 and 7 should be 5kΩ; resistance between 5&6 or 6&7 shall change uniformly when the actuator travels from fully closed to fully open, which confirms the potentiometer is intact.
Open-circuited potentiometer resistance usually causes abnormally high feedback signal.
If feedback signal exists but changes slightly from full close to full open, replace feedback board and positioning board for testing.
5. Oscillation Fault of Modulating Actuator
Check for fluctuation of command signal.
Turn potentiometer P9 clockwise to increase dead zone.
Install a signal isolator.
Check if the actuator running speed is excessively fast.
Replace the positioning board.
6. Failed Adjustment of Position Feedback Signal (Modulating Type)
(1) Feedback signal exceeds 20mA and remains unchanged while the actuator is still running
Shorten the full stroke travel.
Replace the reduction gear set.
(2) Feedback signal can only be adjusted within 4mA to more than ten mA
Check whether the rotation angle of the GF swing arm from fully open to fully closed is greater than 75°. Adjust the connecting rod length to increase the swing angle of the GF arm.
Increase the full stroke travel.
Replace the reduction gear set.
Modify the range of DCS signal: e.g. set 0% corresponding to 4mA and 100% corresponding to 16mA.
Note: Calculation formula for reduction gear ratioFull stroke time × Rated speed on NORM nameplate × 1.55
7. Control Head Cannot Be Powered On
Inspect cable insulation and rated capacity of the air circuit breaker.
Replace the suspected faulty power board for verification.
Replace the suspected faulty thyristor for verification.
8. Control Head Powers On, Air Breaker Trips Immediately After Operation
Undersized rated capacity of air circuit breaker.
Replace faulty logic board.
Short-circuited contactor coil; replace contactor.
Motor short circuit; replace motor.
Damaged thyristor; replace thyristor.
9. Motor Burnout with Control Head Equipped
Sticky miniature relay on the button board.
Sticky contactor contacts.
Damaged thyristor.
Motor inherent failure.
Phase loss burnout caused by loose internal wiring.
10. Installation of Duplex Limit Switch
Do not pull out the counter when installing a duplex switch.The wire marked with number 2 of the duplex switch shall be connected between terminal 1–16; the unmarked wire shall be connected between terminal 25–40.
11. Actuator Shaft Breakage / Manual-Electric Switching Failure
Shaft breakage is mostly caused by excessive operating speed, and also related to frequent modulating operation, excessive valve friction, over-high torque setting and improper model selection.
Manual-electric switching failure is usually caused by operators forcing the red switching handle without rotating the handwheel, resulting in breakage of the pulling rod. It may also be caused by the baffle falling off at the motor connection.
