1.RM Type Actuator: Motor BurnoutFor basic NORM type actuators, motor burnout is usually caused by incorrect wiring or incorrect settings. The correct wiring shall provide the motor with five types of protection:
limit switches
torque switches
thermal protection switch
thermal relay in the MCC cabinet
circuit breaker
Users often leave the thermal protection switch unconnected and set the torque switch to maximum. If the limit switch fails or the actuator jams at an intermediate position, the motor may burn out.Users often install an oversized circuit breaker or set an excessively high current for the thermal relay. Refer to the manual for proper setting values of circuit breakers and thermal relays.
For SG type actuators, the limit switches and END‑STOP mechanical stops must be properly adjusted; otherwise, motor burnout is likely.SG adjustment differs from SA. Leave extra margin when setting limit switches (allow 3–4 turns back).
2.Control Head: No Local Operation
First check if the fault indicator is lit.
(1) If lit:
Check for phase loss.
Check for overload torque:Disconnect connector X1 on the logic board (pin 1 from left).Check if pins 5–6 (OPEN torque) are conducting.Check if pins 11–12 (CLOSE torque) are conducting.Non-conduction means torque tripped; reset required.
Check for motor overheating (thermal protection switch fault):Disconnect X1, check if pins 1–2 are conducting.Non-conduction indicates motor overheating or faulty thermal switch.
Check if the power board incorrectly detects phase loss; replace for verification.
Logic board may be defective; replace for verification.
(2) If not lit:
Check if power is applied.
Check if the four fuses are blown.
Check if OPEN and CLOSE limit switches are both activated simultaneously.
Check 24VDC and 24VAC on the power board, and power supply on the white connector to the logic board. Replace power board for verification.
Logic board defective; replace for verification.
Check for loose wiring on contactors or thyristors.Check contactor coil resistance and contact closure.Check thyristor resistance. Replace for verification.
Pushbutton board or selector switch defective; replace pushbutton board for verification.
3.Local Operation OK, Remote Operation FailedThis fault is related only to the feedback board and positioning board.Check if the V10 red LED is lit.
(1) If lit:
Check if the command signal polarity is reversed.
Check if command signal is below 4 mA.
Check if feedback signal is below 4 mA.
Verify using a handheld signal source. If the red LED turns off and remote control works, ask the owner to install a signal isolator.
V10 may also light up if the input signal is a constant-voltage source instead of a constant-current source.
Positioning board may be defective; replace for verification.
(2) If not lit:
Replace positioning board for verification.
4.Modulating Type: No Position Feedback Signal (measured at test pins on feedback board)
No feedback if external circuit (terminals 23, 24) is open.
Check for 27VDC at pins 1–2. If absent, the positioning board may be faulty.
If 27VDC exists at pins 1–2 but no current at 3–4, the feedback board is likely defective.
Disconnect wires 5, 6, 7 from the feedback board.Measure resistance between 5–7: should be approx. 5 kΩ.Resistance between 5–6 or 6–7 should change smoothly as the actuator moves from CLOSE to OPEN.This confirms the potentiometer is good.
An open potentiometer usually results in an excessively high feedback signal.
If feedback exists but changes very little from CLOSE to OPEN, replace feedback board and positioning board for verification.
5.Modulating Type: Hunting / Oscillation
Check if the command signal fluctuates.
Turn P9 clockwise to increase dead band.
Install a signal isolator.
Check if the actuator running speed is too high.
Replace positioning board.
6.Modulating Type: Cannot Set Proper Position Feedback Signal
(1) Feedback already exceeds 20 mA and stops changing while actuator is still running:
Reduce the full-stroke distance.
Replace the reduction gear.
(2) Feedback can only be adjusted from 4 mA to around ten mA:
Check if the rotation angle of the GF arm from FULL OPEN to FULL CLOSE is greater than 75°.Adjust the pull-rod length to increase the GF arm angle.
Increase the full-stroke distance.
Replace the reduction gear.
Modify the DCS signal range, e.g., set 0% = 4 mA, 100% = 16 mA.
Note: Reduction gear ratio formula:Full stroke time × motor speed on NORM nameplate × 1.55
7.Control Head: Cannot Power On
Check cable insulation and circuit breaker rating.
Power board may be defective; replace for verification.
Thyristors may be faulty; replace for verification.
8.Control Head Powers On, But Trips Immediately When Operating Pushbuttons
Circuit breaker rating too small.
Logic board defective; replace for verification.
Contactor coil short-circuited; replace for verification.
Motor short-circuited; replace for verification.
Thyristors faulty; replace for verification.
9.Motor Burnout with Control Head Installed
Small relay on pushbutton board welded closed.
Contactor welded closed.
Thyristor failure.
Motor internal fault.
Phase loss due to loose internal wiring causes burnout.
10.Installing Dual SwitchesDo not remove the counter when installing dual switches.
Wires marked “2” connect to terminals 1–16.
Unmarked wires connect to terminals 25–40.
11.Actuator Shaft Breakage or Hand/Auto Switching FailureShaft breakage is mostly caused by excessively high speed, and also related to:
frequent modulation
tight valve operation
excessive torque setting
improper selection
Hand/auto switching failure is usually caused by:
Construction personnel forcing the red lever without turning the handwheel, breaking the pulling rod.
Falling-off of the baffle at the motor connection.
