PS Series

I. Indicator Faults

Fault SymptomAfter powering the actuator, the power indicator does not light up, there is no feedback from the servo board, and the actuator does not respond to input signals.

Fault Diagnosis and TroubleshootingSince the power indicator is off, first check whether the fuse is open-circuited. The fuse is found intact. Based on the overall fault symptoms, the fault is inferred to be in the power supply section of the servo board. The power indicator is then checked; multimeter measurement shows the indicator is open-circuited. The fault is eliminated after replacing the indicator.

ConclusionAn open-circuited power indicator can cause the entire servo board to stop working.

Fault Symptom (Found During Commissioning)After powering the actuator, it operates normally on the OPEN command but does not actuate on the CLOSE command.

Fault Diagnosis and TroubleshootingFirst carefully inspect the feedback circuit and confirm the feedback signal is normal. The OPEN indicator lights up when an OPEN signal is applied, indicating normal OPEN operation. The CLOSE indicator does not light up when a CLOSE signal is applied, indicating a fault in the CLOSE thyristor circuit. The CLOSE indicator is checked and found open-circuited via multimeter. The fault is resolved after replacement.

ConclusionWhen the OPEN or CLOSE indicator is off (open-circuited), the thyristor will not actuate.

II. Resistor and Capacitor Faults

Fault SymptomAfter powering the PSL210 actuator, when a signal (e.g. 75%) is applied, the actuator runs fully open and then returns to the specified position (75%).

Fault Diagnosis and TroubleshootingBased on the above symptoms, first determine whether the fault is in the servo board or the actuator itself. Remove the servo board and connect power directly to terminals X5/1 and X5/4; the actuator should move toward CLOSE. Connect power to X5/1 and X5/2; the actuator should move toward OPEN. Abnormal operation indicates a fault in the actuator.Motor windings measure normal with a multimeter, but one capacitor is found open-circuited across its terminals. The fault is eliminated after capacitor replacement.

ConclusionWhen the above symptoms occur, first identify the faulty section before determining the root cause.

Fault SymptomAfter powering the actuator and applying a CLOSE signal (4mA), the actuator first runs fully open, then fully closed.

Fault Diagnosis and TroubleshootingRemove the servo board and apply power directly to the actuator; the same fault remains. Resistor values are normal, and motor winding resistance is also normal. It is inferred that the capacitor may be defective. The fault is resolved after capacitor replacement.

ConclusionFor this problem, resistors and capacitors should be suspected first.

III. Other Faults

Fault SymptomOnce AC220V power is applied on-site, the protection switch trips immediately, and the servo fuse of the actuator is blown.

Fault Diagnosis and TroubleshootingMotor winding resistance measures near zero, indicating a short circuit. Brake resistance measures near infinity, indicating brake failure (normal value approx. 1.45 kΩ).Solution: Replace the brake and motor, install a new fuse on the servo board, and recommission. Normal operation is restored.

ConclusionThis condition is caused by a faulty brake locking the motor without timely detection, resulting in prolonged stall and overheating, which eventually damages the inter-phase insulation of the motor. (PSQ700)

Fault SymptomThe actuation direction of the actuator is not controlled by the input signal.

Fault Diagnosis and TroubleshootingCurrent-limiting resistors and phase-shifting capacitor show no abnormality. Motor winding resistance measures 1.45 MΩ with frequent fluctuations, indicating abnormal windings. The motor is replaced to resolve the fault. (PSQ200)

Fault SymptomThe actuation direction of the actuator is not controlled by the servo board.

Fault Diagnosis and TroubleshootingThe user is instructed to measure the two current-limiting resistors, phase-shifting capacitor, and motor winding resistance. Results match the standard values provided. No other potential causes exist.Tian Guangri happened to be in Hangzhou and inspected the unit on site, finding one current-limiting resistor open-circuited. A replacement was sent from the factory.This case shows that some users do not fully cooperate with troubleshooting, and reported conditions may differ from reality.Three factors affect actuator rotation direction:① Motor (PSL208) winding② Current-limiting resistors③ Phase-shifting capacitorAll such cases shall be analyzed from these three aspects.

Fault SymptomThe motor does not actuate regardless of the input signal.

Fault Diagnosis and TroubleshootingDirect power to the motor windings results in no rotation. The brake is removed and power reapplied; still no rotation. Winding resistance is normal, and manual handwheel operation is smooth.Suspicion falls on the rotor. Disassembly reveals a solid layer of dust between the rotor and end cover, preventing rotation. After cleaning and lubrication, the rotor turns freely. The motor is reassembled and tested normally.

ConclusionThis is a special case caused by heavy on-site dust. With poor sealing, carbon dust enters and solidifies at high temperature between the rotor and upper end cover, creating resistance greater than the motor starting torque.(Dust enters the housing and reaches the rotor through the central bore of the brake.)

IV. PS Mechanical Faults

Fault SymptomAfter powering the PS208, when a 20mA signal is applied for movement from fully closed to fully open, the motor runs but the feedback signal lags by about ten seconds. Total travel time is double the normal duration.

Fault Diagnosis and TroubleshootingSymptoms clearly indicate a mechanical transmission fault. Upon opening the housing, a large amount of iron filings is found on the gears. All eight lead screw fixing screws are broken, some worn into filings. The lead screw is pushed out by the copper sleeve, and its gear disengages from the motor pinion, causing transmission lag.Gears are cleaned and reinstalled; new screws secure the lead screw. The fault is eliminated.On-site information indicates the control valve leaked, so workers frequently forced the handwheel to close it. The close limit switch was improperly adjusted and failed to limit travel, breaking the screws and damaging the actuator.

ConclusionFor such mechanical faults, the housing must be opened for thorough inspection. Root cause analysis shall be performed after repair to prevent recurrence.

Fault SymptomAfter powering the PSL208, the motor runs but the output shaft does not move, and the feedback value remains unchanged. The output shaft moves when operated manually via the handwheel.

Fault Diagnosis and TroubleshootingThe fault is clearly in the mechanical transmission. Upon opening the housing, the primary reduction gear is found damaged. The motor drives the large gear, but the small gear slips and does not rotate, resulting in motor rotation without output shaft movement. The fault is resolved after gear replacement.

ConclusionThe fully closed position of the control valve was improperly adjusted, causing the valve stem to jam against the seat and vibrate. The motor remained energized and eventually damaged the gear.The close limit switch must be properly set to ensure tight shutoff and rapid power cutoff after reaching the position.

Fault SymptomAfter powering the PS208 actuator, a 4mA signal is applied for movement from fully open to closed. The motor stalls at mid-position and cannot be turned even via the handwheel.

Fault Diagnosis and TroubleshootingThe gear mechanism is intact, so the fault is likely due to deformed or worn output shaft components. Jamming occurs at mid-travel, confirming a problem with the copper sleeve and lead screw. The fault is eliminated after installing a new copper sleeve.

ConclusionThe output copper sleeve is softer than the lead screw and often damaged due to non-standard installation and valve connection. In some cases, both the lead screw and sleeve are damaged.After replacement, strict attention must be paid to installation and connection to avoid sleeve damage.

SCHIEBEL Series

SymptomThe actuator operates normally in local control. When switched to remote control, OPEN is normal but CLOSE fails. Switching back to local also results in no operation. The fuse is found blown.

Troubleshooting ProcedureAfter fuse replacement, the same fault recurs, suggesting an abnormal CLOSE signal from the host controller. The CLOSE signal line is shorted to ground at the control room.Inspection reveals damaged insulation on the CLOSE signal wire at the SCHIEBEL connection, causing a short to the external copper sleeve. After re-insulating and reinstalling the fuse, the unit operates normally.This case shows not all faults are quality issues of our products; specific analysis is required.(Refer to service report for serial number.)

Fault Symptom of FALLSAFE Fail‑safe ActuatorThe actuator does not actuate in either remote or local control.

Troubleshooting ProcedureLong-term on-site service rules out wiring faults. The motor or brake is suspected.The customer measures motor terminal resistance. Heavy rust forms between the brake and motor, making disassembly difficult. After tapping and lubrication, the unit is separated. The motor runs when powered, confirming the brake had locked the rotor.Both units are repaired by derusting and lubrication due to harsh and corrosive on-site conditions.

Fault Symptom: Motor Does Not ActuateTroubleshooting ProcedureA. Check secure and reliable wiring, including power cables, 4–20mADC signal cables, fuses, etc.B. Check the LED indicators:

Thermal switch: TEMP

Torque switches: DER, DEL

Position switches: WER, WELC. Check phase sequence error indicated by the PS LED.Solution: Swap any two phase lines.If still inoperative, the SV board is faulty.Solution: Disconnect black, brown, and green wires from L1, L2, L3 on relay K2 (bypass SV board).Case: Pingxiang Steel PlantD. Check the AC contactor for smooth operation and proper engagement.E. Check motor windings for equal resistance.F. For fail-safe actuators, inspect the brake.

Fault SymptomMotor runs normally but cannot drive the valve.

Troubleshooting ProcedureA. Internal fault of the manual handwheel assembly.The manual drive is not disengaged, preventing electric operation.Case: Henan Lengbian Steel Section PlantB. Check for damage to the plastic gear meshed with the motor gear.High temperature or unactivated torque switch causes stalling and wear of the plastic gear.