Woodward EM-80/EM-300 actuator system

Electromagnetic Compatibility (EMC) and Cabling

For a system operating with high-frequency switching electronics, EMC compliance is paramount to prevent interference with other shipboard or plant equipment.

Cabling Strategy

All system wiring must utilize shielded cabling.

• Motor/Power Lines: These carry high interference potential. The shield must be grounded at both ends to the frame ground.

• Resolver/Feedback Cables: These are sensitive. The shield must be grounded at both ends to prevent magnetic or high-frequency noise from affecting position data.

• Signal Lines: 4–20 mA command and 1–5 V feedback cables must also be shielded.

Grounding Philosophy

The manual advises against classical “star” grounding for high-frequency noise reduction. Instead, a reference surface (e.g., a bare, metallic mounting plate) linked to the devices’ frame grounds over a wide area is preferred.

• Connection Lengths: Ground conductors should be as short as possible (ideally < 30 cm).

• Contact: Remove paint, varnish, or other insulating layers from grounding points. Use serrated lock washers to ensure permanent conductive contact.

Line Filter Considerations

An EMI filter (P/N 1326-1125) is required for marine systems using grounded power networks (TN or TT). However, it is NOT recommended for isolated power networks (IT) common in some marine or land-based applications. The filter’s internal RC networks can cause safety issues or nuisance faults when used with insulation monitors on IT systems.

System Configuration and Customization

The EM driver (specifically version 3522-1042) is field-configurable via the front keypad. This allows technicians to adapt the driver to specific application needs without special software tools.

Motor Type Selection (P11)

Because the driver supports both EM-80 and EM-300 actuators, the user must select the correct motor type via parameter P11 (0 for EM-80, 1 for EM-300). Failing to do so will result in incorrect torque limiting or fault codes (e.g., “Wrong Actuator” fault for EM-80 or “Pot Out of Range” for EM-300).

Rotation Sense (P10)

Parameter P10 allows the selection of clockwise (CW) or counter-clockwise (CCW) rotation to match the mechanical linkage setup.

E-Stop Logic (P14)

The behavior of the E-Stop input can be inverted. Setting P14 to 0 enables “E-Stop = LOW” (safe state), meaning a broken wire will drive the actuator to the minimum position. This is the recommended setting for safety.

Fault Behavior (P15 - Fault #64)

Fault #64 is triggered when the position demand signal falls below 3.6 mA. By default, this is a latching fault (the motor will not restart even if the signal returns).

• Alarm Mode (P15=1): No reset required. If the signal returns, the motor moves.

• Fault Mode (P15=3): Reset required.

• Caution: In Alarm Mode, the actuator can move suddenly when the signal returns. Personnel must be clear of the linkage during such recovery sequences.

Troubleshooting and Maintenance

The EM-80/EM-300 system is designed to be largely maintenance-free. The gearbox is sealed and does not require oil changes unless operated continuously at the maximum temperature of 85°C, in which case oil replacement is advised at five-year intervals.

Electrical Troubleshooting

When diagnosing faults, specific resistance checks on the driver terminals can isolate the issue to the actuator, cable, or driver.

Motor Windings (Connector X20):

• U to V, V to W, W to U should read approximately 0.5 Ω.

Resolver Connector (X140):

• Pins 1 to 2 (Sin+ to Exc-): ~65 Ω

• Pins 5 to 9 (Exc+ to Sin-): ~85 Ω

• Pins 7 to 8 (Temp+ to Temp-): ~85 Ω

Potentiometer (EM-300 only, round connector on actuator):

• Verify resistance at the mid-position (20 degrees). For example, at mid-stroke, resistance between specific pot pins should be around 5400 Ω. Significant deviation indicates a faulty potentiometer or wiring.

Common Fault Codes

The driver LCD provides alphanumeric fault codes to aid diagnostics:

• Fault #31 (Short/Ground): Hardware short-circuit switch-off. Check motor windings and cable integrity.

• Fault #33 (Overcurrent): Total motor current exceeded limits. Check for binding load or shorted motor phases.

• Fault #37 (Encoder): Error due to encoder. Check resolver cable connections and shielding. EMI is a frequent cause.

• Fault #41 (TempMotor TMS): Motor temperature sensor reports over-temperature. Check ambient temp and cooling; ensure load torque is within specs.

• Fault #64 (Pos DMD lost): 4–20 mA input < 3.6 mA. Check control system output and wiring.

• Fault #66 (3 Phase Off): Only applicable if redundancy is used; indicates loss of 3-phase power.

Power Redundancy (Appendix D)

For mission-critical applications, the EM driver supports a power redundancy scheme. If the primary 3-phase power fails, the system can switch to a single-phase backup power source (230 Vac) to maintain operation.

• Sequence: 1. Loss of 3-phase (Alarm #66). 2. Switch to single-phase (within 140 ms). 3. Wait for voltage stabilization. 4. Restore 3-phase (within 40 ms of dropping single-phase).
  This capability ensures the engine continues to run even during primary power anomalies.