General Assist Technical Reference
Filter PCB - CT Testing and Verification
Part No. 9705256026
Current Transformer (CT) resistance, connector and output-voltage checks
Purpose: Verify correct current detection and signal transmission from the Current Transformer (CT) to the Controller PCB through the Filter PCB.
Safety: Electrical testing must be completed by suitably qualified personnel. Isolate power before resistance, connector or continuity checks. Live voltage measurements must only be carried out using appropriate safe working procedures.
1. Connector Inspection
- Verify that CN202 on the Filter PCB and CN11 on the Controller PCB are securely connected.
- Check both connectors for loose, corroded or damaged pins.
- Inspect the wiring harness between CN202 and CN11 for continuity and correct colour matching: Red → Red.
2. CT Resistance Verification
Measure the terminal resistance through the CT circuit between CN11 (Controller PCB) and CN202 (Filter PCB).
Expected resistance: approximately 110 Ω
- A resistance reading significantly higher or lower than approximately 110 Ω indicates an abnormal CT circuit or Filter PCB.
- Action: Replace the Filter PCB if the resistance reading is outside specification.
3. CT Output Voltage Reference
Measure the voltage across CN11 while the system is operating and compare the reading with the detected current.
| Voltage (mV) | Detection Current (A) |
|---|---|
| 400 | 5.6 |
| 561 | 6.9 |
| 737 | 8.4 |
| 948 | 10.0 |
| 1187 | 12.0 |
| 1525 | 14.7 |
| 1721 | 16.2 |
| 1971 | 18.2 |
| 2231 | 20.2 |
| 2495 | 22.3 |
| 2720 | 24.0 |
| 3001 | 26.1 |
| 3246 | 28.0 |
Reference values only: The voltage should rise proportionally with current. If the voltage output does not correspond with the measured current, the CT or Filter PCB may be faulty. Always take readings under stable operating conditions.
4. Test Summary
| Check | Test Item | Expected Value | Action if Abnormal |
|---|---|---|---|
| 1 | CN202 / CN11 connection | Secure, no corrosion or pin damage | Reconnect, repair wiring or correct connector issue |
| 2 | CT resistance | Approx. 110 Ω | Replace Filter PCB if outside specification |
| 3 | CT output voltage | Corresponds with detected current using reference table | Investigate CT or Filter PCB; replace defective component |
Key diagnostic value: A normal CT circuit should show approximately 110 Ω resistance and an output voltage that increases consistently with detected current.