General Assist Technical Reference
Active Filter Check (ACTPM)
Active filter circuit identification and current path
Technical reference for identifying ACTPM terminals and understanding the active filter circuit.
What is the ACTPM?
The ACTPM is the Active Filter Circuit PCB. Its purpose is to improve the power factor of the DC supply to the inverter system.
The ACTPM is the Active Filter Circuit PCB. Its purpose is to improve the power factor of the DC supply to the inverter system.
Electrical safety: This circuit operates within the high-voltage DC section of the outdoor unit. Isolate power and allow the DC bus to discharge before carrying out inspections or resistance checks. Testing on live equipment must only be performed by appropriately qualified personnel using suitable test equipment.
1. ACTPM function
- The PCB is referred to as the ACTPM.
- Its primary purpose is to increase the power factor of the DC output supplied to the inverter system.
- The positive polarity passes through the ACTPM and the choke coil.
- A control harness connects the ACTPM to the Main / Controller PCB.
- The negative polarity (ground) to N is not altered by the ACTPM circuit.
2. Terminal identification
| Terminal | Function |
|---|---|
| − / − IN | Negative DC input / reference. Model labelling may vary. |
| + / + IN | Positive DC input to the ACTPM circuit. Model labelling may vary. |
| L1 | Connection associated with the positive path through the active filter / choke circuit. |
| L2 | Return connection from the active filter / choke circuit. |
| P | Positive DC output toward the inverter DC bus. |
| N / N1 | Negative DC connection. The negative polarity is not altered by the ACTPM circuit. |
Current path overview
Positive (+) → ACTPM → L1 → Choke Coil → L2 → P → Inverter DC Bus
Negative (−) → N / N1 → Inverter DC Bus
Negative (−) → N / N1 → Inverter DC Bus
3. What to check
- Confirm terminal identification. Check the markings on the ACTPM before testing, as labels can vary by model.
- Inspect the positive circuit path. Check connections from the positive input through the ACTPM, L1, choke coil, L2 and P output.
- Inspect the negative circuit. Confirm the N / N1 path is secure and has not been altered or damaged.
- Check the choke coil and harness connections. Loose, burnt or damaged terminals can interrupt the active filter circuit.
- Check the control harness. Ensure the ACTPM control harness is correctly connected to the Main / Controller PCB.
4. Important notes
- ACTPM terminal names are model dependent.
- The input terminals may be labelled − / − IN and + / + IN.
- The negative output may be labelled N or N1.
- Always confirm the circuit against the applicable service documentation for the specific model before replacing components.