Applicable Models:
AOTDLATT, AOTDLBTT, and AOTG**LATT
Purpose
This procedure provides a step-by-step guide for testing the Power Factor Correction (PFC) PCB.
The PFC PCB ensures electrical efficiency by regulating current flow within the inverter circuit. A faulty PFC can cause breaker tripping upon system start-up
PFC testing
.Symptoms of PFC PCB Failure
Circuit breaker trips immediately when the system is energized.
No power to the control PCB.
Visible damage or burn marks on the board components.
Testing Overview
Testing the PFC PCB follows a similar process to IPM (Intelligent Power Module) testing, but the presence of choke coils in the circuit makes the measurement more sensitive and requires precision.
A multimeter with diode-check function is mandatory for accurate testing
PFC testing
.Test Points and Connections
Refer to the board diagram (page 1) for the labeled test points:
Orange terminal (TM504): Positive test terminal.
Purple terminal (TM505): Negative test terminal.
Other test points: TM500, TM501, TM502, TM503.
Ensure the PCB is fully disconnected from power before testing.
Test Procedure
Set the multimeter to the diode test mode.
Use the red lead on TM504 (positive) and black lead on each of the corresponding test points.
Record the readings according to the table below:
| Red Lead | Black Lead | Expected Reading |
|---|---|---|
| TM504 | TM500 | OL |
| TM504 | TM501 | OL |
| TM504 | TM502 | OL |
| TM505 | TM500 | 0.4 V |
| TM505 | TM501 | 0.4 V |
| TM505 | TM502 | 0.4 V |
| TM501 | TM504 | 0.4 V |
| TM502 | TM504 | 0.4 V |
| TM503 | TM504 | 0.4 V |
| TM502 | TM505 | OL |
| TM503 | TM505 | OL |
(As shown on page 2 of the document.)
Results and Interpretation
Normal Operation: The expected readings should be as per the table above (0.4 V for forward-biased diodes, OL for open circuits).
Failure Condition: A reading of 0.0 V indicates a short circuit in the PCB — the PFC board is faulty and must be replaced
PFC testing
.
Safety Note
Always isolate power supply before testing.
Discharge capacitors to avoid electric shock.
Handle components carefully to prevent static discharge damage.
Summary
This procedure verifies the operational integrity of the PFC PCB in Fujitsu outdoor inverter systems.
If any test result deviates from the expected readings, the PFC board must be replaced before re-energizing the system.