Fujitsu General Australia

Overview

This section provides a detailed understanding of key electronic control components and their role within Fujitsu General outdoor and indoor units.
Each component contributes to the conversion, regulation, and control of AC and DC voltages essential for efficient inverter system operation.

1. Diode Bridge (Rectifier)

Function:
Converts incoming AC voltage (230–415V AC) into DC voltage (200–230V DC).
This is the first stage of DC power generation within both single-phase and three-phase systems.

Key Points:

• Supplies DC voltage to the ACTPM or PFC module.

• Must be verified using diode test mode (see Diode Bridge Testing module).

• Typical output (DC):

  • Single Phase: 200–230V DC

  • Three Phase: 560–600V DC

2. Active Filter Module (ACTPM / PFC)

Function:
Improves the power factor and boosts DC voltage output for stable operation.

Process Description:

• Receives rectified DC power from the Diode Bridge.

• Boosts DC voltage from 200–230V to approximately 330–370V DC (single-phase) or 560–600V DC (three-phase).

• Provides stable DC output to the Capacitor Board.

Key Notes:

• Enhances efficiency by reducing harmonic distortion.

• Failure symptoms include breaker tripping, low DC output, or ACTPM overcurrent errors.

3. Capacitor Board

Function:
Smooths pulsating DC voltage from the ACTPM or Diode Bridge, ensuring constant voltage delivery to the IPM (Inverter Module).

Key Points:

• Contains high-voltage capacitors (rated up to 450V DC).

• Stores and releases DC energy during inverter modulation.

• Should discharge safely after power-off — verify using a multimeter before handling.

Expected Output Voltage:

• Single Phase: 330–370V DC

• Three Phase: 560–600V DC

4. Integrated Power Module (IPM) / Transistor Board

Function:
Acts as an inverter, converting stable DC voltage into pulsating DC waveforms to drive the DC compressor.

Operation:

• Uses transistor switching to modulate compressor motor speed.

• Outputs to compressor windings U, V, and W.

• Receives control signals from the Main PCB for frequency and voltage regulation.

Key Points:

• Essential for variable speed control in inverter systems.

• Faults often trigger DC Overcurrent, Compressor Lock, or Inverter Communication errors.

5. Electronic Expansion Valve (EEV)

Function:
Precisely meters refrigerant flow into the evaporator coil according to load conditions.

Operation:

• Operates on 12V DC signals from the Main PCB.

• Controlled by pulse signals to open or close in minute steps.

• Coil resistance varies by type (see EEV Coil Testing module).

6. Pressure Transducer Sensor

Function:
Monitors refrigerant system pressures and converts them into DC voltage feedback for control logic.

Typical Readings:

• Supply: 5V DC

• Output: 0.5V – 4.5V DC corresponding to system pressure.

Applications:

• Used for suction, discharge, and subcool pressures.

• Enables precise load control and system protection.

7. Main PCB (Control Board)

Function:
Central control board that coordinates all subsystems, power stages, and sensor feedback.

Supplies & Signals:

• AC Input: 230V or 415V AC

• DC Input: 330–370V DC (single-phase) / 560–600V DC (three-phase)

• Sensor Power: 5V DC (thermistors, transducers)

• Valve & Fan Power: 12V / 15V DC

Responsibilities:

• Processes temperature, pressure, and communication signals.

• Controls compressor frequency, EEV operation, and fan modulation.

• Interfaces with the indoor unit via the communication signal terminal (Terminal 3).

8. DC Compressor

Function:
Converts electrical energy into refrigerant compression, with speed regulated by inverter frequency.

Operation Details:

• Supplied by IPM with modulated DC pulses to U, V, W windings.

• Resistance between windings: 0.3–2.0Ω (typical).

• Must maintain insulation resistance above 1 MΩ to earth.

Key Component Interconnection Summary