Carrier PIC 5+ - Page 20

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Fig 8 – VFD cabinet view (example of LF2 4AA)
1. Circuit breaker/main disconnect switch (QF101) for the following functions:
- Short-circuit protection of the main circuit
- Single connection point of the installation power cables
- Isolation and shut-down of the machine, using the handle accessible on the outside of the control box
- Emergency stop, initiated by the PIC control
2. Filter CEM RFI (ZGS) to limit high-frequency conductor interferences (>150 kHz).
3. Power safety contactor (K101)
4. Power transformer (T1) and fuse (FU10) for the internal control circuit of the variable-frequency drive.
5. Surge limiter (F).
6. Power supply circuit protection disconnect switch for the PIC control box (QF).
7. Load resistor shunt capacitors (K1-). They short-circuit the load resistors when the capacitors are loaded.
8. Capacitor resistors (R1-3C) and coils for inlet filtering of the main circuit
9. Power module and associated control interface board (GS) for the following functions:
- Compressor start-up and shutdown by voltage/frequency ramping to permit limiting of the couple and inrush current at start-up
- Control of the voltage/frequency applied to the compressor
- All electrical compressor protection devices
- All devices to protect against internal faults of the variable-frequency drive as well as pressure safety switch cut-out and re-starting the oil pump
- Report of variable-frequency drive status parameters and internal faults to the PIC control.
10- Terminal connections (XP), I/O with chiller (Gatekill chain from pressure switches terminals, run feedback, com… )
11. Communication gateway board. Provides the communication interface between the variable-frequency drive and the PIC control.
12. Load resistors of the main power circuit (R4-6C) and protection fuses of the load circuit (FU**). To limit the inrush current while power is
supplied to the variable-frequency drive.