UPS 750 Uninterruptible Power Supply Caterpillar

Pre-Removal Steps for the FPU

The following steps are defined for electrical high risk maintenance of the cabinet components that are located behind the locked doors. Follow the steps before performing maintenance on internal components. All AC and DC input to the FPU cabinet must be shut down to perform the operation. The customer load will be unprotected.

The FPU cabinet has two sources of voltage, control AC voltage and the DC bus.

1. Brake the flywheel. Brake the flywheel if the unit is going to be shut down over 20 minutes. Use "Control-X" in UPSView to break the flywheel.

2. Verify that braking is complete. The flywheel must be at zero RPM to continue.

3. Put the cabinet into internal bypass. Turn the key on the FPU cabinet to "Bypass".

4. Discharge the DC bus. Let the DC bus discharge to below 24 VDC.

5. Unlock and open the doors. Open the doors of the cabinet by using a hex key on the upper and lower latches.

6. Discharge the capacitors. Allow the capacitor banks in the UPS to discharge for 5 minutes.