UPS 250, UPS 300, UPS 500, UPS 600, UPS 750 and UPS 900 Uninterruptible Power Supply Caterpillar

DC Bus Capacitor Remove/Replace Procedure (Pre-2.4 Hardware)

Prior to conducting any work, ensure that the MMU is de-energized, the flywheel is at 0 RPM, and the DC Bus has bled down to 0 VDC.

1. Remove the Field Coil Driver Module as per the instructions given in the Removal Procedure under the Field Coil Driver topic in this manual.

2. Remove the Phase "A" and "B" flywheel inverters as per the instructions given in this manual.

   Note: Remove Capacitors front-to-back and install back-to-front, to have more room to work and to have greater visibility of the work being done.

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Illustration 1	g03404443

3. Remove the 12x HI/LOW DC Bus fuses from the left-hand side of the DC Bus.

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Illustration 2	g03393019

4. Remove #6 HI/LOW neutral leads from the DC bus capacitors, using a 4 mm (5/32 inch) Allen wrench.

5. Remove the #6 HI/LOW Resistor from the DC Bus capacitor, using a 4 mm (5/32 inch) Allen wrench.

6. Remove the #6 HI/LOW Fuse Holders from the DC bus capacitors, using a 4 mm (5/32 inch) Allen wrench.

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Illustration 3	g03390957

7. Remove the #6 HI/LOW nylon mounting nuts from the right-hand side of the DC Capacitors using a 3/4 inch socket. Keep the nylon nut to utilize during installation.

8. Slide out the #6 HI/LOW Capacitors along the diagonal mounting track.

Illustration 4	g03387642
20093 CAP, ALUM, 7200uf, 500VDC, 20%

Illustration 5	g03392378
Capacitor Orientation: Positive on top

Illustration 6	g03387644
DC Capacitor Insulator 78.0 mm (3.07 inch)

Note: Remove Capacitors front-to-back and install back-to-front to have more room to work and to have greater visibility of the work being done.

1. Install #6 CAP, ALUM 7200uf LOW capacitor and capacitor insulator (Reuse the original 40243 insulator) along the bottom of the capacitor bank. Capacitor insulator will be placed between the capacitor and the mounting bracket.

2. Tighten, but do not torque, the nylon mounting nut on the right-hand side of the capacitor. This will assist in aligning the left-hand mounting hardware.

3. Install the #6 LOW resistor lower 14 mm bolt using a flat washer and split washer. Torque prior to installing the remaining hardware.

4. Tighten the 14 mm hex bolt to a torque of 21.0 N·m (185.9 lb in).

5. Install #6 LOW Fuse Holder 14 mm bolt using a flat washer and a split washer - passing through the neutral lead, the resistor, and then the fuse holder.

6. Install #6 LOW Fuse Holder upper 14 mm bolt using a flat washer and a split washer.

7. Tighten the 14 mm bolts mentioned in steps 4 and 5 to a torque of 21.0 N·m (185.9 lb in).

8. Tighten the 3/4 inches nylon mounting nut to a torque of 180.0 N·m (132.8 lb ft).

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Illustration 7	g03392379

9. Install #6 CAP, ALUM 7200uf HI Capacitor and the capacitor insulator (40243) along the top of the capacitor bank.

10. Tighten, but do not torque, the nylon mounting nut on the right-hand side of the capacitor. This will assist in aligning the left-hand mounting hardware.

11. Install #6 HI Resistor upper 14 mm bolt using a flat washer and split washer.

12. Install #6 HI Fuse Holder upper 14 mm bolt using a flat washer and a split washer - passing through the neutral lead, the resistor, and then the fuse holder.

13. Install the #6 HI Fuse Holder lower 14 mm bolt using a flat washer and a split washer.

14. Tighten the 14 mm hex bolts to a torque of 21.0 N·m (185.9 lb in).

15. Tighten 3/4 inches nylon mounting nut to a torque of 180.0 N·m (132.8 lb ft).

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Illustration 8	g03391759

16. Repeat the installation procedure steps 1 through 15 for the remaining #1-5 HI/LOW Capacitors, working from back to front.

17. Install the Field Coil Driver (FCD) module as per the installation procedure given under the topic "Field Coil Driver" in this manual.

18. Install the AØ and BØ flywheel inverters, as per the installation procedure given under the topic "Flywheel Inverter Assembly" in this manual.

19. Initialize power to the system - in BYPASS - as per the instructions given in this manual.

20. Calibrate the DC Bus as per the instructions given in the manual.