REPLACEMENT KIT INSTRUCTIONS NRU Diode Bridge Assembly Replacement (180-350A DC) Contents In 180A DC and 350A DC NRUs, all 6 diodes (D1 - D6) and the both the positive and negative heatsinks (HS1 - HS2) can be replaced together as a single unit. This publication describes how to replace the diode bridge assembly in 180A DC and 350A DC non-regenerative, front-end units (NRU). What This Kit Contains Using the table below, verify that you have received the appropriate items in your kit: For this part: You should receive this quantity: diode bridge assembly 1 Other Items Needed Before you begin, be sure you also have the following: Whatever tool(s) you will need to: Remove and connect line fuses and AC busbars Disconnect and connect wires Remove, loosen, and/or tighten bolts Torque bolts Documentation: Your drive system schematics Publication 2364E-5.01, Non-Regenerative DC Bus Supply (NRU) User Manual Allen-Bradley Motors
2 NRU Diode Bridge Assembly Replacement (180-350A DC) Safety Precautions The following general precautions apply to NRUs and their respective drive systems:! ATTENTION: Only those familiar with the drive system, the products used in the system, and the associated machinery should plan or implement the installation, startup, and future maintenance of the system. Failure to comply can result in personal injury and/or equipment damage. ATTENTION: Verify that all sources of AC and DC power are deenergized and locked out or tagged out in accordance with the requirements of ANSI/NFPA 70E, Part II. ATTENTION: The system may contain stored energy devices. To avoid the hazard of electrical shock, verify that all voltage on capacitors has been discharged before attempting to service, repair, or remove a drive system or its components. You should only attempt the procedures in this manual if you are qualified to do so and are familiar with solid-state control equipment and the safety procedures in publication NFPA 70E. ATTENTION: When servicing any unit, do not drop any nuts, bolts, washers, etc. inside the unit as they may cause a short circuit on power up. Dropped items must be found and removed before you apply power. ATTENTION: This drive system contains ESD (Electrostatic Discharge) sensitive parts and assemblies. Static control precautions are required when installing, testing, or repairing this assembly. Component damage can result if ESD control procedures are not followed. If you are not familiar with static control procedures, refer to Rockwell Automation publication 8000-4.5.2, Guarding Against Electrostatic Damage or any other applicable ESD protection handbook. Special Instructions The following special instructions apply to NRUs and their respective drive systems: Important: As you remove parts, place them in order on a clean surface because you will need to reuse some of them during reassembly. Important: Some washers, such as the diode clamp washers and the Belleville washers used on busbar bolts have only one correct orientation.
NRU Diode Bridge Assembly Replacement (180-350A DC) Removing the Diode Bridge Assembly 3 This section contains the procedure for removing the diode bridge assembly. 1. Disconnect AC busbars at arrows shown in Figure 1. Figure 1 Illustration of Where to Disconnect AC Busbars 2. Disconnect both of the "Heatsink-Over-Temperature" switches, at the quick-disconnect connectors located near the top of the left heatsink. Refer to arrow in Figure 2. Figure 2 Location of Connectors for Heatsink Overtemperature Switches Allen-Bradley Motors
4 NRU Diode Bridge Assembly Replacement (180-350A DC) 3. Disconnect the wire between suppressor diode D11 at the center top of the left heatsink. 4. Disconnect the wire between suppressor capacitor C11 at the center top of the right heatsink. 5. Disconnect the DC output power wires from the heatsink busbars located near the bottom of the right heatsink. Refer to arrows in Figure 3. Figure 3 Location of DC Power Connections 6. Disconnect the DC output-low power wires from the heatsink busbars located near the bottom of the right heatsink. Refer to arrows in Figure 4. Figure 4 Location of Output-Low Power Wire Connections
NRU Diode Bridge Assembly Replacement (180-350A DC) 5 7. Loosen, but do not remove, the 2 lower bolts that hold the heatsink red Glastic L-brackets to the subpanel. 8. While supporting and preventing the heatsink from falling forward, remove the 2 upper bolts that hold the heatsink red Glastic L-brackets to the subpanel. Note: The diode bridge assembly weighs approximately 25 lb (11kg). 9. Lift the diode bridge assembly up and off of the 2 loosened lower bolts and place the assembly on a suitable surface. Refer to Figure 5 for photograph of removed bridge. Figure 5 Diode Power Bridge With AC Line Fuses and Bus Attached 10. Remove the AC busbars and line fuses attached to the bridge. Refer to Figure 6 for a photograph of the bridge without AC busbars and line fuses. Allen-Bradley Motors
6 NRU Diode Bridge Assembly Replacement (180-350A DC) Figure 6 Power Bridge Without AC Busbars and Line Fuses Installing the Diode Bridge Assembly Follow this procedure to install the diode bridge assembly. 1. Reconnect AC busbar/line fuse assembly to the bridge assembly and torque bolts to 25 lb-ft (34 N-m). Refer to Figure 5. 2. Position and hold the new diode bridge assembly on the 2 loosened lower bolts. Note: The diode bridge assembly weighs approximately 25 lb (11kg). 3. While supporting and preventing the heatsink from falling forward, install the 2 upper bolts that secure the diode bridge assembly s red Glastic L-brackets to the subpanel. 4. Tighten the 2 lower bolts that hold the heatsink red Glastic L-brackets to the subpanel. 5. Reconnect the DC output-low power wires to the heatsink busbars located near the bottom of the right heatsink (Refer to Figure 4). 6. Reconnect the DC output power wires to the heatsink busbars located near the bottom of the right heatsink (Refer to Figure 3). 7. Reconnect the wire between suppressor capacitor C11 at the top of the right heatsink. 8. Reconnect the wire between suppressor diode D11 at the top of the left heatsink.
NRU Diode Bridge Assembly Replacement (180-350A DC) 7 9. Reconnect both of the "Heatsink-Over-Temperature" switches, at their respective quick-disconnect connectors located near the top of the left heatsink (Refer to Figure 2). 10. Reinstall AC line fuses F1, F2, and F3 and their respective AC input busbars (Refer to Figure 1). Torque bolts to 25 lb-ft (34 N-m). 11. Dispose of the removed part according to your company s procedures and local ordinances. Allen-Bradley Motors
NRU is a trademark of Rockwell International or its subsidiaries. Lexan is a trademark of General Electric Corp. Supersedes Publication 2364E-5.10 - June 1997 P/N 173345 1998 Rockwell International. All Rights Reserved. Printed in USA