The primary set of three Current Transformers surrounds each phase of the output bus bars in the top part of the cabinet. The primary Current Transformer ratio is 2000:5.
The secondary set of three Current Transformers takes the output of the primary Current Transformers and further reduces the current that is fed to the External Source Sync Board in a 5:0.1 ratio. These Current Transformers are located on the fan plenum shield, above the fans in version 1 hardware and on the top component panel in version 2 hardware.
Current from the secondary Current Transformers is sent as signals to the ESS on the fan plenum shield, which is used to meter the output power of the 4-Wire Transformer and send the information to the APC-2 via the Multi-Drop Network.
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| Illustration 1 | g01272289 |
4-Wire Transformer Cabinet Current Transformer Locations, Version 1 Hardware (1) Primary Current Transformers (2) Secondary Current Transformers | |
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| Illustration 2 | g01272291 |
4-Wire Transformer Cabinet Current Transformer Locations, Version 2 Hardware (1) Primary Current Transformers (2) Secondary Current Transformers | |
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| Illustration 3 | g01272293 |
Removal Groups (Primary Current Transformer) | |
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| Illustration 4 | g01272311 |
Phase A Primary Current Transformer Removal Parts (5) Frame (6) Red Insulating Spacer (7) Horizontal Bus Bar (8) Vertical Bus Bar (9) Transformer Output Bus (10) Red Insulating Frame Cross-Brace | |
Primary Current Transformer Removal
The Primary Current Transformers fall in three removal groups. Refer to Illustration 3 for the group locations. Each removal group is made up of the following components: Current Transformer, Vertical Bus Bar (8), Horizontal Bus Bar (7), Red Insulating Spacer (6), Red Insulating Frame Cross-Brace (10), Transformer Output Bus (9) and Transformer Output Bus Frame. Refer to Illustration 4.
The following removal steps are for the Phase A Primary Current Transformer removal. The removal of the Primary Current Transformer on the other phases is similar.
- Perform steps in the Systems Operation, Testing and Adjusting, "Internal Component Preremoval Steps (4 Wire Transformer Cabinet)" in order to de-energize the system and gain access to internal components.
- Remove the four bolts (15) that hold the Vertical Bus Bar to the 4-wire transformer outputs.
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| Illustration 5 | g01272321 |
- Remove the two bolts (16) that hold the Vertical Bus Bar to the Red Insulating Frame Cross-Brace.
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| Illustration 6 | g01272323 |
- Remove the three (17) bolts that hold the Vertical Bus Bar to the Horizontal Bus Bar.
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| Illustration 7 | g01272325 |
- Move the Vertical Bus Bar downward, out of the way.
- Remove the two bolts (20) that hold the Red Insulating Spacer to the Horizontal Bus Bar.
Note: Removal of the Phase C (lower left) Primary Current Transformer requires the removal of two Red Insulating Spacers.
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| Illustration 8 | g01272326 |
Red Insulating Spacer Assembly | |
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| Illustration 9 | g01272383 |
Spacer Hardware Connections (20) Bolt (21) Split Washer (22) Washer | |
- Remove the two cross tip screws that hold the Current Transformer to the red corner bracket and to the Horizontal Bus Bar.
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| Illustration 10 | g01272328 |
- Remove the two wires that connect to the "X1" and "X2" terminals of the Current Transformer. The wires locations are labeled. Verify the labeling. Refer to Illustration 14.
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| Illustration 11 | g01272422 |
- Slide the Current Transformer off the Horizontal Bus Bar to the right.
Primary Current Transformer Installation
- Slide the Current Transformer onto the Horizontal Bus Bar from the right, with the "H1" side facing the left and the two "X1" and "X2" terminals on the front at the top.
- Attach the Current Transformer to the red corner bracket and Horizontal Bus Bar with the following fasteners: two cross tip screws, two washers and two nuts. Refer to Illustration 13 for hardware connections.
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| Illustration 12 | g01272328 |
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| Illustration 13 | g01272384 |
Current Transformer Hardware Connections | |
- Attach the "X1" and "X2" wires to the two terminals. The wires locations are labeled. See Illustration 14 for wire connections.
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| Illustration 14 | g01272422 |
- Attach the Red Insulating Spacer to the Horizontal Bus Bar rail with two bolts/washers. Refer to Illustration 16 for hardware connections.
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| Illustration 15 | g01272326 |
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| Illustration 16 | g01272383 |
Spacer Hardware Connections (20) Bolt (21) Split Washer (22) Washer | |
- Attach the Vertical Bus Bar to the Horizontal Bus Bar with three bolts/washers/ nuts. Insert the bolts from the bottom side of the bus bar.
Refer to Illustration 17 and Illustration 18 for hardware connections.
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| Illustration 17 | g01272325 |
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| Illustration 18 | g01326837 |
(25) Nut (26) Belleville Washer (27) Grade 8 Coated Steel Washer (28) Bus Bars (29) Bolt | |
- Attach the Vertical Bus Bar to the transformer outputs with four bolts/washers/ nuts. Insert the bolts from the back side of the bus bar.
Refer to Illustration 19 and Illustration 18 for hardware connections.
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| Illustration 19 | g01272321 |
- Attach the Vertical Bus Bar to the Red Insulating Frame Cross-Brace with the following fasteners: two bolts, two washers and two nuts. Insert the bolts from the back side of the bus bars.
Refer to Illustration 20 and Illustration 18 for hardware connections.
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| Illustration 20 | g01272323 |
- Tighten the bus bar to bus bar nuts to 150 N·m (110 lb ft).
Note: Always tighten the hex nut, not the bolt.
Secondary Current Transformer Removal
- Perform steps in the Systems Operation, Testing and Adjusting, "Internal Component Preremoval Steps (4 Wire Transformer Cabinet)" in order to de-energize the system and gain access to internal components.
- Remove the four wires that connect to the "H1", "H2", "X1" and "X2" posts of the Current Transformer. The cables locations are labeled. Verify the labels.
- Remove the four cross tip screws that attach the Current Transformer to the fan plenum panel.
- Remove Current Transformer from cabinet
Secondary Current Transformer Installation
- Position the Current Transformer on the fan plenum panel in the position and orientation indicated by Illustration 21.
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| Illustration 21 | g01272395 |
- Attach the Current Transformer to the fan plenum panel with four cross tip screws.
- Attach the four cables to the "H1", "H2", "X1" and "X2" posts of the Current Transformer. Refer to Illustration 21 for wire connections.