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| Illustration 1 | g03684573 |
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Bypass static switch assembly (1) Static switch snubber board (2) Bypass static switch fuses (3) K4 contactor (4) Static switch driver board (5) Bypass static switch thyristors | |
The bypass static switch assembly is composed of three discrete thyristor modules. One module is connected to each of the input phases. Each module has two devices. In the system, the devices are connected in parallel. However, the devices are connected in opposite directions. The functions of the static switch are as follows:
- Isolation of the input node during a discharge
- Enable a make-before-break transfer to bypass
One of the parallel sets of thyristors is turned on at a time. The thyristors only conduct current when the thyristors are forward biased. Forward biased thyristor operation is used for all three of the phases.
The SSD is located on the front of the bypass static switch assembly and acts as an interface between the UPS and the static switch.
There are three thyristors located on the static switch assembly, one for phase A, one for phase B, and one for phase C. The thyristors allow for rapid changeover when changing between bypass and online states.
The static switch snubber circuit card is connected between the input and output of each of the three static switches. The snubber board prevents false signals that could turn on the static switches. False signals are caused by voltage transients.
The K4static bypass contactor is located behind the left door panel of the SIO cabinet. The K4 controls the static bypass circuit to allow a rapid transfer to bypass.
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| Illustration 2 | g03789056 |
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(9) Bypass static switch fuses
(10) NC leads on fuse sensors | |
- Refer to Systems Operation, Test and Adjust, UENR4695, "Internal Component Pre-Removal Steps". Perform the internal component pre-removal procedure to shut down the system and to gain access to internal components.
- Remove F34 (9), F35 (9), F36 (9), and COM. Remove F34, F35, F36 NC leads from each fuse sensor (10).
- Remove the 3/4 inch nut and bolt that attaches the fuse to the bus.
- Remove the fuses.
- Position the fuse in the cabinet over the stand-offs that are connected to the right panel.
- Install the 3/4 inch nut and bolt that attaches the fuse to the bus.
- Install F34, F35, and F36 COM. Install F34, F35, F36 NC leads to fuse sensor.
Bypass Static Switch Driver Board
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| Illustration 3 | g03685043 |
| (11) Bypass static switch driver board location | |
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| Illustration 4 | g03685044 |
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Bypass static switch driver board (SSD) (12) Board stand-off locations (one not shown) (13) J1 ribbon cable connector (14) 24 V board supply, J3 connector | |
The SSD is located on the front of the bypass static switch assembly and acts as an interface between the UPS and the static switch.
Bypass Static Switch Driver Board Removal
- Refer to Systems Operation, Test and Adjust, UENR4695, "Internal Component Pre-Removal Steps". Perform the internal component pre-removal procedure to shut down the system and to gain access to internal components.
- Disconnect thyristors gating leads.
- Unplug the connector for the J1 ribbon cable (13) and the J3, 24 V supply connector (14).
- Disconnect the eight white plastic stand-offs (12) that mount the board to the panel. Use the following method.
Note: The board must be removed from each stand-off without bending the board.
- Pinch the head of each stand-off so that the board is not locked but is still attached to the stand-off.
- Remove the board by gently and evenly pulling the board from all of stand-offs at the same time.
Bypass Static Switch Driver Board Installation
- Position the board in the cabinet over the eight white stand-offs.
- Push the board, gently and evenly, onto all the stand-offs simultaneously. Make sure all stand-offs are locked in place.
- Plug in connector for the J1 ribbon cable (13) and the J3, 24 V supply connector (14).
- Connect the thyristor gating leads.
Bypass Static Switch Snubber Board
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| Illustration 5 | g03684573 |
| (1) Bypass static switch snubber board location | |
The static switch snubber circuit card is connected between the input and output of each of the three static switches. The snubber board prevents false signals that could turn on the static switches. False signals are caused by voltage transients.
Bypass Static Switch Snubber Board Removal
- Refer to Systems Operation, Test and Adjust, UENR4695, "Internal Component Pre-Removal Steps". Perform the internal component pre-removal procedure to shut down the system and to gain access to internal components.
Show/hide table
Illustration 6 g03685507 (20) J3 connector
(21) J2 connector
(22) J1 connector - Unplug the connectors from J1 (22), J2 (21), and J3 (20).
- Remove the board from the four white plastic stand-offs that connect the board to the panel. Use the following steps.
Note: The board must be removed from the stand-offs without bending the board.
- Pinch the head of each stand-off so that the board is not locked but is still attached to the stand-off.
- Remove the board by gently and evenly pulling the board from all stand-offs at the same time.
Bypass Static Switch Snubber Board Installation
- Position the board in the cabinet over the four white stand-offs that are connected to the left panel.
- Push the board, gently and evenly, onto all the stand-offs simultaneously. Make sure all stand-offs are locked in place.
- Plug the wire connectors into the correct connectors on the board. Check the labels on each connector for proper placement.
Bypass Static Switch Thyristors
There are three thyristors (5) located on the static switch assembly, one for phase A, phase B, and phase C. The thyristors allow for rapid changeover when changing between bypass and online states.
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| Illustration 7 | g03686089 |
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(5) Thyristors
(25) Thyristor mounting screws | |
- Refer to Systems Operation, Test and Adjust, UENR4695, "Internal Component Pre-Removal Steps". Perform the internal component pre-removal procedure to shut down the system and to gain access to internal components.
- Remove the leads that are connected between the thyristor and the static switch driver board.
- Remove the bypass static switch driver board.
- Remove bypass static switch driver board mounting frame by removing four screws connecting mount to the SIO frame.
- Remove the lower 3/4 inch bolt that connects the thyristor to the bus. Remove the THY 9-1 cable and THY 9-1 lead.
- Remove the upper 3/4 inch bolt that connects the thyristor to the bus. Remove the THY 9-3 lead.
- Remove the 3/4 inch bolt that is in the center and connects the thyristor to the bus.
- Remove the four screws (25) that connect the thyristor to the SIO cabinet frame.
- Install the four screws (25) that attach the thyristor to the SIO cabinet frame.
- Install the center 3/4 inch bolt that attaches the thyristor to the bus.
- Install the bottom 3/4 inch bolt that attaches the thyristor to the bus. Connect the THY 9-1 cable and the THY 9-1 lead.
- Install top 3/4 inch bolt connecting thyristor to bus work and THY 9-3 lead.
- Install the bypass static switch driver board mounting frame to the SIO frame with four screws that were removed earlier.
- Install the bypass static switch driver board.
- Install the leads from the thyristor to the bypass static switch driver board.