UPS 120, UPS 150, UPS 250, UPS 300, UPS 301, UPS 500, UPS 600, UPS 750 and UPS 900 Uninterruptible Power Supplies Caterpillar

Illustration 1	g01269681
(1) Zig Zag ControllerBoard

Description

The Zig Zag Controller board (ZZC) (1) is present only in 4-wire applications.

The board (1) is mounted on the left panel. The board (1) is required in order to establish the neutral point of the 3-phase output when the system is in discharge mode and the system is disconnected from the utility input.

The board (1) provides the stand-alone control for the proper switching of the neutral power conductor during entrance and exit of discharge.

During normal operation, the output Zig Zag Transformer (1) is not connected to the utility neutral. When an outage is detected, the ZZC will switch the neutral of the Zig Zag Transformer (1) to the utility neutral for the duration of the discharge.

The board contains voltage and current ports that are used to detect a failure of the Zig Zag Transformer (1). If a need for discharge is detected, the ZZC (1) will turn on the gates of the Silicon Controlled Rectifier (SCR). In addition, the ZZC (1) will close an output in order to close the neutral contactor.

Removal Procedure

Refer to Systems Operation, Testing and Adjusting, RENR9988, "Internal Component Preremoval Steps (SMS Bypass Cabinet)" in order to shut down the system and gain access to internal components.

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Illustration 2	g01269700
Diagram of the Zig Zag Controller Board

1. Disconnect all connectors. Verify each label for each connector for subsequent installation. Refer to Illustration 2.

2. Remove the ground screw from the corner of the board (1).

3. Disconnect the white plastic standoffs that connect the board (1) to the left panel.

   Note: The Zig Zag Controller board (1) must be removed from the standoffs without bending the board.

4. Compress the head of each standoff so that the board (1) is not locked, but the board is still attached to the standoff.

5. Remove the board (1) from all standoffs at the same time.

Installation Procedure

1. Position the board (1) in the cabinet over the white standoffs that are connected to the left panel. Install the board (1). Verify that all the standoffs are locked into the correct position.

2. Insert the ground screw in the board. Tighten the ground screw into the left panel.

3. Connect the wire connectors. Verify the labeling of each connector for proper placement. Refer to Illustration 2.