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Metal Oxide Varistor MOV Surge Protector Description

Illustration 1	g01274915
Location of the metal oxide varistor (MOV) surge protectors (1) Lower MOV Surge protector (2) Upper MOV Surge protector

Illustration 2	g01274927
Wiring for the MOV surge protector

The metal oxide varistor (MOV) surge protector (1) is located on the back panel at the bottom of the MMS System cabinet. In the post 2.4 hardware, the System cabinet has another MOV (2). The MOV (2) is connected to the ceiling of the System cabinet. Refer to Illustration 1 for the locations.

The MOV surge protector is connected to the 3-phase input power from the multiple module units. The MOV surge protector monitors the incoming voltage for spikes. When a spike is detected, resistance in the MOV is overcome and the extra voltage is diverted ground.

There are three LEDs on the front of each MOV. There is one LED for each phase in order to indicate proper operation of the MOV.

Note: If the MOV surge protector fails, do not restart the machine. Call technical support for further assistance.

Removal Procedure for the Lower MOV

Refer to Systems Operation, Testing and Adjusting, RENR9988, "Internal Component Pre-removal Steps (MMS System Cabinet)" in order to shut down the system and gain access to internal components.

1. Disconnect the wires that lead from the back of the MOV surge protector (1). There are three black wires. The wires have a labeling to the location of the wire. Verify the labeling of the wire for subsequent installation.

2. Remove the four bolts that secure the surge protector bracket to the rear of the cabinet.

3. Remove the nut that attaches the MOV (1) to the bracket.

4. Remove the MOV (1) from the bracket.

Installation Procedure for the Lower MOV

1. Place the wires that come from the back of the MOV (1) through the bracket.

2. Place the large nut onto the wires.

3. Install the nut onto the threaded portion of the MOV (1).

4. Attach the MOV bracket to the back of the cabinet with the four bolts. Refer to Illustration 1. Tighten the bolts to 11.5 N·m (100 lb in).

5. Connect the wires that come from the back of the MOV (1) to the cabinet. Refer to Illustration 2 for wiring connections.

Removal Procedure for the Upper MOV

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

1. Disconnect the wires that lead from the back of the MOV surge protector (2). There are three black wires. The wires have a labeling to the location of the wire. Verify the labeling of the wire for subsequent installation.

2. Remove the nut that attaches the MOV (2) to the bracket.

3. Remove the MOV (2) from the bracket.

Installation Procedure for the Upper MOV

1. Place the wires that come from the back of the MOV (2) through the bracket.

2. Place the large nut onto the wires.

3. Install the nut onto the threaded portion of the MOV (2).

4. Connect the wires that come from the back of the MOV (2) to the cabinet. Refer to Illustration 2 for wiring connections.