Replacing the Transformer in the Automatic Transfer Switch{4469} Caterpillar

Engines:

3304 (S/N: 02B4226-UP; 5CA1-UP)

3306 (S/N: 70R8891-UP)

3406 (S/N: 90U1-UP)

3408 (S/N: 67U1-11134; 78Z1-1143)

3408B (S/N: 67U11135-16070; 78Z1144-4866)

3408C (S/N: 67U16071-UP; 78Z4867-UP)

3412 (S/N: 38S1-16483; 81Z1-14500)

3412C (S/N: 38S16484-UP; 81Z14501-UP)

3508 (S/N: 23Z1-UP; 70Z1-UP)

3512 (S/N: 24Z1-UP; 67Z1-UP)

3516 (S/N: 25Z1-UP; 73Z1-UP)

D330C (S/N: 02B1-4225)

D333C (S/N: 62M1-UP; 70R1-8890)

Introduction

This Special Instruction contains the procedure for determining and replacing faulty transformers in the automatic transfer switch. The new 184-2461 Transformer Kit consists of four transformers (NT2, NT3, NT4 and ET2) and eight self-tapping machine screws.

Transformers NT2, NT3 and NT4 monitor the line voltages under the normal condition. Transformer ET2 along with adjacently mounted transformers ET3 and ET4 monitor the line voltages under the emergency conditions. If one of transformers NT2, NT3, NT4 or ET2 has failed, the automatic transfer switch will not transfer to the power source monitored by the faulty transformer(s).

Reference: Service Manual, SENR2164, "Transfer Switches".

Determining Faulty Transformer

1. Checking Transformer NT2

   1. Ensure that the transfer switch is set for NORMAL automatic operation.

   2. Follow the black and white leads on transformer NT2 back to their termination points. Check for 120 ACV. If the voltage is present, check for 24 ACV across terminals 1 and 2 on the logic package. Check for 12 ACV across terminals 1 and 3. Check for 12 ACV across terminals 2 and 3 on the logic package. See Illustration 1.

      Expected Result: The voltages are present.

      Results:

      • YES - The voltages are present. Go to 2.

      • NO - Any of these voltages are not present. Transformer NT2 has failed. After checking transformers NT3, NT4 and ET2, proceed to ""Replacing Transformer(s)" ".

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Illustration 1	g00677354
The logic package

2. Checking Transformer NT3

   1. Ensure that the transfer switch is set for NORMAL automatic operation.

   2. Check for 12 ACV across the yellow leads on terminals 4 and 5 on the logic package.

      Expected Result: The voltage is present.

      Results:

      • YES - The voltage is present. Go to 3.

      • NO - The voltage is not present. Transformer NT3 has failed. After checking transformers NT4 and ET2, proceed to ""Replacing Transformer(s)" ".

3. Checking Transformer NT4

   1. Ensure that the transfer switch is set for NORMAL automatic operation.

   2. Check for 12 ACV across the yellow leads on terminals 6 and 7 on the logic package.

      Expected Result: The voltage is present.

      Results:

      • YES - The voltage is present. Go to 4.

      • NO - The voltage is not present. Transformer NT4 has failed. After checking transformer ET2, proceed to ""Replacing Transformer(s)" ".

4. Checking Transformer ET2

   1. Ensure that the transfer switch is set for NORMAL automatic operation.

   2. Check for 24 ACV across terminals 8 and 9 on the logic package. Check for 12 ACV across terminals 8 and 10 on the logic package. Check for 12 ACV across terminals 9 and 10 on the logic package.

      Expected Result: The voltages are present.

      Results:

      • YES - The voltages are present. Therefore, the fault may be intermittent. Check all the electrical connections. If the problem still exists, repeat the entire procedure.

      • NO - Any of these voltages are not present. Transformer ET2 has failed. Go to ""Replacing Transformer(s)" ".

Replacing Transformer(s)

1. Disconnect all power to the automatic transfer switch by locking open the upstream switching devices on both the normal feeder conductors and emergency feeder conductors. The upstream switching device can be a circuit breaker.

2. Remove the voltage selector connector from the transformer panel by depressing the tabs on the side of the connector and pulling away from the transformer panel. See Illustration 2.

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Illustration 2	g00677356
Removing the voltage selector connector

3. Remove the transformer panel from the baseplate by removing the four screws which are located on the sides of the baseplate. See Illustration 3. After removing the last screw, gently tilt the top of the transformer panel forward until all transformers are visible. If wiring is long enough, support the transformer panel on top of logic modules. See Illustration 4. If wiring is not long enough, use some type of spacer between logic modules and the transformer panel. Do NOT support the transformer panel by the wiring.

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Illustration 3	g00677357
Removing transformer panel

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Illustration 4	g00677358
Transformers of the automatic control switch

4. Locate the faulty transformer(s). Remove the faulty transformer(s) from the assembly. It will be necessary to drill out two pop rivets each in order to remove the transformers. See Illustration 5.

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Illustration 5	g00677360
Removing a faulty transformer

5. Disconnect the transformer connections. Those that terminate in a nylon connector may be removed by using a very small screwdriver or probe to compress the "barbs" on the terminal pin inside the connector. See Illustration 6. Alternatively, the AMP extraction tool may be used, by pressing the tool onto the pin until it "bottoms". See Illustration 7. The pins should be carefully removed. Replace the transformer. Fasten the transformer using the included self-tapping screws. Install the screws through the transformer panel into the transformer base.

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Illustration 6	g00682989
Disconnecting transformer connections

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Illustration 7	g00682998
The AMP pin extraction tool

6. Reinstall the transformer leads in the same order as the old leads were removed. Match color codes. For those wires that have AMP pins, gently push the pin into the rear of the nylon connector until the pin is properly seated and locked. See Illustrations 8 and 9. If the red or yellow leads have AMP pins on them and the pins are not needed (for older type switches) the pins may be removed and the wires cut to length, stripped and connected to the logic package terminal strip.

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Illustration 8	g00683005
The nylon connector

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Illustration 9	g00683006
The nylon connector

7. Reinstall the transformer panel with four existing screws. See Illustration 10. Reconnect the voltage connector.

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Illustration 10	g00683008
Reinstalling of the transformer panel

8. Test the automatic transfer switch for proper operation.