Digital Acoustics ESBx-110 Dokumentacja Pobierz pdf (Strona 329)

100

101

Maintenance and Troubleshooting

ADDvantage-32 PLUS ● AC to DC Power Converter

7-31

IF THE SNUBBER IS NOT DISCONNECTED, THE VOLTAGE

DIFFERENCE MAY BE VERY SMALL.

Leaky SCRs on older style drives may require burden resistors. There are RESISTOR

MODIFICATION KITS which are used as a burden on systems that have leaky SCRs.

The resistors are standard now on newer drives, but on older drives may need to be

added.

There are two different kits, the only differences being in the lugs provided. The resistors

are 25K ohms, 50W and are connected across the armature circuit. The resistors bleed

off SCR leakage so that false tach loss trips do not occur on the application of a run.

KIT P/N INSTRUCTIONS FOR USE ON

A22481 A22428 280, 360, and 510 Amp DC Drives

A22374 A22375 Most others. Check with factory.

7.7 INDIVIDUAL SCR MODULE TEST

An SCR module can be tested individually when removed from the drive. It is

recommended that the SCR module be cold for this test and should not have been in

operation for a considerable time preceding the test. Follow the steps below for each

SCR on the module.

USING AN ANALOG OHMMETER SET TO MEGOHM SCALE

1. Measure the resistance between the Cathode and Anode. It should be 1MΩ

or greater.

2. Reverse ohmmeter leads. It should again read 1MΩ or greater.

3. Connect positive lead of the ohmmeter to anode and negative lead to

cathode. Jumper anode to gate. The resistance should now read less than

1KΩ.

4. Removing the jumper should indicate a reading of 1MΩ or greater on the

ohmmeter.

Any variation of readings on the ohmmeter indicates a leaky, shorted, or open SCR.

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