Diode Test; Testing The Transformer-Rectifier - Hobart 60CU24 Operation And Maintenance Manual With Illustrated Parts List

OM-2098C / Operation and Maintenance Manual
60CU24 / Series 500060C / 400 Hz. Generator Set
Test Connection
Generator Stator Phase A to N (G1)*
Generator Stator Phase B to N (G1)*
Generator Stator Phase C to N (G1)*
Exciter Stator Field (L2)
A - B, B - C, C - A Exciter Armature (G2)
Generator Revolving Field (L1)
*NOTE: The two leads of a phase must be connected when test is made. Take readings when unit
is cold and in an ambient temperature of 70 ºF (21ºC.).

5) Diode Test

Test values for diodes are not given here because they could be misleading. Test values may vary even
between diodes of the same part number, rating, and manufacturer. General instructions for testing
diodes are as follows:
a) Disconnect exciter windings from diode lead(s).
b) Use a good quality ohmmeter. An instrument, which indicates 50 ohms at the center of the scale, is
preferable.
NOTE: Make certain the battery is in good condition and the pointer is adjusted to zero when the test
lead points are shorted together.
c) Hold one ohmmeter lead point on the threaded end of the diode. Hold the other lead point on the
wire terminal end. Observe and note the indicated resistance. Now reverse the lead connection on
the diode. Again observe and note the ohmmeter indicated resistance. Generally speaking, if an
infinite or very high resistance was indicated with the leads connected one way and a low, readable
resistance was indicated with the leads connected the opposite way, the diode may be considered
good.
6) Testing the Transformer-Rectifier (Optional, See Appendix A)
The 28.5 VDC transformer-rectifier is an optional add-on to the GPU. See Appendix A for more details on
the adjustment and test of the transformer-rectifier.
April 01, 2005
Generator and Exciter Test Readings
Figure 10
Resistance (Ohms)
0.00235
0.00235
0.00235
26.5
0.1
2.1
Chapter 2-3
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