Exciter Rotor Voltage Test Procedure - Lincoln Electric Classic 300 MP Service Manual

LINCOLN ELECTRIC

EXCITER ROTOR VOLTAGE TEST PROCEDURE

Service and repair should be performed by only Lincoln Electric factory trained personnel. Unauthorized
repairs performed on this equipment may result in danger to the technician or machine operator and will
invalidate your factory warranty. For your safety and to avoid electrical shock, please observe all safety
notes and precautions detailed throughout this manual. If for any reason you do not understand the test
procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department
for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
TEST DESCRIPTION
This procedure will help determine if the Exciter Rotor Winding is operating at normal voltage.
MATERIALS NEEDED
5/16" Nutdriver
Volt/Ohmmeter
Wiring Diagram
TEST PROCEDURE
1. Turn off the engine on the Classic 300 MP machine. The engine should be at normal operating
temperature for this test. If the machine is cold, the voltage readings may be slightly higher than
specified.
2. Using a 5/16" nutdriver, remove the four screws securing the exciter cover to the machine. See
Figure F.22.
3. Using a volt/ohmmeter, connect the probes to the brush terminals. See Figure F.23. See Wiring
Diagram.
4. Start the engine and place the idle switch in the "High" position. Read the voltage at the brush
terminals. The voltage should be approximately 140 VDC*.
5. Set the RUN/STOP switch to "STOP".
If the meter reading is normal, this test is complete.
If the voltage measures zero or very near zero, perform the Exciter Flashing Voltage Test Procedure
and the Exciter Rotor Resistance And Ground Test Procedure.
If voltage is higher than specified, the engine RPM may be too high, or there may be voltage
intrusion from one of the higher voltage stator windings to the stator exciter winding. Perform the
Exciter Stator Short Circuit and Ground Test Procedure.
If the voltage is lower than 140, the engine RPM may be too low or there may be problems in the
windings or other exciter circuit components or connections.
6. Perform the Exciter Field Diode Test Procedure.
7. Check the wiring, fuse and terminals connecting the exciter field diode to the exciter stator winding.
See Wiring Diagram.
8. Reconnect the leads to the AC terminals of the exciter field diode.
Classic® 300 MP Service Manual
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