GUARD ASSEM. (L.H.) 6P7868 - Caterpillar

Illustration 1 g01445763
PMPE Generator Wiring Diagram (1) Voltage regulator and/or related components (CR1-CR6) Diodes (CR7) Varistor (L1) Exciter field (stator) (L2) Exciter armature (rotor) (L3) Main field (rotor) (L4) Main armature (stator) (L5) Pilot exciter armature (PM) Permanent magnet (RFA) Rotating field assembly (CST) Customer supplied transformer
Table 1
Tools Needed    
Part Number     Part (1)     Quantity    
6V-7070     Digital Multimeter     1    
146-4080     Digital Multimeter (RS232)     1    
( 1 ) Only one multimeter is necessary for this test. Either of the multimeters that are shown will work.
The high voltage that is produced by an operating generator set can cause severe injury or death. Before performing any maintenance or repairs, ensure that the generator will not start.Place the engine control switch in the "OFF" position. Attach "DO NOT OPERATE" tags to all starting controls. Disconnect the batteries or disable the starting system. Lock out all switchgear and automatic transfer switches that are associated with the generator.
Measure the resistance of the following windings: (L1), (L2), (L3), (L4) and (L5). The winding that is being tested must be disconnected from the other components before the resistance can be measured. The following resistance measurements are approximations. If the measured value is not near the listed approximation, the winding is probably damaged. For a more precise resistance value, consult the Technical Marketing Information (TMI). Refer to the generator arrangement that is in question.Note: The winding temperature affects the resistance. When the winding temperature increases, the winding resistance also increases. When the winding temperature decreases, the winding resistance also decreases. Therefore, a correct measurement can be performed only when the winding is at room temperature.The following armature windings have little resistance: (L2), (L4) and (L5). The resistance of these windings will measure near 0 ohms. Use a milliohmmeter to measure the resistance of the armature windings.Exciter Armature (Rotor) (L2) - less than 0.1 ohmMain armature (Stator) (L4) - less than 0.1 ohmPilot Exciter Armature (L5) - less than 0.1 ohmUse a multimeter in order to measure the resistance of field windings (L1) and (L3) .Exciter Field (Stator) (L1) - approximately 3.0 ohms to 6.0 ohmsMain Field (Rotor) (L3) - approximately 0.75 ohms to 2.0 ohmsNote: There should be no continuity between any winding and ground. There should be no continuity between any winding and another winding.