SEAL 1788210 - Caterpillar

Self-Excited Regulators (SE) (see Illustration 1)
Mode 1: Failure of any component such that the regulator "sees" a loss of sensing at lead 20 or 24.
Result: Output of the regulator will be shut off and the generator output voltage will be at minimum.
Mode 2: Failure of any component such that the regulator "sees" a loss of sensing at lead 22.
Result: The regulator will go to "full field" resulting in the generator output voltage going to maximum. This will normally result in a fuse failure (opening), turning off the regulator. If the fuse(s) should fail to open, the overvoltage condition will continue for approximately 12 seconds. At this time, the over-excitation limit built into the regulator will turn the regulator off.
If sensing leads 20 or 24 are lost, generator output will be at minimum for the VR4 Voltage Regulator ONLY.
Illustration 1. Self-Excited Regulator (SE). Droop transformer (CT1) and droop rheostat (R1) may or may not be supplied. The exciter field is L1.Permanent Magnet Excited Regulators (PM) (see Illustration 2)
Mode 1: Failure of any component such that the regulator "sees" a loss of sensing at lead 20, 22, or 24.
Result: The regulator will go to "full field" resulting in the generator output voltage going to maximum. This condition will continue for approximately 12 seconds. At this time, the over-excitation limit built into the regulator will turn the regulator off.
Mode 2: Failure of any component such that the regulator "sees" a loss of input from the PM exciter on leads 11, 12, or 13.
Result: If one lead is lost, generator output capability will be reduced. Generator output voltage will drop if capability is exceeded. If two or more leads are lost, generator output voltage will be at minimum.
Illustration 2. Permanent Magnet Excited Regulator (PM). Droop transformer (CT1) and droop rheostat (R1) may or may not be supplied. The exciter field is L1, the stator is L5.