Hobart 6921 Series Operation And Maintenance Manual page 116

OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
Protective Circuit (Continued)
Trouble, Symptom & Condition
Load contactor opens during
power delivery. Indicating light
ON
Generator
Trouble, Symptom & Condition
1. No (or low) voltage output.
2. Generator operates single
phase.
3. Generator overheats.
Chapter 3-1
Page 24
Test or Inspection
a. One of the resistors (R26,
R27 or R28) across
overload transformer is
open Circuited.
b. Overload device printed
circuit board defective.
Test or Inspection
a. Shorted diode in exciter
rectifier (CR2).
b. Open or shorted exciter
rotor winding (G2).
c. Open or shorted exciter
field windings (L2).
d. Open or shorted generator
rotor windings (L1).
a. An open or short circuited
winding in generator stator
(G1).
a. Loose connection causing
high resistance.
b. Improper or blocked
ventilation.
c. Check Stator windings
short circuited.
Corrective Action
An open resistor will cause a
higher than normal Voltage.
Check Resistors (Sect. 1-1; 1,
Fig. 13). Replace if defective.
With unit off, measure
resistance between terminals B
and E, Fig. 8. If zero ohms
resistance is measured, replace
Overload device (K4)(Section
1-1; 7, Fig. 11).
Corrective Action
Check diodes in accordance
with sect. 2-3, Para. 6 If diodes
are good, proceed to step B.
Use ohmmeter to check for
open or shorted condition. If
rotor windings are good,
proceed to step C.
Check for field resistance. See
Sect. 2-3. Fig. 14 for normal
values.
Check resistance with
ohmmeter to determine if open
or short circuited.
Check stator winding
resistances. See Sect. 2-3, Fig.
12 for normal values.
Check all output connections for
looseness. Look for
discoloration caused by heat.
Tighten or replace as required.
Check for foreign materials
(rags, etc.) blocking air flow.
Provide adequate ventilation.
Check Stator windings. See
Sect. 2-3, Fig 12.
February 28/94 Revised