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WINDING
CONTACT SPRINGS
MOVABLE CONTACTS
Min. (open) Position
FIRST STEP
CONTACT
POSITION
ROTOR
INSULATED
FILLER
FIGURE F.17 – OUTPUT CONTROL UNIT
DEAD SHORT, 1ST STEP, AND OPEN REACTOR TESTS (continued)
PROCEDURE
1. If possible, bring the machine to normal tempera-
ture by connecting a load bank and operating the
machine at 100% output (400 amps @ 36 volts) for
about 30 minutes.
2. Remove the load; turn the Job Selector Rheostat to
MAXIMUM, and the Current Control to MINIMUM
(Contacts on the insulated steel filler or “Open
Reactor”).
3. Short the output terminals and check that the
machine output is 135 to 165 Amps, at 0.2 to 4 Volts
DC*.
If there is no output at the Min. setting of the output
control, there is probably an open circuit in the Series
coils or the conductors connecting them. See the
Internal generator diagram, and the wiring diagram
.
A high output when the reactor is set to Min. would indi-
cate a possible short in the series coils. See the inter-
nal generator diagram.
4. Begin rotating the output control until the output cur-
rent changes, this is the first step or first turn of the
reactor coil. See Figure F.17. The output should
measure 200 to 300 Amps, at 0.2 to 4 Volts DC*.
A slightly high reading in the Min. position, with no clear
first step jump in output could indicate that the contacts
are badly worn, and the contact fingers, rather than the
contacts themselves, may be making contact with the
output control winding. Perform the Output Control
Unit Inspection and Service Procedure.
No change in the output as the output control is slowly
increased to the first step would indicate an open
Output Control Unit, or an open in the cables connect-
ing to it. See the wiring diagram, and perform the
Output Control Unit Inspection and Service
Procedure.
* These values will be accurate if machine is operating
at normal temperature. If the machine is cold, the val-
ues will be higher.
TROUBLESHOOTING AND REPAIR
F-54 F-54
SAE-400 SEVERE DUTY
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