tween the moving contact and the moving contact
i. The main breaker (AK-3-50) has a power sensor
support. If there is no opening, it indicates that the parts
overcurrent trip device. When malfunctioning of the
of the contact support that bears on the cam or the cam
power sensor trip is indicated notify direct support
itself has become worn. Sometimes it is possible to
secure a temporary repair by bending the moving
j. Racking in a Circuit Breaker.
contact so it has a smaller separation from the fixed
(1) Push the breaker into the compartment until
contact when in the open position.
the "test" position stop engages to prevent further travel.
(view C fig. 3-10)
3-18. Potential and Current Transformers
(2) Depress the test stop (view D) lever and
push circuit breaker back into compartment until the
Transformers need no care other than keeping them
racking pins on the housing butt against the outer
clean and dry and connections tight.
surface of the racking cam.
(3) Raise the racking handle (view E) this
stroke tip causes racking pin (view A) on housing to
engage the trip interlock link and pin assembly, rotating
the link (view A) and causing the pin (view A) to remove
a. General. There are two circuits fused; the
upward against the adjusting screw on the interlock trip
potential transformer circuit with three 6 amp, 600 volt
paddle. This trips the breaker and holds it tripfree
cartridge fuses and the 115 volt circuit serving the
during the entire racking operation.
heaters, lights and an outlet. This circuit has one 20
(4) Push racking handle down and repeat this
amp fuse. Both fuse blocks are mounted on the inside
four more times (5 complete). The fifth and final stroke
of the right rear door near the top. Always replace blown
releases the trip interlock and allows breaker to be
fuses with the recommended fuse ratings.
b. Replacement of potential transformer fuses (2.
3-16. Meters (Voltmeter and Ammeters)
Fuse block is a molded black totally
(2) Using handle pull the fuse block from the
If the meters have broken cover glasses, damaged
cases or pointers or are not operating, they must be
(3) Replace the blown fuses (6 amp 600 volt).
replaced . Report to organizational maintenance.
(4) Push fuse block back into case.
c. Replacement of 115 volt circuit fuse (3, fig. 2-
(1) Fuse block is an expose cartridge clip for
a. Remove the cover of the switch by loosening the
captive screw on the back.
(2) Replace blown fuse (only one in circuit).
b. Inspect for burning of the contacts, broken shunts
on the moving contacts and for contact wipe.
c.. If the shunts are broken or the contacts badly
pitted, the switch should be replaced.
d. Contacts have sufficient wipe as long as there is
Check that heaters are secured tight and the
an appreciable opening, with the contact, be-
connections are tight.
Section VIII. MAINTENANCE OF ACCESSORIES
3-2 1. General
Instructions contained in this section are for operators
a. Inspect the post for straightness, scratches and
information and guidance in maintenance of the
digs. Clean and repaint where needed.
b. Inspect the chain for breaks and that the snap
hooks are working.
3-22. Storage Cabinets
3-24. Lifting Slings
a. The external and internal surfaces should be
inspected regularly. If they show signs of
a. Inspect each sling for bad kinks or bends, broken
weathering, scratches, digs or are dirty, the surfaces
strands, hook and eye splices are intact.
should be cleaned and repainted where needed.
b. If there are defects in the slings they should be
b. The hinged top should work smoothly and close
properly. If it or the hinges are bent and cannot be
corrected by the operator, he should report this for