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Figure 2-9. Unit pole opening
TM-5-6120-250-34 Substation Trailer Mounted 500 KVA AC 4160-416Y/240V 208Y/120V 3 Phase 50/60 Hertz Avionics Model 950-2200A Manual
Connecting Load Break Switch
(6)  Auxiliary blade release.
The auxiliary
misalignment of contacts.  Do not bump
blade release hook (14, fig. 2-5) should be adjusted to
switch during installation or it may crack or
hold the blade out of the arc chute until a predetermined
break the insulating barriers.
position in the closing operation. Close the switch slowly
(5)  Lift and place switch in cabinet on the
with the maintenance handle and note the position of the
mounting angles.
primary blades when the auxiliary blade is released by the
Line holes of switch base with holes of
hook (10, fig.  2-9).  The hook should be adjusted by
mounting angles.
setting the camming screw (8) to release the auxiliary
(7)  Insert up through the front hole in the left
blade within the range of 1/2 inch before arcing contacts
side mounting angle a bolt, lockwasher and a plain
touch. After adjustment is made the lock nut (9) should
washer, and thread it hand tight into switch base.
be tightened.
(8)  Insert a bolt with lockwasher and plain
(7)  Primary contact pressure.  The primary
washer up through front hole in right side mounting angle,
place the spacer on top of angle pushing bolt through it
finger pressure has been adjusted at the factory to be 12
and into the tapped hole of switch base. Tighten hand
pounds per contact. This can be measured. with a pull
scale exerting a pressure against the contact surface.
(9)  Insert two bolts and plain washers up
The contact pressure of each finger 15, fig. 2-5) should
through left mounting, one midway, other in rear. Then
be measured  individually. Increase or decrease the
place lockwasher and nut on them, tighten hand tight.
contact pressure by loosening or tightening the contact
(10) Install rear right side bolts same manner
bolts (4).
as Step (8).
(8)  Arcing finger contact pressure. The arcing
(11) Check switch position for flatness and
finger contact pressure should be 12 pounds.  This
alignment, close upper front panel to make sure operating
pressure can again be measured with a spring scale
handle can be inserted and used to operate switch. If
against the contact surface. Loosen or tighten the contact
switch is not at proper height, raise mounting angle to
bolts (7, fig. 2-8) as necessary.
next hole up in cabinet side or spacer may have to be
(9)  Primary blade hinge pressure. The correct
hinge pressure is essential for proper operation of the
switch.  The hinge pressure is difficult to measure.  A
required torque to move the primary blades can be easily
If spacers are used in mounting switch,
measured and substituted. The break away torque of the
make sure switch is mounted flat and is
hinge (the torque required to start the blades moving)
not  distorted.  If  it is  twisted  and
should be between 60 to 90 inch-pounds. This can be
distorted it will not operate because of
measured by pulling at the buffer stop or spacer (1, fig. 2-
6) on the primary blade. Use a spring scale without the
(12) When  switch is mounted  in correct
primary contacts, arcing contacts and auxiliary block
position and flat, tighten all five mounting bolts. See table
contacts engaged. The scale reading should be 51/2 to
1-1 for correct torque values.
81/a pounds. If adjustment is necessary, remove cotter
(13) Fasten the ends of the narrow insulating
pin from either side of hinge pin (16, fig. 2- 5 1. Tighten
barrier across the bottom front of switch to the mounting
or loosen the nut as required. Move the nut in increments
of one sixth of a turn. This assures line-up for the cotter
d.  Test. A standard 60 cycle high potential test at
pin replacement in hole and slot in the nut.
14,000 volts RMS will normally indicate whether the
c.  Mounting Load Break Switch.
device is satisfactory for service.
(1)  Open upper and lower hinged front panels
of high voltage section.
Before applying a high-potential test make
(2)  Remove upper and lower rear panels.
certain that the switch is disconnected
(3)  Remove horizontal barriers and hardware
from the source and load.
that fit around primary connectors of switch.
(1)  With  the switch contacts in the fully
(4)  Inspect switch mounting angles in cabinet
opened position, apply the high potential to each terminal
for level from front to rear and from one side to the other.
individually for one minute with all the other terminals and
When mountings are level and square make sure they are
the frame grounded.
(2)  After high potential tests are made all
organic insulating material should be inspected for visible
Switch must be mounted in the housing,
leakage current paths. Necessary action must be taken to
supported at both front and rear.  Care
replace insulation that may have been affected by
must be taken not to distort the frame by
moisture absorption.
mounting on unflat or out of square

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