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6. Check electrical calibration per Section 3.2.
3.7.5.4. Counterweight Adjustment Procedure
The values for vane torque given in Table 3-1 refer to the counterweight torque needed
to just balance the vane so that the front contacts just barely close when the relay is in
the normal mounted position without current in the windings and the case is tapped
lightly. Unless the adjustment of the counterweight nut or the heel contact springs has
been changed, or the operating values are not met, this check will not ordinarily have to
be made. In general, it is permissible for the torque to be more than the value shown,
provided the operating values are correct.
1. Attach the "adjustable torque arm" (Figure 3-5) onto the vane shaft of the relay
with the opening of the slot at the bottom, as shown.
2. Hold the "adjustable torque arm" in place by turning the arm, which is threaded
on the end, until it is tight against the vane shaft.
3. Move the small weight that is attached to the "adjustable torque arm" to give the
desired counterweight as specified in Table 3-1.
4. Adjust the counterweight nuts on the relay so that the front contacts will just
make, with the "adjustable torque arm" in a horizontal position. This can be easily
determined by tapping the relay case lightly.
The notches on the arm are spaced to provide the counterweights ordinarily
used. With the small weight in the notch nearest the vane shaft a counterweight
of 100 inch-grains is indicated; in the second notch 125 inch-grains; in further 25
inch-grain steps to 300 inch-grains and 50 inch-grain steps to 600 inch-grains,
except an extra notch at 375 inch-grains.
5. Adjust the counterweight nuts on the vane so that a torque as specified in Table
3-1 is required to just close the front contacts. This torque should be measured
with the relay in its normal operating position and with all operating arms
connected to the heel contacts, using an adjustable torque arm. At least 1/16"
clearance should exist between the end of the counterweight screw and the main
support casting.
Copyright 2019
Figure 3-5. Table Torque Arm
SM 4574F, Rev. 4, March 2019
PV-250 Track Relay
3-16
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