Permanent Magnet Hold-Down Force; Polarity) - Hitachi PN-150BE Manual

PN-150BE Biased High Efficiency Vital Relay
4.5.5.3. Adjusting the Back Contact Springs
Using the Test No. 3 values per Table 4-1, hold a gauge of the proper value firmly at the
back stop pin by energizing the relay in the reverse direction, adjust the back contact
springs so that light is just barely visible between the contact tips. Check that Test No. 4
allows the contact to close. Again remove the operating arm and determine that the heel
contacts have at least 0.005" opening at the front and back contacts as per test 5c,
Table 4-1.
If the operating arm is bumped while adjusting either the front or back contacts,
deenergize the relay and position the operating arm by working the armature by hand a
few times before proceeding.
A check must be made that when the front contacts are just touching, the back contacts
have at least 0.020" opening as per Test 5a, Table 4-1.
When the armature is in the fully released position, the front contacts must have at least
0.050" opening as per. Test 5b, Table 4-1.
If any of the screws holding the contact springs into the contact block have been
loosened or removed, when replacing them they must be tightened only with a torque
screw driver set at
5-inch pounds maximum. Further tightening may crack the bakelite contact block. After
tightening these screws, they should be sealed with Minnesota Mining Cement #821, or
equivalent applied from the outside of the block allowing the cement to penetrate down
alongside the contact fingers into the contact block.

4.5.6. Permanent Magnet Hold-Down Force

With the relay in the normal upright position and deenergized, a force measured with
gage N105440 of at least 45 grams (90 grams for special "UT" timing unit relay, see
Table 4-1, Test 12) applied on the end of the bottom horizontal contact engaging pin of
the operating arm should be required to cause the armature to move away from the
permanent magnet. This check should be made before and after the relay has been
calibrated and after energizing with the charge value using normal polarity of
energization.
Because of the allowable variations the stiffness of the material from which the contact
springs are made, the hold-down force may vary between relays that have the same
strength magnets. For this reason then, on relays where hold-down is too high (using
nominal spacers) replace one of the phosphor bronze screws (shiny nickel plating) that
holds the magnet assembly to the pole piece with a steel screw (dull tin plating)
J463078 which will shunt some of the magnetic flux. Bending the adjustable shunt away
from the magnet slightly will raise the hold-down force if necessary (see Figure 4-2).

4.5.7. Polarity)

See Figure 2-3. The polarity should be checked as follows: With the negative power
lead connected to the "+" or "+A" coil terminal, the positive power lead connected to the
-
"-" or " B" coil terminal, and the relay energized at the "charge" value, the armature
-
should not pick up. With the polarity of energization reversed so that the positive power
lead is connected to the "+" or "A" coil terminal and the relay energized at the "charge"
Copyright 2019 SM 4551L, Rev. 0 1, March 2019 4-11