ABB HU Instruction Leaflet page 17

Figure 16. Test Circuit of the HU and HU-1 Relays
All contacts should be periodically cleaned. A contact
burnisher Style 182A836H01 is recommended for
this purpose. The use of abrasive material for clean-
ing contacts is not recommended, because of the
danger of embedding small particles in the face of
the soft silver and thus impairing the contact.
CALIBRATION (ALL RELAYS)
Use the following procedure for calibrating the relay if
the relay has been taken apart for repairs or the
adjustments disturbed. This procedure should not be
used until it is apparent that the relay is not in proper
working order. All adjustments to be done with
relay inside its case . (See "Performance Check".)
Polar Units
1. Contacts
NOTE: In adjusting either the stationary contact
or backup, the screw in the elongated holes of
the assemblies should
removed, during the adjustment procedure.
a. Upper Unit (HRU) - Place a 0.065 to 0.070
inch feeler gage between the right-hand
Sub 2
1477B71
be loosened, not
Figure 17. Variation of Second Harmonic Content of Test
Current
(front view) pole face and the armature. This
gap should be measured near the front of the
right-hand pole face. Bring up the right-hand
(front view) backstop until it just makes with
the moving contact. Tighten the screw in the
elongated hole of the backstop and remove
gage. Place a 0.046 feeler between the mov-
ing contact and the stationary contact on the
left-hand (front view) side of the polar unit.
Bring up the stationary contact until it just
makes with the gage. Tighten mounting
screw in the elongated hole of the stationary
contact and remove gage.
b. Lower Unit (DU) - Place a 0.065 to 0.070
inch feeler gage between the left-hand (front
view) pole face and the armature. This gap
should be measured near the front of the
right-hand pole face. Bring up the left-hand
(front view) backstop until it just makes with
the moving contact. Tighten the screw in the
elongated hole of the backstop and remove
gage. Place a 0.065 to 0.070 feeler gage
between the moving contact and the station-
ary contact and the stationary contact on the
41-347.12C
Sub 1
471047
17