ABB HU Instruction Leaflet page 13

the relay is in proper working order. All checks can
best be performed by connecting the relay per the
test circuit of figure 16. RELAY MUST BE TESTED
IN CASE.
1. Minimum Trip Current
NOTE: The moving contact of the upper polar
unit (HRU) closes to the left-hand (front view) sta-
tionary contact. The moving contact of the lower
polar unit (DU) closes to the right-hand (front
view) stationary contact.
With SPDT switch open and SPST switch closed
and relay set on 5-ampere tap, apply 1.35 to 1.65
amperes for the 30% sensitivity relay and 1.6 to
1.9 amperes for the 35% sensitivity relay. Relay
should operate. The upper polar unit may operate
for lower currents, but not below 1.0 ampere. This
low pickup will not impair its operation on magne-
tizing inrush currents and should not be dis-
turbed if it is found to be less than the lower polar
unit. If the pickup value is considered to be too
low, it should be checked after applying a polariz-
ing current magnitude of 20 times tap value to
relay terminals 3 and 7. This will cause the upper
polar unit to pickup at a current of approximately
1.65 amperes.
Figure 15. Example for Setting Calculations
2. Indicating Instantaneous Trip Pickup
3. Indicating Contactor Switch
With switch open and relay set on 5 ampere tap,
apply 50 amperes to relay. Indicating instanta-
neous trip should pick up and its target should
drop freely.
The contact gap should be approximately 0.094
inches between the bridging moving contact and
the adjustable stationary contacts. The bridging
moving contact should touch both stationary
contacts simultaneously.
Block the polar unit contacts closed and pass
sufficient dc current through the trip circuit to
close the contacts of the ICS. This value of cur-
rent should not be greater than the particular ICS
nameplate rating. The indicator target should
drop freely.
Repeat above except for 85% of the ICS name-
plate rating current. Contacts should not pickup
and target should not drop.
41-347.12C
Sub 2
289B412
13