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41-251.21C
ments at regular maintenance periods, the instruc-
tions in Section 6.1, ("Acceptance Check") should be
followed.
All contacts should be cleaned periodically. 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.
6.1
ACCEPTANCE CHECK
The following check is recommended to insure that
the relay is in proper working order.
a. Timer Unit (T)
The directional unit contacts must be in the
closed position when checking the operation of
the timer unit.
b. Contact
By turning the time dial, move the moving con-
tacts until they deflect the stationary contact to a
position where the stationary contact is resting
against its backstop. The index mark located on
the movement frame should coincide with the "0"
mark on the time dial.
For relays identified with a " T ", located at lower
left of stationary contact block, the index mark on
the movement frame will coincide with the "0"
mark on the time dial when the stationary contact
has moved through approximately one-half of its
normal deflection. Therefore, with the stationary
contact resting against the backstop, the index
mark is offset to the right of the "0" mark by
approximately .020". The placement of the vari-
ous time dial positions in the line with the index
mark will give operating times as shown on the
respective time-voltage curves.
c. Minimum Operate Voltage
Set the time dial to position 6. Alternately apply
54% of rated voltage plus 3% and minus 3%.
The moving contact should leave the backstop at
plus 3% and should return to the backstop at
minus 3%.
4
d. Time Curve
Figure 2 (page 8)shows the time curve for the
CRN-1 relay. With the time dial set to the indi-
cated position, apply the voltages specified and
measure the operating time of the relay. The
operating times should equal those of figure 2,
plus or minus 5%.
6.1.1
Indicating Contactor Switch (ICS)
Close the main relay contacts and pass sufficient dc
current through the trip circuit to close the contacts of
the ICS. This value of current should not be greater
than the particular ICS nameplate rating. The indica-
tor target should drop freely.
Repeat above except pass 85% of ICS nameplate
rating current. Contacts should not pickup and target
should not drop.
6.1.2
Directional Unit (D)
a. Contact Gap
The gap between the stationary contact and
moving contact with the relay in a de-energized
position should be approximately .020".
b. Sensitivity
The respective directional units should trip with
value of energization and phase angle relation-
ships as indicated in Table 1. The pickup may be
Table 1:
DIRECTIONAL UNIT SENSITIVITY
Relay Type
Ratings
Values for Min. Pick-up
Volts
Volts
CRN-1
120, 208, 240
Rated
Rated
*
The energization quantities are input quantities at the
relay terminals.
†
Maximum torque angle.
increased to 0.5 amp or higher by increasing the
spring tension.
6.2
ROUTINE MAINTENANCE
All relays should be inspected periodically and the
time of operation should be checked at least once
Type CRN-1
Reverse Power Relay
Phase Angle
*
Relationship
Amperes
.020
†
I leading V by 30°
.023
I In-phase with V
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