3. If the voltage at terminals
and 2 is normal and the contactor CB2
Exercise extreme care when
will not clo se, measure the voltage from
making tests as high voltages
terminal 3 of K12 to TB2-1. The voltage
present will cause injury to
should read 20-32 VDC when the contactor
personnel upon contact.
switch S3 is placed in the closed position.
Measure the voltage from terminal 4 of
b. With switches S1 and S2 open, ener-
K12 to TB2-1. The voltage should read
20-32 V DC with the contactor switch in the
output to 120 VAC, 400 hertz. Close switch
closed position. If no voltage is present,
S1 then S2. Indicator DS1 should energize
K12 relay is defective. The under fre-
and DS2 should de-energize.
is below 370 5 Hz.
c. Lower frequency of variable frequency
supply until indicator DS1 de-energizes and
tag, then disconnect wiring to the under-
DS2 energizes. This should occur at 370
frequency relay. Remove the four screw
assemblies securing the relay in position.
d. If the underfrequency relay does not
6-108. BENCH TEST.
meet the requirements of the above tests
replace the relay.
a. Connect the underfrequency relay to
the test equipment as illustrated in figure
e. Remove the underfrequency relay
from the test equipment.
Figure 6-28. 400 hertz underfrequency relay (K12) test setup
6-84 Change 7