FREQUENCY METER, 0-400 Hz
Figure 8-12. Underfrequency Relay Test Set-Up
(c) Check capacitor Cl between points 5 and
6 on terminal board TB106. Capacitance should be 60
(d) Replace components found to be defective.
(4b) Test the total resistance of rheostat (R28).
Total resistance should be 15,000 ohms + 10%. Test
resistance between wiper arm and eitherend of
rheostat. Resistance should vary between 0 and
(5) Make a point-to-point check of all wiring
and chassis mounted components.
c. Special Relay Assembly.
(1) Check all components for signs of physical
(2) To test the crank relay (K3), apply 24-28
Vdc across the two small terminals and check for
continuity across the two large terminals.
(3) See figure 8-12 and connect the under-
frequency relay (Kl2) (Mode II Sets) as shown.
Test as follows:
ME 6115-545-34/8-12 C1
(a) Adjust the frequency to 400 Hz and the
input votage to 120 volts. Relay contacts should
pick up; lamp DSl should light and DS2 should
(b) Lower frequency slowly until relay con-
tacts drop-out (lights transfer). Contacts should
drop out at 370 + 5 Hz.
(c) Raise frequency slowly until contacts
pick up. DSl should light and DS2 should extinguish.
Contacts should pick up at 370 to 395 Hz.
(d) Raise voltage to 132 volts and check
drop out (lights transfer). Drop out should occur
within ± 1 cycle of drop out at 120 volts.
(4) To test the undervoltage relay (Kll),
(Mode XI) connect the relay in a test circuit as illus-
trated in figure 8-13, and proceed as follows:
(a) Adjust ac power supply to 120 volts,
400 Hz. Lamp DSl should extinguish and DS 2
(b) Reduce voltage slowly to 104 volts and
hold for 2 minutes. Lamp DS1 and DS2 shall main-
8-18 Change 1