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TM 5-4120-287-15
c.
Control Relays. The control relays are as follows: trip relays K101; time delay relay K102; temperature control
relay K103; and line contactor relays K104, K105, K106 and K107.
WARNING
Set master circuit breaker to OFF position and disconnect power supply from power input receptacle
(J101) when testing the relays
(1) Trip Relay (K101)
(a) Connect the positive side of a 28 vdc power supply to rectifier (CR1) terminal C; and connect the negative
side to transformer (T1) terminal 6.
(b) Press system reset switch.
(c) Using a multimeter, check for continuity across K101 terminals 5 and 3, and 2 and 11.
(d) If terminal 5 and 3, and 2 and 11, are open, trip relay K101 is defective and must be replaced.
(e) Using a jumper, momentarily connect K101 terminal 7 and 1; then remove jumper.
(f)
Check K101 terminals 5 and 3, and 2 and 11 for an open circuit.
(g) If terminals 5 and 3, and/or 2 and 11 exhibit continuity, trip relay K101 is defective and must be replaced.
(h) Press system reset switch. Terminals 5 and 3, and 2 and 11 should now exhibit continuity; if not, either
trip relay K101 or system reset switch S1 is defective and must be replaced.
(i)
Set master circuit breaker to OFF position.
(j)
Connect to K101 terminals 1 and 7, and test for continuity.
(k) Press system reset switch S1; if multimeter shows continuity while S1 is depressed then switch S1 is
defective and must be replaced.
(l)
If multimeter indicates switch S1 opens when depressed, then trip relay K101 is defective and must be
replaced.
(2) Time delay relay (K102).
(a) Connect multimeter test leads to relay K102 terminals 5 and 7.
(b) Apply 28 vdc across relay K102 terminals 2 and 3.
(c) Observe that after 2.25 seconds have elapsed and before 3.75 seconds have elapsed, multimeter reads
28 vdc
(d) If multimeter reading is not obtained within specified time range, then time delay K102 is defective and
must be replaced.
(e) Check for an open condition across K103 terminals 1 and 7.
(f)
If K103 terminals 1 and 7 exhibit continuity either relay K103 or capacitor C2 is defective and must be
replaced.
1.
Check capacitor C2 for shorted condition.
2.
Replace capacitor C2 if defective (shorted).
3.
Replace relay K103 if capacitor C2 is not shorted.
(g) Disconnect jumper T (fig. 1-9) from K103 terminal 8; then apply 28 vdc across relay K103 terminals 4 and
8.
(h) Check that K103 terminals 5 and 3 and 1 and 7 exhibit continuity.
(i)
If continuity is not exhibited, relay K103 is defective and must be replaced.
(j)
Check for an open condition across K103 terminals 2 and 5.
(k) If relay K103 terminals 2 and 5 exhibit continuity, relay K103 is defective and must be replaced.
(l)
Check for an open condition across K103 terminals 1 and 6.
(m) If K103 terminals 1 and 6 exhibit continuity either relay K103 or capacitor C3 is defective and must be
replaced.
1.
Check capacitor C3 for shorted condition.
2.
Replace capacitor C3 if defective (shorted).
3.
Replace relay K103 if capacitor C3 is not shorted.
6-7
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