Hobart 9OC24S Operation Manual page 56

OPERATION, MAINTENANCE, AND OVERHAUL MANUAL, TM-240A
SELF-PROPELLED GENERATOR SET, SPEC. NO. 5381A
A solid-state overload signaling device (Ref. Fig. 10, item 8) is also
connected to the protective monitor module and performs a function
similar to the sensing relays.
Trip values for the sensing relays and overload devices are as follows:
Overvoltage relay trips at 130 V to 134 V.
t
Undervoltage relay trips at 93 V to 103 V.
Overfrequency relay trips at 415 Hz to 425 Hz.
Underfrequency relay trips at 390 Hz to 395 Hz.
Overload device trips at any value over 125% rated load capacity.
See Section l-l, Para. 5, E , (9), (d) f or more specific and detailed infor-
mation regarding overload device.
(b) Protective monitor module
The protective monitor (1) is a new, solid-state device with a hermetically-
sealed, reed-type, relay. The solid-state, printed circuit board, or "card"
replaces five latching relays and a time delay relay which were formerly
used. In place of latching relays, SCRs (silicone-controlled rectifiers) are
used; one each for overfrequency, underfrequency, overvoltage, under-
voltage, and overload. The board includes five memory circuits and a
5-second time delay circuit. Each memory circuit is connected to a
corresponding sensing device (overload module, overvoltage relay, etc.).
All of the circuits are connected to the module relay coil, and any one of
the circuits can energize the coil to open the relay contacts. Thus, when
a sensing device energizes any one of the module circuits, the module relay
is also energized to break the load contactor holding circuit and allow the
load contactor to open. All circuits, except the undervoltage circuit,
function immediately to open the load contactor. A time delay system is
designed into the undervoltage circuit to prevent nuisance opening of the
contactor under conditions of momentary undervoltage. in the generator
output. An undervoltage condition which continues uninterrupted for a
period of 4 to 12 seconds (depending upon adjustment) will cause the time
delay circuit to open the load contactor. Each of the five circuits is
connected to a corresponding indicating light (8, 10, 12, 13, and 15)
which is turned on when a fault occurs.
The module relay will remain energized (OPEN) and the light will remain
ON until the reset switch (Ref. Fig. 7, item 9) is pushed to break the
module 24-V DC circuit, and allow the relay to return to normal,
CLOSED position.
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