Hobart 9OC24S Operation Manual page 64

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HOBART BROTHERS COMPANY
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OPERATION, MAINTENANCE, AND OVERHAUL MANUAL, TM-240A
SELF-PROPELLED GENERATOR SET, SPEC. NO. 5381A
The overload module is equipped with a hermetically-sealed, reed-type
relay, the contacts of which are normally open. The solid-state circuitry
is designed to close the relay contacts when the output current in ANY
phase reaches 125% of normal, rated value. The closed relay sends a
signal to the protective monitor. This signal "gates" the overload SCR
(silicone-controlled rectifier) in the protective monitor and interrupts
the load contactor holding circuit, allowing the load contactor to open.
The following is a list of overload module characteristics:
NOTE: The overload protective system will function when any phase
carries 123% to 127% of rated load.
At 125% load the device will function in 4 minutes.
At 150% load the device will function in 16 seconds.
At 200% load the device will function in 4 seconds.
NOTE: All times are plus or minus 25% and are nonadjustable.
(e) Rectifier
A diode-bridge rectifier (5) receives 400 Hz AC from phase C of the gen-
erator output and converts it to a pulsating, direct current for energization
of the load contactor holding coil only. This DC coil-holding circuit is
controlled indirectly by controlling the 400 Hz AC to the rectifier. The
ground circuit for the rectifier's AC supply must pass through ihe relay 'I
contacts in the protective monitor module to ground cable N . Therefore,
any time a protective device functions to open the protective monitor
relay, the rectifier's AC circuit is opened. No DC is then available
for the load contactor holding coil, therefore, the load contactor opens.
6. Operating Mode Safety Devices
Until now all safety devices described have been designed to protect the aircraft, genera-
tor, or engine against damage by abnormal conditions of voltage, frequency, heat, oil
pressure , e tc .
The devices described here are designed to prevent operation of the unit until certain
controls are properly positioned, or certain conditions met.
A. Drive Mode Safety Device
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