Operation Manual – ITW GSE 7400 Battery Powered GPU
90 kVA
Setup Lock / Output Mode / Compensation
Document No. 575.410DB Page 86 of 195
7.6 400 Hz EF Interlock
The EF interlock is a personnel and equipment safety feature that is found in all commercial aircraft.
This 28 VDC signal will not be present until the SSFC closes its output contactor and provides 400 Hz
power to the aircraft. The aircraft will evaluate the 400 Hz power and, if it is within the aircraft’s
tolerance limits, it will then close a relay in the aircraft to provide a 28 VDC signal to the “F” pin / wire in
the power connector plug/cable.
Some load banks do not provide this EF interlock, so the EF interlock function in the unit must be
bypassed. Do not set this value to Bypassed for normal operation with aircraft. This setting must only
be used by qualified personnel for testing the SSFC unit, or when the unit will be providing power to
equipment outside of an aircraft.
Note
The value will be automatically reset to Active if the unit detects 28 volts on the "F" pin input of the
I/O board.
Enter the Setup menu, and then scroll up or down to the EF Interlock submenu. Press the center ●
button to enter the submenu, and then press the ● button again to allow the value to be changed.
Press the up or down arrow buttons to change the selection. Press the center ● button to record the
new value. Press the LEFT arrow button to exit the submenu and return to the submenu list.
7.7 EF Interlock Ripple Level
The EF Interlock Ripple Level is part of the Neutral Voltage Displacement circuit. If an aircraft has a
large unbalanced load and the aircraft power cable has a broken neutral, then it is possible for the
aircraft frame to be energized to a dangerous level. This condition will result in an AC voltage added to
the EF DC signal.
This submenu sets the tripping level for the AC ripple on the DC EF interlock signal. The default value
is 20.0 V and a setting of 0.0 V disables the function.
Enter the Setup menu, and then scroll up or down to the EF Interlock Ripple Level submenu. Press the
center ● button to enter the submenu, and then press the ● button again to allow the value to be
changed. Press the up or down arrow buttons to change the selection. Press the center ● button to
record the new value. Press the LEFT arrow button to exit the submenu and return to the submenu list.
7.8 EF Interlock Delay
Some of the newer aircraft take a longer time between the 400 Hz power being supplied to the aircraft
and the aircraft returning the 28 VDC EF Interlock signal. This setting allows the adjustment of the
amount of time the unit will wait until determining that there is no EF signal and the output power is
shut off. The default value is 3.5 seconds.
Enter the Setup menu, and then scroll up or down to the EF Interlock Delay submenu. Press the center
● button to enter the submenu, and then press the ● button again to allow the value to be changed.
Press the up or down arrow buttons to change the selection. Press the center ● button to record the
new value. Press the left arrow button to exit the submenu and return to the submenu list.
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