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Troubleshooting
6.9.23 ISO_##_OT, Over-Temperature
There are 3 System Level ISO loads in the Z5 transmitter. These are designated :
• ISO_Az and ISO_Bz - These 2 are the 2.5kW ISO loads located in the middle of
the Isolation Boards. Their component designation is R9 on the Isolation Board
schematic.
• ISO_AB - This one is the ISO (reject) load on the 5kW hybrid which is combin-
ing the outputs of the Z-Planes. It is physically located above the 5kW power
block. The component designation is A2A5R1 on the Overall Wiring Diagram.
All of these loads are monitored for temperature by the Master Controller and both
of the PA controllers simultaneously. The responsibility for system protection
belongs to the Master Controller, with the PA Controllers acting as backup in case
of a Master failure.
6.9.23.1 System ISO Foldback
The Master Controller has a foldback routine it will use to protect these system
components called ISO APC Foldback. ISO APC Foldback uses 2 thresholds,
115°C and 130°C. If one of these 3 loads reaches 130°C the Master Controller will
switch the fan to high speed and start the foldback routine by reducing the APC
voltage at a fixed rate. If the temperature is reduced, the foldback will stop at 115°C.
If the temperature goes below 115°C the foldback will be reversed and the power
will be very slowly increased until the power output is back to normal or until the
load temperature again rises to 115°C at which point the power increase would stop.
If the temperature then rises back up to 130°C the foldback procedure will start all
over. In other words, the Master Controller is going to try and keep the load
temperature between 115°C and 130°C at some maximum power output. It is
important to note that no faults will be reported in the fault log for a foldback, only
the foldback indication while the overtemperature condition is present.
NOTE:
All PA and ISO temperature faults are based on actual thermistor tempera-
tures and/or a predicted value of temperature based on the rate of rise in tem-
perature over a given period of time. Therefore, a resistor temperature which
is predicted to reach 130°C will cause an overload the same as an actual read-
ing. Due to the prediction, it is possible to get over-temperature faults even
though the actual temperature reading is not above the threshold.
6.9.23.2 System ISO Overload (Fault)
If the System ISO APC Foldback routine fails to reduce the temperature of the
offending ISO load and the temperature reaches 145°C, the Master Controller will
mute the IPAs and the exciter and the PA Controllers will mute the PAs. At this
point an ISO_Load fault will be reported in the fault log and the transmitter will
mute momentarily. The possible faults are:
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