53Product description
If the second derating is ineffective (in case of external conditions which are not com-
patible with the safe operation of the equipment) the equipment switches off.
In this case, if the temperature decreases, the power is raised again proportionally.
If it decreases by 20°C the derating feature is exited and full power is restored. After 3
failed attempts, the control logic locks the equipment (alarm “011”).
Thermal Management on Dummy Load
If the temperature measured in the vicinity of the Dummy Load exceeds 90°C, a first le-
vel of derating intervenes slightly in order to reduce the temperature through an output
power reduction.
The power reduction is the lowest possible that allows a thermal balance to be reached
at a temperature of less than 90 °C.
The output power reduction never exceeds 40% with this first derating. In other words.
the output power is always 60% higher than that set by the user, and the “- 3 dB”
signaling does not intervene.
This first derating level is effective in virtually all cases.
If the first level derating is insufficient (extremely rare), a second level intervenes,
further reducing the power, thus obtaining a thermal balance status which is compatible
with the safe operation of the equipment even if it is below - 3dB (with subsequent
corresponding alarm).
If the second derating is ineffective (in case of external conditions which are not com-
patible with the safe operation of the equipment) the equipment switches off.
Thermal derating has a 10°C hysteresis before it attempts to restore the normal opera-
ting conditions of the equipment.
After 3 failed attempts, the control logic locks the equipment.
Current management on the power supply unit (Lifextender) ®
It is provided on amplifiers and exciters.
This is activated when the maximum current for continuous operation of the power
supply is exceeded.
This value is set below the deliverable current limit and constitutes the threshold which
can be exceeded only for short periods (maximum 1 minute at a time). If this situa-
tion arises, the “PSU current derating” function is activated (alarm “013” and/or “014”
relative to amplifiers and modulators) and the ALC management algorithm, envisaged
for normal operating conditions, is replaced by another one wherein the VDS control
and Bias is determined by the power set and, with even higher priority, by the current
delivered by the power supply.
The current derating condition is deactivated when the power delivered returns to the
value set by the user and if the maximum current delivered by the power supply is less
than or equal to the maximum value allowed for continuous operation.
Thermal management on the power supply unit (Lifextender) ®
It is provided on amplifiers and exciters.
The power supply management algorithm according to the temperature is the same as
that on the RF unit, and it is logically connected in “OR” to the latter.
The first Derating level (acting directly on the output power) is activated when the po-
wer supply temperature exceeds 75°C, while the second level is activated - if the first is
ineffective - if the temperature does not stabilize below this value.
In the latter case, the output power is brought below – 3 dB with the same procedure
as that described for the RF section.
The activation of this feature is shown on the display as alarm “015” and /or”016” rela-
tive to amplifiers and modulators.
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