54 Product description
Fault management on RF modules (Lifextender) ®
It is provided on amplifiers and exciters.
This manages the maximum deliverable power according to the number of RF amplifier
modules considered to be operating correctly.
If one or more MOSFETs are considered faulty (this happens when the absorbed current
is 10% below the average value), the RF output power is reduced to the expected value
when a fault occurs.
The failure case report and the relative maximum power achievable is described in a
complex table obtained through tests. It is designed to stop failure propagation and
prevent excessive stress on the MOSFETs that still work due to the ALC feature (which
would require them to deliver all the missing output power).
In order to prevent a ridiculously high number of alarm SMSs, no messages are sent
during this phase: the alarm SMS, if validated, is only sent after the adaptation procedu-
re of the output power according to the table parameters and only if the -3dB condition
occurs on the output power.
The activation of this feature is shown on the display as alarms “008” and “009” relati-
ve to amplifiers and modulators.
Cooling Management on the fan unit (Lifextender) ®
According to the actual cooling requirements, the rotation speed of the fans is adjusted
from a minimum of 60% to a maximum of 120% approx. (these values may vary accor-
ding to the models of fan used).
The cooling requirement is estimated based on the accurate temperature measure-
ments which are performed in correspondence with the RF MOSFETs and the power
supply unit in the case of amplifiers and modulators and on the Dummy Load.
The Cooling Management aims to extend the effective lifetime of the fans, minimize
the quantity of dust that may be transported by the air flow and allow the safe opera-
tion of the equipment also under extreme temperature conditions.
Without the Lifextender the fans always work at 100%.
2.9.2 Hardware protections
The hardware protection system comprises:
• fast electronic and fuse protection of power supplies;
• fast electronic protection on the fan power supply;
• fast protection against excess reflected power (SWR/VSWR) following a strong load
mismatch. This protection is activated when the reflected power value exceeds 10%
of the forward power;
• protection against splitter and combiner overheating through fans with a thermo-
stat;
• designed based on redundancy so as to eliminate the “SINGLE-POINT-FAILURE”, that
is any points which alone define an OFF-AIR situation;
• construction of metal parts in stainless steel and aluminium, treatment of the elec-
tronic boards with protective paint (tropicalization), closing off the most sensitive
components to air flow with special shields in order to provide protection against
corrosion.
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