Hitachi EC702MP-BB3, Operation Manual

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E-Compact MP-BB3 Series
5. Protections
5.1. Reflected Power
If the incidence of reflected power at the transmitter due to any external or internal factor occurs, refer to
the measurement screen (MEASUREMENTS) by browsing the software’s navigation Menu, according to
instructions given in the Operation Section of the Digital Control System.
If the value of the reflected power exceeds the value of 2% of rated power, the control immediately
signals through the Current Alarm LED and this triggers the routine protection against reflected power.
This gradually decreases the value of the forward power until the amount of power reflected returns to
less than 2% of rated output. At this time, the software returns to gradually increase the value of forward
power, foreseeing the possible absence of the reflected power. Thus, the equipment will be oscillating
between increase and decrease of the direct power around the power value that provides a reflected
power of 2% of rated power, always seeking the return to the rated power of equipment.
The 2% value to generate the reflected power alarm is fixed, ie. the alarm always occurs when the
reflected power is 2% of the nominal power of the EQP. Already the reflected value that makes the EQP
reduce direct power to a configurable 2 to 5%. To change this value, go to Setup Menu-> Alarms Mask->
Reflected and change as needed.
5.2. Over-excitation
If an excessive increase in the value of the excitation signal level occurs, the control, through the ALC,
interact with the exciter, to maintain a constant output power in it’s rated value.
5.3. AC Mains Line Protection
Each piece of equipment has it’s own independent power supply, all of which have equal protection
features.
- Protection against short circuit
- Surge Protection
Basically, the surge protection on the network is performed by inserting the varistors between phases
and between the phase and ground, thus absorbing peak voltage and not allowing it to damage the
power supply. Protection against the short-circuit is carried out by monitoring the current in the output of
the power supply. If the current exceeds a pre-set reference value, it will understand that the source
output is shorted and should be disabled through the shutdown pin.