Protections; Reflected Power; Over-Excitation; Ac Mains Line Protection - Hitachi E-Compact Medium Power Series Operation Manual

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 [2000]) 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 will immediately
signal Through the Current Alarm LED, and this will trigger the routine protection against reflected
power. This will gradually decrease 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 disappearance 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 will always occur when the
reflected power is 2% of the nominal power of the EQP. Already the reflected value that will make the
EQP reduce direct power is configurable from 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,
will 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 phase and earth, thus absorbing peak voltage, not allowing it to damage the power supply.
Protection against 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.
E-Compact Medium Power
87 | 106