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SECTION 4 | Parameter Setup
When EVO™ is operating in Inverting Mode (there is no AC input), its output frequency will be equal to the frequency
that has been selected by the programming parameter “DEFAULT FREQ” (TABLE 4.6 and Section 4.5.2.1). When AC
input is made available, it is rst monitored for 2 sec. If it is within the programmed values of (i) frequency limits (TABLE
4.6), (ii) low voltage limits (TABLE 4.7) and (iii) high voltage limits (TABLE 4.8), synchronization process is initiated to
synchronize the frequency and phase of the Inverter Section with the incoming AC input voltage. Details are given
below:
a) Parameter “SYNCHRONIZATION” set at Option “0= Fine”
This is the “Default Setting” for EVO-1212F/1212F-HW/1224F/1224F-HW. This setting is applicable
when Grid / Inverter Generator is connected to AC Input. Synchronization control logic used in this
option is suitable for more stable frequency output of Grid / Inverter Generator. Under this option,
the frequency and phase of the Inverter Section are synchronized with the Grid as follows:
i. First, the frequency of the Inverter Section is tracked in steps of 0.1Hz per cycle and made
equal to the frequency of the Grid / Inverter Generator input.
ii. Then, the phase of the Inverter voltage relative to the Grid voltage is tracked by 1º per cycle.
When the phase of the Inverter voltage is within ± 3.5º of the input voltage waveform, the
Transfer Relay is activated to transfer the AC load from the Grid / Inverter Generator to the
Inverter Section at zero crossing of the voltage waveform.
b) Parameter “SYNCHRONIZATION” set at Option 1= Coarse
This setting is selected for EVO-1212F/1212F-HW/1224F/1224F-HW if a Generator is connected
to AC Input. As compared to very stable frequency of Grid / Inverter Generator, the frequency of
a Generator may vary considerably depending upon the performance of its Speed Governor that
compensates for the drop in RPM / frequency when electrical load is switched on / increased or,
rise in RPM / frequency when electrical load is decreased /switched off. Hence, if synchronization
sensitivity set is at “0= Fine” as in Section 4.5.2.8 (a) above, it may take very long for the Inverter
Section to synchronize with the Generator or, may not synchronize at all. Under this option, the
frequency and phase of the Inverter Section are synchronized with the Generator differently as
follows:
i. First, the frequency of the Inverter Section is NOT tracked at 0.1Hz per cycle as in Option “0=
Fine” [See Section 4.5.2.8(a) above] but is made equal to the Generator frequency at zero
crossing of the Inverter voltage.
ii. Then, the phase of the Inverter voltage relative to the phase of the Generator / Inverter
Generator voltage is tracked by 1º per cycle. When the phase of the Inverter Section is within
± 10.5º of the Generator input voltage waveform, the Transfer Relay is activated to transfer
the AC load from the Generator to the Inverter Section at zero crossing of the voltage
waveform.
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