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SECTION 8 |
widely, the G4 Series has a narrower window of + 5 Hz and – 3 Hz to
allow transfer / bypass of the utility power to the load and carry out
battery charging. If a generator is used as the AC input power source
and the G4 is set in "Utility Mode" and if the frequency variation of the
generator is more than + 5 Hz / - 3 Hz, the G4 will not transfer / bypass
the generator output to the load / charge the batteries.
When "Generator Mode" is selected, the frequency and phase of
the AC output of the inverter are synchronized with the output
frequency and phase of the generator but the value of frequency
is not considered for transfer purposes. The inverter remains
synchronized with the generator frequency at all times and the
load also sees the actual frequency of the generator at
all times.
Automatic Interruption of battery Charger
Current In Generator Mode When Generator
Frequency is outside the Range of 45 Hz
to 65Hz
Please refer to detailed information under "Principle of Operation" in
Section 4, page 14 under heading "Automatic Reduction in Battery
Charger Current in Generator Mode When Generator Frequency is
Outside the Range of 45 Hz to 65 Hz.""
In G4 Series, protection is provided to limit generator voltage distortion
to acceptable limits. When the batteries are being charged at higher
charging current, the generator has to deliver proportionately higher
current that produces higher frequency deviation and waveform
distortion in the output waveform of the generator that may lead to
high voltage transients, spurious zero crossings, errors in frequency
determination and loss of synchronization. When the frequency of
the generator is outside the range of 45 Hz to 65 Hz, the control logic
will stop charging to reduce distortion. The Display Screens "Battery
Charging" (SCREEN 4, page 52) and "Charging Mode" (SCREEN 6, page
52) will show message "Inp Hz Abnormal". Also, Display Screen showing
Internal (Int) and External (Ext) charging Amps (SCREEN 5, page 52) will
display OA against Internal (Int) charger.
The charging will be resumed once the frequency of the generator is
within the window of 45 Hz to 65 Hz.
!
CAUTIon!
As a generator may have wider frequency
fluctuations, these fluctuations will be passed on
to the load. Hence, when a generator is used as a
source of transferred / bypassed AC power, the load
will be forced to operate under wider frequency
fluctuations that will not be controlled and the
user should ensure that when "Generator Mode"
is selected, the loads should be able to tolerate the
frequency variations of the generator.
Operation
!
ATTENTION!
Le générateur pourrait avoir des fluctuations de
hautes fréquences, et ces fluctuations serait passées
à la charge. Ainsi, quand le générateur est utilisé
comme source de puissance CA transferée, la charge
serait obligée de fonctionner avec des fluctuations
de fréquence qui seront pas controlées. Alors
l'utilisateur doit assurer que la mode «Generator
mode» est sélectionnée, et que les charges sont
capables de tolèrer des variations de fréquences
provenant du générateur.
Transfer From Inverter Mode to
Generator Mode & Vice Versa
Whenever the G4 Series is switched ON, it will always start in Inverter
Mode first even if generator or utility input is available. The output of the
inverter ramps up from around 40 vAC to 120 vAC in around 350 ms
under "Soft Start" and is slowly synchronized with the frequency of the
generator and the load is transferred / bypassed to the generator when
fully synchronized and at the same time, the Battery Charger Section
starts charging the batteries in parallel with the external charger, if
connected. This preparation time for ensuring synchronized transfer from
the Inverter Mode to the Generator Mode may take around 20 to 30 sec
(the actual transfer is completed within 20 ms). The transfer from the
Inverter Mode to the Generator Mode will take place only if the voltage
of the generator is within the limits of low and high input voltages set
through the "Setting Mode"(SCREEN 2, page 40 and SCREEN 3, page
41). The value of the frequency is not considered for transfer
purposes.
After the load has been successfully transferred to the generator, the
Inverter Section is kept in standby condition and its output frequency
and phase are kept synchronized with the phase and frequency of
the generator to enable safe and faster transfer to the inverter for un-
interrupted backup power.
If the output of the generator fails or if the voltage of the generator
deviates more than the programmed limits given above, the Transfer
Relay de-energizes and the load is transferred to the inverter within the
rated Transfer Time of 20 ms. After transfer has taken place, the inverter
executes a soft start wherein its voltage is ramped up from around
40 vAC to the full rated voltage in a time span of around 350 ms. This
soft start / ramp up of its output voltage reduces overloading of the
inverter due to reduction in inrush current drawn by the load of the load
as a result of lower startup voltage.
If subsequently, the output voltage of the generator returns to within
the programmed limits, the load is once again transferred back to the
generator as explained above.
noTe: Loss of power for around 20 ms during transfer will show up as a
slight flicker in incandescent lamps because the filament of incandescent
lamp does not cool down immediately in such a short duration. However,
a Compact Fluorescent Lamp (CFL) will switch off (its Holdup time is
SAMLEX AMERICA INC. | 51
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