©
2009 Magnum Energy Inc
Page 40
Operation
3.2 Standby
Mode
The MS Series features an automatic transfer relay and an internal battery charger when operating
in the Standby Mode. The Standby Mode begins whenever AC Power (Utility or Generator) is
connected to the inverter’s AC input. Once the AC voltage and frequency of the incoming AC power
is within the AC input limits, an automatic AC transfer relay is activated. This transfer relay passes
the incoming AC power through the inverter to power the AC loads on the inverter’s output. This
incoming power is also used to activate a powerful internal battery charger to keep the battery
bank charged in case of a power failure. Refer to
fi
gure 3-2 to see the
fl
ow of power from the AC
input to the DC and AC output while in the Standby Mode.
240
V A C
120
V A C
120
V A C
A C
O U T
N eutral -G round
Trans fer R elay
A C H ot
Trans fer R elay
A C H O T 1 IN
A C H O T 2 IN
C B3 (3 0 A )
A C N E U TR A L IN
A C G R O U N D
P ow er Trans form er
FE T B ridge
A C
D C
D C
O U T
A C H O T 1 O U T
A C H O T 2 O U T
C B2
(optional )
C B1
(optional )
D C P O S ITIV E
D C N E G A TIV E
A C N E U TR A L O U T
240
V A C
120
V A C
120
V A C
A C
IN
Figure 3-2, Power Flow - Standby Mode
3.3 Battery
Charging
Magnum Energy’s MS Series is equipped with an active PFC (Power Factor Corrected) and PI
(Proportional-Integral) multistage battery charger. The PFC feature is used to control the amount
of power used to charge the batteries in order to obtain a power factor as close as possible to 1
(or unity). This causes the battery charger to look like a resistor to the line (forces the charge
current waveshape to mirror the voltage waveshape). The PI feature allows the charger voltage
and current to change independently. These two features maximize the real power available from
either utility or generator AC power sources, which translates into less power wasted and greater
charging capabilities than most chargers available today.
When an AC source is connected to the AC input, the inverter begins monitoring for acceptable AC
voltage. Once the inverter has accepted this AC voltage, the AC transfer relay closes and the Charge
Mode begins. After Charge Mode begins, the DC voltage is monitored to determine the charging
stage. If the DC voltage is low (
≤
12.8 VDC/12 volt models or
≤
25.6 VDC/24-volt models), the
charger begins Bulk Charging. If the DC voltage is high (> 12.8 VDC/12 volt models or >25.6 VDC/
24-volt), the charger will skip the Bulk and Absorb charging stages and go directly to Float Charging.
The multistage charger can use up to
fi
ve different charging stages to help monitor and keep the
batteries healthy; The
fi
ve stage include an automatic 4-stage charging process: Bulk, Absorb,
Float and Full Charge; and a manual Equalization (EQ) charge stage. The automatic 4-stage charge
process provides complete recharging and monitoring of the batteries without damage due to over
charging. The EQ stage (requires the ME-RC remote to enable Equalization charge) is used to stir
up strati
fi
ed electrolyte and try and reverse battery plate sulfation that may have occurred.
While charging, the unit may go into Charger Back-off protection, which automatically reduces the
charge current to the batteries. This is caused by: 1) The internal temperature is too hot - the
charger automatically reduces the charge rate to maintain temperature; or 2) The AC input voltage
falls below 90 VAC - the charger will stop charging to help stabilize the incoming AC voltage.
