Page 32
©
2017 Sensata Technologies
Operation
3.2 Standby
Mode
The MS-PAE Series uses an automatic transfer relay and an internal battery charger when operating
in Standby mode. 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, the 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 Figure 3-2 to see the
fl
ow of power from the AC
input to the DC and AC output while in Standby mode.
Figure 3-2, Power Flow – Standby Mode
3.2.1 Battery Charging
The MS-PAE 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 Charge
mode begins. After Charge mode begins, the DC voltage is monitored to determine the charging
stage. If the DC voltage is low (
≤
25.6/24-volt models or
≤
51.2/48-volt models), the charger
begins Bulk Charging. If the DC voltage is high (>25.6/24-volt models or >51.2/48-volt models),
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 stages 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
overcharging. The EQ stage (requires a remote control to enable Equalization charge) can be used
to stir up strati
fi
ed electrolyte and to reverse battery plate sulfation that may have occurred—if
recommended by your battery manufacturer.
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
CB1 (30A)
AC HOT 2 IN
AC HOT 1 IN
AC HOT 2 OUT
AC HOT 1 OUT
DC POSITIVE
DC NEGATIVE
AC Transfer Relay
Power Transformer
FET Bridge
CB2 (30A)
AC NEUTRAL
AC NEUTRAL
AC
DC
AC
OUT
240
VAC
120
VAC
120
VAC
240
VAC
120
VAC
120
VAC
DC
OUT
AC
IN
Relay 2
Relay 3
