Installation Manual

Page 38
© 2015 Sensata Technologies
Operation
3.2 Standby Mode
The ME Series features 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, 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 Figure 3-2 to see the fl ow of power from the AC
input to the DC and AC output while in Standby mode.
240
VAC
12
0
VA
C
120
VAC
AC
OUT
Neutral-Ground
Transfer Relay
AC Hot
Transfer Relay
AC HOT 1 IN
AC HOT 2 IN
CB3 (30A)
AC NEUTRAL IN
AC GROUND
Power Transformer
FET Bridge
AC
DC
DC
OUT
AC HOT 1 OUT
AC HOT 2 OUT
CB2
(optional)
CB1
(optional)
DC POSITIVE
DC NEGATIVE
AC NEUTRAL OUT
240
VAC
120
VAC
120
VAC
AC
IN
Figure 3-2, Power Flow – Standby Mode
3.3 Battery Charging
The ME Series is equipped with a PFC (Power Factor Corrected) and PI (Proportional-Integral) multi-
stage battery charger. The PFC feature controls the amount of power used to charge the batteries
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 wave shape to mirror the voltage wave
shape). The PI feature allows the charger voltage and current to change independently. These two
features maximize the real power available from the AC power source (i.e., utility or generator),
which translates into less power wasted and increased charging capabilities.
When an AC source is connected to the AC input, the inverter begins monitoring for acceptable AC
voltage. Once the AC voltage is accepted, the AC transfer relay closes and Charge mode begins.
After Charge mode begins, the inverter’s battery voltage is monitored to determine the charging
stage. If battery voltage is low (≤12.8 VDC), the charger begins bulk charging. If battery voltage is
high (>12.8 VDC), the charger skips the Bulk and Absorb charge stages and goes directly to fl oat
charging. However, if the incoming AC power is lost but returns within 2 minutes the charge mode
returns to the charge stage it was in prior to losing AC input—regardless of the battery voltage.
The multi-stage charger in the ME Series 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 (see Figure 3-3)—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) can be used to stir up stratifi ed electrolyte and to reverse any battery plate sulfation that
may have occurred—if recommended by your battery’s 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
falls below 90 VAC—the charger will stop charging to help stabilize the incoming AC voltage.