Magnum Energy AC Load Diversion Controller (ACLD-40) - Manual (Page 30)

Page 23
©
2015 Sensata Technologies
Operation
3.0 Operation
3.1 ACLD Operation
Normally, when utility power is available, the grid-tie inverter in the system converts the renewable
energy to AC that works in parallel with the utility to: power the load panels (main panel and sub-
panel for critical loads) in the home, charge the battery system, and feed any power—from the
renewable energy source—that is not used in the home back into the utility grid.
The utility power connects to the input of the MS-PAE Series inverter/charger,. This causes an
automatic AC transfer relay inside the inverter to close, passing the current from the incoming
utility power through the MS-PAE Series inverter. Some of the current passing thru the MS-PAE
Series inverter is used by a powerful internal battery charger to keep the battery bank charged
in case of a power failure.
Info: The ACLD controller is designed to be connected and powered from the AC output
of a battery-based inverter that provides a MagNet communications port and has an
output of 230 or 240 VAC (50 or 60 Hz). Typically the MS-PAE Series (MS4024PAE or
MS4448PAE) is used, but the MS-E Series and MS-PE Series inverters can also be used
for applications that require 230VAC/50Hz inverters.
The current that passes thru the MS-PAE Series inverter connects and powers the ACLD, and then
passes through the ACLD to the grid-tie inverter. Once power is connected to the ACLD, t he ON/OFF
power switch ( Figure 1-4, Item 8) on the ACLD controller m ust be turned on to begin operating.
T he controller’s green LED blinks slowly (once a second) when the ACLD is on. With utility power
connected and the ACLD turned on, the ACLD will be in the Inactive mode (not actively monitoring/
regulating the battery voltage) because the MS-PAE Series inverter/charger is providing three-
stage (Bulk, Absorption and Float) battery bank charging.
Info: When the MS-PAE Series inverter is fi rst turned on, its automatic Search feature
is enabled. This feature must be disabled for the ACLD to operate correctly. To disable
the Search Watts feature, either connect a load on the inverter’s output that is greater
than 5 watts or use a remote display (ME-RC, ME-ARC or ME-RTR) to turn the Search
Watts setting to “OFF”.
If a utility power outage occurs, the MS-PAE Series inverter comes on and starts powering the
critical loads. However, now that the utility power is no longer connected to the input of the MS-
PAE Series inverter and the inverter is no longer in the charge mode, the ACLD becomes enabled
and enters Standby mode. In Standby mode, the ACLD starts monitoring the battery voltage to
determine when to become “active” and divert power to a diversion load to keep the battery from
overcharging. [During the utility power outage, the grid-tie inverter—after a minimum 5-minute
reconnect time—reconnects to the AC output waveform of the MS-PAE Series inverter and starts
inverting all the energy from the renewable energy source just like it did when it was connected
to utility power.] However, during a utility power interruption, the main panel loads are no longer
connected and any excess power that is generated cannot be sold/exported to the utility grid. This
means there may be more power generated than the critical loads can consume, causing current to
be pushed back into the inverter’s AC output, then to the battery bank, causing the battery voltage
to rise. As the battery voltage rises and the battery becomes fully charged (or the battery voltage
starts to increase above the regulation setpoints), the ACLD exits Standby mode and enters Active
mode. In Active mode, the ACLD uses Pulse Width Modulation (PWM) regulation to control how
much current from the renewable energy source is allowed to fl ow into the diversion load to keep
the battery voltage from rising further. As the battery’s current requirements change, the PWM
switch inside the ACLD either closes for longer periods of time (higher duty cycle) to direct more
current to the diversion load; or closes for shorter periods of time (lower duty cycle) to decrease
the current fl ow to the diversion load, which allows more current to fl ow into the battery.
Once the battery is fully charged, the PWM switch fully closes, causing all the current produced by
the renewable energy source to be diverted to the diversion load. When the current is no longer
required to be diverted away from the battery, the PWM switch fully opens and causes the ACLD to
exit Active mode and return again to Standby mode to start monitoring the battery voltage.