©
2017 Sensata Technologies
Page 43
Parallel Operation
4.4
Functional Test for Parallel-stacked MS-PAE Inverters
Paralleled inverters must communicate together in order to provide 120/240 VAC to the loads.
They will shut down if any inverter faults occur. The functional test will con
fi
rm that the parallel-
stacked units are operating correctly.
CAUTION:
To prevent damage when using MS-PAE series inverters in a parallel-stacked
system, you must connect the stack cables to the ME-RTR and to each inverter’s Stack
port before applying any power, or turning on any inverter.
Before performing the functional test, ensure the following:
• All DC disconnects to the inverters are turned off.
• All AC input and output circuit breakers are turned off.
• Stack cables are connected from the ME-RTR (MA, SL1, SL2, and SL3) to each inverter’s
Stack Port (red label).
• Remote cables are connected from the ME-RTR (P1-P4) to each inverter’s Remote Port
(blue label).
Info:
Coordinate the remote cables to the router’s communications ports so that
the Master inverter is connected to Port 1, Slave 1 inverter is connected to Port 2,
etc. (remote and stack cables are connected to the inverters in order from left to
right). This con
fi
guration makes it easy to keep track of which inverter is displayed
on each port, and allows you to easily identify the master and slave units.
• Only the same inverter models are stacked together (i.e., all MS4024PAE models, or all
MS4448PAE models).
• The NEUT OUT of all inverters are connected to the same neutral bus.
• DC and AC grounds are connected and properly installed.
• AC input and output connections are wired correctly to the terminal block, and are not
reversed (double-check before turning on the inverters).
4.4.1 Power-up Procedure (Stacked System)
Before powering up the stacked system, ensure:
• No AC power is connected
• All DC connections are properly connected and tight.
• Battery voltage is within the DC voltage range for your parallel-stacked inverters
(i.e., 24-volt battery bank for a 24-volt inverter).
• The DC negatives of each inverter are connected together.
• The positive (+) battery cables are connected to the positive (+) battery terminals through
a DC disconnect and overcurrent device.
• The negative (–) battery cables are connected to the negative (–) battery terminals.
Apply battery power to all the inverters by closing the DC circuit-breakers to each inverter at the
same time (see CAUTION below). The inverters remain OFF, but the green status indicator on the
front of each inverter quickly blinks once to indicate that DC power has been connected and the
inverters are ready to be turned on.
CAUTION:
It is crucial that the DC voltage be connected to all the inverters within 5
seconds of each other. The units go through an autodetect when
fi
rst powered-up to
synchronize the units for parallel stacking.
4.4.2 Verifying Parallel-stacked Communication
Once DC power is applied—and before turning on any inverter—press the router’s Port button,
and then con
fi
rm that each port with an inverter connected to it is properly identifying itself
(i.e., the top line of the router display correctly identi
fi
es the unit as a master or slave inverter).
Refer to Figure 4-5 to view the appropriate router Port displays (master, slaves) for the displayed
system.
