Installation Manual

Page 42
© 2015 Sensata Technologies
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 confi rm that the parallel-
stacked units are operating correctly. 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 router (MA, SL1, SL2, and SL3) to each inverter’s Stack
Port (red label).
• Remote cables are connected from the router (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 confi 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 DC Power-up Procedure
Before applying DC power, ensure:
• 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. 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 first powered-up
to synchronize the units for parallel stacking.
4.4.2 Verifying Parallel-stacked Communication
When using MS-PAE series inverters in a parallel-stacked system, you must connect the stack
cables to the router and to each inverter’s Stack port before starting the functional test, applying
DC power, or turning on any inverter. Once DC power is applied—and before turning on any
inverter—press the router’s Port button, and then confi rm that each port with an inverter connected
to it is properly identifying itself (i.e., the top line of the router display correctly identifi es the unit
as a master or slave inverter). Refer to Figure 4-4 to view the appropriate router Port displays
(master, slaves) for the displayed system.
CAUTION: If there is a communication issue, the router’s top line will show the
inverter’s status (e.g., Off, Inverting, Searching) rather than identifying that port’s
connected inverter as a master or slave unit. In that case, the router mistakes the unit
as a standalone inverter, will not sync properly, and may result in damage to that unit—
possibly causing damage to the other inverters in the system as well.