Right, Corey.
All critical loads and their wiring aside, the GT only inverter cannot
put out more
current than the pass through relay in the BB inverter is rated for.
For example, you would not want to use a 100 kW PV-GT only inverter
on the AC output of a 4 kW BB inverter.
When grid is up, the GT only inverter is in parallel with the grid just like
it would be if it were not going through the pass through relay except that
the relay in the BB inverter AC current and voltage ratings must be payed
attention to.
boB
On 7/31/2013 11:24 AM, Corey Shalanski wrote:
Mac,
We have installed about ten AC coupled Magnum systems over the past year.
Overcharge protection is accomplished by frequency shift, but Magnum
recommends an auxiliary form of battery management. The cheapest way
to do this is to program the relay driver on the Magnum advanced
remote control (ARC) to open/close a solid state relay at specified
battery voltage setpoints - similar to what Kelly mentioned.
Unfortunately the "cheapest way" sometimes comes back to haunt us in
the form of unanticipated extra costs. We had two customer callbacks
indicating their inverter had mysteriously shut down - site visit
revealed a fried relay in each case.. so I would recommend at least
investing in a good quality relay if you choose this route.
One other thing we have learned is that not all grid interactive
inverters are compatible with the Magnum inverters. Specifically Power
One Aurora string inverters cannot seem to synchronize in off-grid
mode - we have had to switch out Auroras on two projects because of
this. We have had no such synchronization issues with SMA inverters so
far.
--
Corey Shalanski
Joule Energy
New Orleans, LA
On Wed, Jul 31, 2013 Mac Lewis <maclew...@gmail.com
<mailto:maclew...@gmail.com>> wrote:
Here is a paper on AC coupling the magnum.
http://www.wholesalesolar.com/pdf.folder/inverter%20pdf%20folder/MagnumACcoupling.pdf
The key is to connect the AC input terminals on the Magnum to the main
panel (or a panel closer to the utility feed) and then feed the
utility
interactive inverter to a subpanel that is connected to the AC output
terminals on the Magnum. Under normal operation, the Magnum
passes the
power through and the utility interactive inverter is connected to the
grid. If the grid goes down, the internal relays isolate the
Magnum and
the critical load panel from the grid and the Magnum starts to
make a sine
wave that the UI inverter will export power to.
You have to keep the critical load panel amperage below the pass
through
rating on the internal relays on the Magnum, and the grid connected
inverter needs to have a lower output than the Magnum (I think by
10%).
Also, I'm not sure if the diversion controller Magnum has been
working on
is out yet or not.
I've never done this, but I am about to. Any wrenches have experience
doing an AC coupled magnum?
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