Magnum Hybrid Inverter Question

[dclark1946]

Recently started investigating hybrid inverters since I (retired EE) have been having consulting discussions with an individual who is powering a trailer(in a remote location) off grid with solar/batteries and Champion generator. I have downloaded the user manual for the Magnum MSH3012M hybrid inverter used in this application. The description of this inverter indicates it is capable of augmenting input ac power (generator in this case). Description such as "load support parallels inverter output with input ac power" sounds kinda like paralleling Honda generators but there is a spec for transfer time (16 msec) which sounds more like an UPS that switches from ac input power to internal inverter power when there is an input power interruption. For this individual's application there have been issues with low voltage transients caused by A/C cycling on.

I would like a better understanding of how this inverter operates supplementing input ac input sources.

[jharrell]

dclark1946 wrote:
After reading the explanation and thinking about it some more I still have a question about the transfer switch and what it switches. It sounds like the inverter ac output is normally connected to the ac load side so it can add power if required but if input ac power is lost and the inverter needs to provide all of the load it is already connected to the load so I must not be fully understanding the switch connection. Just asking for a high level switch connection topology.

Please read the excellent manual from Magnum here. It details everything very clearly. The transfer switch is mainly there to prevent backfeed and switch neutral to ground in the case of no shore input.

Here is the switch topology direct from page 30:

[LittleBill]

dclark1946 wrote:
After reading the explanation and thinking about it some more I still have a question about the transfer switch and what it switches. It sounds like the inverter ac output is normally connected to the ac load side so it can add power if required but if input ac power is lost and the inverter needs to provide all of the load it is already connected to the load so I must not be fully understanding the switch connection. Just asking for a high level switch connection topology.

the owner manual gives a pretty solid description of how it works.

what your specifically looking for

"3.4 Transfer Time
While in Standby mode, the AC input is continually monitored. Whenever AC power falls below
the VAC dropout voltage (80 VAC, default setting), the inverter automatically transfers back to
Inverter mode with minimum interruption to your appliances—as long as the inverter is turned
on. The transfer from Standby mode to Inverter mode occurs in approximately 16 milliseconds.
While the MSH3012RV is not designed as a computer UPS system, this transfer time is usually
fast enough to hold them up. However, the VAC dropout setting has an effect on the ability of the
loads to transfer without resetting. The lower this setting, the longer the effective transfer will be
and therefore, the higher the probability for the output loads to reset. This occurs because the
incoming AC voltage is allowed to fall to a level that is so low that when the transfer does occur,
the voltage on the inverter’s output has already fallen low enough to reset the loads.
The disadvantage of a higher VAC dropout setting is that smaller generators (or large generators
with an unstable output) may nuisance transfer. This commonly happens when powering loads that
are larger than the generator can handle—causing the generator’s output voltage to constantly
fall below the inverter’s input VAC dropout threshold"


based on this you might want to adjust the voltage setting higher so it transfers quicker.

Page 47

[Itinerant1]

It's not switching it's load sharing. On the me-arc you set the amount of amp that you want to use from the ac source (generator, power pole). If you're hooked to a plug in source of 15a you set the incoming ac to 15a so any demand above that it will be used from the batteries. Now if your load is 15a or less the inverter will just automatically pass the power through until a larger demand requires extra from the batteries.

[dclark1946]

After reading the explanation and thinking about it some more I still have a question about the transfer switch and what it switches. It sounds like the inverter ac output is normally connected to the ac load side so it can add power if required but if input ac power is lost and the inverter needs to provide all of the load it is already connected to the load so I must not be fully understanding the switch connection. Just asking for a high level switch connection topology.

[dclark1946]

Thanks for the in depth explanations. That is exactly what I was looking for,

[gatorcq]

Agree with Jharrel, as I set mine set at 15 amp shore power, even though I am on 50 amp.

I also used either the VDC or SOC connect, do in part because of my 1600 watts of solar on my Rv.

In the winter months (Oct - Feb) of Arizona, I will get about 50% usable of my panels, since I do not elevate them on the roof.

[jharrell]

I have the 3012. There are two hybrid modes that it chooses automatically, VDC and AAC.

In VDC the inverter detects a secondary charger and pulls the batteries down to float voltage by inverting the extra current. In my rig this works with my solar or alternator.

With AAC there is a setting you manually adjust for your max shore power draw, if your loads exceed that it draws from batteries to make up the rest. Allows you to run say off a 15a outlet and still do short big loads.

When ac power is coming in either generator or grid the transfer switch is engaged, there is no cut over time for the hybrid modes. The inverter is synced to the line frequency and its either pulling power to charge or pushing power to load support all solid state. The 16 msec transfer time is for the transfer switch, if you lose shore (generator shut down) it will transfer and keep going without interruption.

More details can be found in their ARC remote manual, for some reason thats where they document most of the inverter functions rather than the inverter manual.

[KD4UPL]

When not inverting it is charging. When a large load occurs it stops charging and starts inverting. This takes a little bit of time to switch.