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Posted By Topic: Interactive inverter

Rhino
Feb 04 2019 10:23

4509.1
9.4.2. Output of genset can only be connected via Fixed wiring, use of plug is not permitted for interactive inverters.

Sounds like this prohibits the use of appliance inlets for inverter/chargers that synchronise with AC sources?

Prohibits the use of these inverter/chargers in connectable installations as well which can plug into mains or a genset?

   

pluto
Feb 04 2019 12:10

RhinoFeb 04 2019 10:23
Your comment 1
4509.1
9.4.2. Output of genset can only be connected via Fixed wiring, use of plug is not permitted for interactive inverters.

Sounds like this prohibits the use of appliance inlets for inverter/chargers that synchronise with AC sources?

My comment 1
The key word is "interactive inverters" these are inverters that have the ability to "import" and "export" power from the inverter assembly.

A "grid-connect" inverter is an example of an "interactive inverter".

Because of the ability öf interactive inverter to "export", the use by a plug is prohibited as the pins of the bare pins of the plug would or could become alive when export occurs from the interactive inverter.


   

Rhino
Feb 04 2019 12:50

Yes i suppose it is a possibility,

The inverter/chargers that do have the ability to export by default dont export, they normally require technical programming and set up to allow this to happen.

But yes small possibility customer could change settings
   

AlecK
Feb 04 2019 16:09

when an inverter / charger is put into a connectable installation, the purpose is generally to use the battery to provide an LV a.c. supply to the SAME sockets etc that are normally supplied from external (grid / genset) supply via the supply lead.
Unless there is a proper change-over switch, that automatically livens the plug pins of the supply lead / appliance inlet.
and that's dangerous.

Not a small possibility of a hazard but a guaranteed hazard.

Currently "3001" does NOT permit that set-up - yet people keep trying to build it.

And of course if there is only a simple change-over switch, the charger side of the thing can't work because the inverter unit will be - MUST be - isolated from both the external supply and the load(s).

Different for a UPS type set-up; where the unit supplies output via a different set of connections, and thoise loads are only ever supplied via the UPS (or a UPS by-pass switch.; and there's no back-feed risk.
   

Rhino
Feb 05 2019 11:02

There are inverter chargers that synchronise and there are also inverter chargers that don’t synchronise with the incoming AC Source (grid or genset).

The ones that do synchronise normally have the ability if programmed to back-feed to the grid and they can also can provide power assistance eg 3000W inverter charger plus 3000W available from grid means Output = 6000W.

The ones that don’t synchronise simply have an internal transfer relay and when an AC source is detected within its parameters it closes the transfer relay, now the output is equal to the input ( grid or gen).

Your comment;
when an inverter / charger is put into a connectable installation, the purpose is generally to use the battery to provide an LV a.c. supply to the SAME sockets etc that are normally supplied from external (grid / genset) supply via the supply lead.
Unless there is a proper change-over switch, that automatically livens the plug pins of the supply lead / appliance inlet.
and that's dangerous.

Not a small possibility of a hazard but a guaranteed hazard.

My Comment;

Yes the above set up just won’t work it is a guaranteed hazard.

However I think what people are trying to do is connect the supply of the connectable installation DIRECTLY to the AC input of the inverter charger, therefore when grid/gen is connected, the inverter charger provides grid / gen power directly at its AC output and also charges the batteries at the same time.

If it is a synchronising inverter charger then there is a small possibility of the appliance inlet becoming live if programmed to “grid Feed” .
Normally the grid feeding function is set to no by default. When kept like that, it should never back feed because there is always small part of the load taken from the AC source(grid or gen).

This set up I assume you are referring to as a UPS set up? however in a connectable installation its normally in back up mode as opposed to standby mode waiting for a ‘grid outage’. This is maintained as solar normally keeps the batteries charged.

   

pluto
Feb 05 2019 16:10

AS/NZS 3001 is currently being revised and there are some changes in the area in the use of inverters as an energy source in connectable installations.

But you will have to wait and see what get changed as all the changes have not been worked through yet.

Remember AS/NZS 3001 has to cover domestic, mobile medical facilties and some other specialised connectable installations and it is too early to say what the full extent of the changes will be.

There are a number of smart inverters available and which ones will be used will be depend on cost, weight and abilty for them to be electrically safe at all times.
   

dbuckley
Feb 06 2019 11:49


Pluto notes:

> AS/NZS 3001 is currently being revised and there are some changes in the area in the use of inverters
> as an energy source in connectable installations ... which ones will be used will be depend on cost, weight and
> abilty for them to be electrically safe at all times.

I take it the cost and weight is just commentary and won't be a feature of the standard :)

The other thing that actualy did bug me was from an earlier comment in the thread:

> A "grid-connect" inverter is an example of an "interactive inverter".

> Because of the ability öf interactive inverter to "export", the use by a
> plug is prohibited as the pins of the bare pins of the plug would or could
> become alive when export occurs from the interactive inverter.

Whereas this is true, connectors exist that are touch-safe at all times, and thus a blanket prohibition against connectors isn't necessary, it's just clumsy. The prohibition could be worded better to ensure safety whilst not prohibiting what would be a functionally useful thing.

   

AlecK
Feb 06 2019 13:14

In the context of what ESRs call "connectable installations" and the relevant standard calls "transportable structures"; the types of plug, cord connector, and appliance inlet that may be used are limited.
That's called "standardisation" and is done to ensure - so far as practicable - that a CI (eg a caravan) can plug in wherever they go, without need for adaptors.

None of the permitted types has shrouded pins. However there is a "loophole" that allows other types for special applications.

Allowing other types for caravans with inverter/chargers would be silly; because the caravan parks they plug into won't have suitable sockets - and using an adaptor would defeat the purpose of using a shrouded-pin plug.
We're NOT about to require every caravan site in the country to provide a different socket just in case someone comes along with an inverter/charger unit. Instead the connector types will continue to be restricted, both for initial construction and for issue of WoEF.

And the rules requiring avoidance of back-feed will remain in place - they are there for very good reason.

Those who want to incorporate such equipment into their motorhome (or boat) must do so in a way that complies with the Standard. That won't change.

What may change is that some guidance may be offered WRT using UPSs, and the very limited guidance there now for using inverters may be expanded.


   

Rhino
Feb 07 2019 09:38

Your comment

Different for a UPS type set-up; where the unit supplies output via a different set of connections, and those loads are only ever supplied via the UPS (or a UPS by-pass switch.; and there's no back-feed risk

My comment

Does this not create a loop-hole where it can be set up as a UPS instead of a SAPS therefore avoiding the restrictions of SAPS?
   

AlecK
Feb 07 2019 09:47

That's the sort of thing the committee will have to think about when seting revised requirements
   

pluto
Feb 07 2019 12:23

I make comments on behalf of NZ on the IEC papers, draft standards which arrive in NZ on a weekly basis.

And I give some background on the current world position on the use of the term grid-connect inverters.

I have recently seen the IEC documents on the proposals being firmed up to provide both way power transfer from Electric Vehicle batteries in the car; or, fixed battery banks able to be charged by PV arrays'; or wind turbines; or, mini-hydro turbines and this electronic device as able to do power conversions both ways and able to operate in standalone mode and also supply an electrical installation without the mains supply being available.

All this group of devices is known by the IEC as a GRID-CONNECT inverter.

Some types of the above Grid-Connect inverters are required to have earth leakage protection on the DC inputs and an Isolated Input to output inverter on each DC input.

These standards are published except for the electric vehicle version and publication of that standard is expected to be mid 2019.

I would expect that both AU and NZ will use direct text adoption of these IEC standards so that the long development time of locally produced AS/NZS standards can be eliminated.

These devices will be software controlled type devices, made overseas (unlikely to be AU) and I would expect that the use of the term of UPS may disappear too in the near future, due to the universal nature of this new generation of Grid-connect inverters.