Midnite Solar Announced their new 10kw AIO at Intersolar Today

[timselectric]

I never really understood where the "low frequency" naming came from. The transformer changes the voltage, not the frequency.

 

[andrew-d]

Here is the spec sheet for the new AIO

Small typo: under "Operating Temperature Range", you have "(>450 derating)", which I assume is supposed to be "(>45C derating)", or "(>45º derating)".

Thanks for sharing!

 

[Quattrohead]

Well then, everyone else has had it wrong in this forum. Because every unit with a transformer is referred to as low frequency.
And 90% of them have autotransformers.

Two different things being confused here yet again thanks to the wonky American split phase system.

 

[Hedges]

What we now call LF has an isolation transformer with battery voltage applied to primary, AC voltage on secondary.
I think my Sunny Island is 42V in, 170Vpeak out.

But these actually have HF PWM to synthesize sine wave.

What we call HF inverters just use inductor or HF transformer to create boosted AC voltage. Or, HV battery, just buck or buck-boost to AC voltage with HF inductor or transformer.

A true LF inverter would be MSW, like 12V applied to primary, 170V from secondary. Or multiple transformer taps to make staircase. Like early Trace and Warpverter.

Putting an auto-transformer or an isolation transformer after an HF inverter, inside or out, does not make it LF.
But when the transformer is step-up from 48V battery to 120 or 120/240Vrms, we call it LF. Not sure that is accurate.

Transformer does not do anything to provide high surge. MSW architecture does, limited I think to fault current capability of transformer (many times nominal.)

HF can have surge if transistors and boost inductor can deliver it. Usually limited in time due to heating.

 

[timselectric]

Two different things being confused here yet again thanks to the wonky American split phase system.

What does split-phase have to do with it?
Transformers are used all over the world.

 

[Hedges]

No Hyper VOC so don't go over 600V

Can you roll out Hyper VOC with a firmware update?

Or is the MPPT not sufficiently configurable, or something like capacitors not rated for higher voltage?

 

[timselectric]

Transformer does not do anything to provide high surge.

It does, when referring to a single leg surge.

 

[SpongeboB Sinewave]

Bob was posting about this the other day:

Midnite Solar Rosie on sale

Sounds like a lose-lose. If you give your blueprints and essentially your IP to a Chinese firm, what is to prevent them from delivering an inferior product and materials under your contract, opening up another company manufacturing an AIO with relatively superior materials selling them under a...

diysolarforum.com

That would have been Robin. I am in AZ right now recuperating from some health issues. Working while recuperating of course !
I love my little lab here !

boB

 

[Hedges]

It does, when referring to a single leg surge.

Yes, a transformer can transfer power from 240V to 120V or vice versa. So could give 2x if big enough.
But it doesn't store energy to any appreciable degree or otherwise help with surge.

I think the most dramatic effect is in a true low-frequency configuration like MSW.
A utility transformer spec'd 3% regulation might deliver 0A at 123.6V, 100A at 116.4V. If you short-circuit the output, it could deliver 3000A or more.
Similar the surge capability of MSW, if the transistors could carry the current.

Anything HF uses SMPS to store energy in an inductor. What it can do is limited by stored energy and switching frequency.

 

[timselectric]

Yes, a transformer can transfer power from 240V to 120V or vice versa. So could give 2x if big enough.
But it doesn't store energy to any appreciable degree or otherwise help with surge.

Correct

I think the most dramatic effect is in a true low-frequency configuration like MSW.
A utility transformer spec'd 3% regulation might deliver 0A at 123.6V, 100A at 116.4V. If you short-circuit the output, it could deliver 3000A or more.
Similar the surge capability of MSW, if the transistors could carry the current.

Anything HF uses SMPS to store energy in an inductor. What it can do is limited by stored energy and switching frequency.

I'll just take your word on most of this. It's over my pay grade. lol

 

[Cheap 4-life]

Excellent news Robin & Halfcrazy.
I don't care where it's made, as long as it is made well & to robust specs.
I found the "Art-Deco" comment funny... I like Art-Deco myself, it's COOL ! Architects should bring it back with a modern twist IMO.

Dang thing about it.... Those of us who have Classics & are all setup would have to swallow a Big Chunk to convert over... I dunno many who'd want to sacrifice a few grand worth of SCC's that work amazingly well.

There needs to be an option from them with ALL the capability of this inverter without the built in chargecontroller..

 

[SpongeboB Sinewave]

As far as I know, every battery based inverter out there have a transformer at least between battery side and HV inverter grid side.
The PWM that makes the sine wave is always high-ish frequency. Usually greater than 20 kHz so it falls outside of the human hearing range.

"Low Frequency" just refers to the transformer being a heavy 50Hz or 60Hz type which is BIG compared to a "High Frequency" inverter which uses a smaller transformer. Low Frequency transformer inverters have typically been said to have a higher surge than HF inverter types but there is no technical reason for this to be the case.

boB

 

[DIYrich]

We will be looking for the best places to give away the first 20 units. We need to get the most out of these marketing units as there is a ton of competition. Some of it is pretty good, but a lot of it misses the mark.

Feel welcome to send one my way. I will be adding solar to a Sol-Ark 15k with a battery. It is a unique use case for the MS Inverter, but would serve as a demonstration for the general concept:

The MS inveter would attach as AC Solar Input to the Sol-Ark. The 10kW rating of the MS inverter is perfect for my situation.

The Energy Storage Solutions (ESS) program in CT pays a fee (incentive payment) based upon how much your battery supports the grid during "Events" set by the Utility (3 hour window on a specific day when they expect peak demand). Battery ability is after PV production.

My batteries can max out the sol-ark 15k inverter output for that 3 hour window. If I add DC PV, then that cuts into inverter capacity available for the incentive payment.

Why not add a 2nd 15k? Because the utility (Eversource, or ES) limits export to 25kW. Two 15k's can exceed the limit. ES doesn't care about software limits (grid export limit), ES is concerned with hard limits.

Adding 10kW of AC PV would be allowed - the rated AC output of the MN15 (I think I can ignore the peak output of 11kw).

Any excess PV (over 10kW) could be used to charge the batteries (offset power being drawn by Sol-Ark to export power). ESS program only sees what the Sol-Ark inverter is doing, not where the battery power comes from.

Why would MS care about this special case? It could demonstrate that the MN15 could serve as UL1741SB compliant AC PV input to another inverter that can modulate AC PV input.

Bonus if MN15 priority of Solar PV can be: Load, Export, Recharge Battery. And, if Export is Frequency Limited, then excess PV is sent to Batteries. Only when batteries are fully charged would PV production be throttled back.

 

[Hedges]

I'll just take your word on most of this. It's over my pay grade. lol

Simple calculation is just ohms law, current limited by winding resistance.
Beyond that is what the core can transfer, I'm not real clear on it.

Transformer Fault Current Calculator With Calculation Formula | Electrical4u

Enter the transformer rating in kVA (kilo Volt-Amp), Enter the secondary terminal voltage in volts and the percentage impedance in %. Then press the calculate

www.electrical4u.net

 

[G00SE]

Here is the spec sheet for the new AIO

Where do I send my money, I’ll buy one right now ?

 

[timselectric]

Simple calculation is just ohms law, current limited by winding resistance.
Beyond that is what the core can transfer, I'm not real clear on it.

Transformer Fault Current Calculator With Calculation Formula | Electrical4u

Enter the transformer rating in kVA (kilo Volt-Amp), Enter the secondary terminal voltage in volts and the percentage impedance in %. Then press the calculate

www.electrical4u.net

I wasn't referring to the transformer stuff.
The electronic stuff is beyond my expertise.

 

[Halfcrazy]

Unless I am missing seeing it there does not seem to be a rating for idle current.

Right at 60 watts running with no loads and no power save modes on

 

[Checkthisout]

Do these AIO's allow battery charging with the inverter portion off, both from an a/c source and of course the MPPT?

 

[Zwy]

I don't have the full spec sheet, but Midnite has a very impressive unit on the way. I spent about an hour at Intersolar talking to the brains behind the operation and was very impressed. Unlike some competitors, the Midnite team was very humble and pleasant to talk to and they didn't belittle the small businesses they work with. We agreed to get one of these AIO units at the end of February when inventory arrives and will use this thread to share everything we can learn about this machine.

Some specs:
PV Input voltage up to 600VOC, MPPT operating range of 70V to 550v (this is a higher top and lower bottom than SA and EG4)
3 MPPT inputs
48v battery input
100A passthrough/transfer switch
15kW solar input
10kW continuous inverter
Surge: 13kW on a single leg (WOW!)
Field serviceable! First AIO to have this ability.

To get things started, a picture!

View attachment 189615

Good news, I've been researching inverters for my shop solar system. This is a serious contender.

 

[AntronX]

So I am very interested to learn what is limiting the continuous output. (Heat dissipation?)

Yes. At surge power levels HF transformer efficiency gets worse and heat becomes exponential. Same happens to LF transformers.

 

[timselectric]

Yes. At surge power levels HF transformer efficiency gets worse and heat becomes exponential. Same happens to LF transformers.

Absolutely.
If it is a transformer that is providing surge capacity.
I don't think that it's been confirmed either way, yet.
But I would expect it to be the case.

 

[AntronX]

If it is a transformer that is providing surge capacity.

It has to. There is no other long term energy storage on HVDC bus. HV Capacitors are only good for milliseconds.

 

[Danke]

Where do I send my money, I’ll buy one right now ?

 

[timselectric]

It has to. There is no other long term energy storage on HVDC bus. HV Capacitors are only good for milliseconds.

I agree completely.

 

[42OhmsPA]

You could comfortably run 18s packs...
~2KWh additional capacity per 305ah pack.

Will there be a pre-order available?
I'm perfectly happy with what I have but this is a solid unit with excellent specs.

I bet one could make a very popular youtube video putting this head to head with some other popular AIOs...