Has anybody used the Rosie inverter yet for prime time?

[Hedges]

I don't think the transformer after the inverter helps with split-phase motors.

I do see "motor starting transformers" which seem to be auto-transformers, reducing voltage and increasing current, for 3-phase motors. But 3-phase motors have good starting torque. Split phase motors have poor torque.

Modern LF sine wave inverters use HF switching. But they use LF transformer to step up from something like 40V peak to 170V peak. There is heating of the transistors during switching transitions, so both could be subject to the same aging. Better power transistors today, so maybe can be as reliable as the old LF inverters.

I've had SMPS die just being used. Transformer type power supplies only due to overload - some are "impedance protected", supposed to be able to handle shorted output.

The difference is probably quality, of parts and design. My 24 year old Honda still runs fine, with ECU driving ignition coil and injectors. A large inverter of course is carrying much more current; maybe if designed with transistors sufficiently oversize they are reliable. Then there is the effect of various loads which present short circuit (motor starting) and voltage spikes from inductive kick.

We don't know how reliable Rosie will be, but Midnight should have a fair idea. Right now we're hearing about test of heavy loads that might be within its specs, but without measurement can't know for sure. This was a 5 HP induction motor. Midnight had demoed starting 4x 1.5 HP air compressors, but those were brush-type motors so easier.

An induction motor with full-load current near inverter spec'd output is something we wouldn't have expected an inverter to start at all.
The 5 HP motor is likely 6.4kVA under load, and I expect starting current 5x as great or 30 kVA. That is twice Rosie's specs.

 

[realpinochet]

Thx. I'm seeing it now. A little.

I guess what I'd want to know (and I guess more or less why you started this thread), does anyone believe a Rosie will do what an XW will do, time and time again, for 10 or 15 years trouble free? I guess some people believe these newer Sol-Arks will and if you open up that can of worms with doubt, 'them's fightin' words'. ( "how dare you compare my 'golden calf' Sol-Ark with your pagan XW!" )

But seriously, can a HF really be as Reliable as a LF long term for grid replacement whole house loads ?

I doubt it! I'd like to be proven wrong. The massive torodial transformer in the xwpro is the secret sauce and it can take the brunt and beating of heavy long surges year after year. It's just a huge hunk of metal. I'm assuming,Rosie and the like, uses large caps to achieve similar results. Just my opinion but I'd think caps would wear out and bulge / leak over time.

 

[Hedges]

I think caps can carry a few cycles of AC. I measured 120 Hz ripple of around 3V or 1% out of 300V for PV input of GT PV inverter. Larger caps and elevated voltage, 50% dip could carry a few seconds. Comes at a cost of efficiency; inverters are most efficient when DC power rail is close to Vpeak, lowest voltage conversion in inductor circuit. So holding energy stored in higher voltage caps is either a separate circuit just for surge, or reduced efficiency all the time.

Ripple current is what heats capacitors and can wear them out. They might be thought to have a 7 year life, but I've seen about 20 years without failure for GT PV inverters (operating maybe 12 hours per day.) SMA warrants GT PV inverters for 20 years, battery inverters for 10 years.

If Rosie has many minutes at modest overload, that is a thermal limit. If several seconds surge, 15kVA long enough to start a motor, I think that is a boost converter from 48V to 170V (or 340V) able to deliver the current for a limited time. 2x the continuous full-load current, so 4x the heating of transistors and inductors. Similar specs for Sunny Island, except longer surge current: 60 seconds, 60A @ 240V = 14,400 VA (SI only claims 3 seconds at 2x rating.) Likely the time to heat up thermal mass of heat sink. 60A x 240V / 48V = 300Arms in transistors for battery side. I^2R heating of 90W per milliohm, however many milliohms of FET and inductor winding.

I think cheap inverters have barely enough current handling in boost circuit for 1x rating. The buck circuit from HV rail to AC output only carries a fraction the current. Cheaper to get higher voltage transistors than higher current.

 

[rhino]

Still nobody here has gotten one??

 

[rhino]

I did notice they updated their website featuring the Rosie, Barcelona, and Hawke's Bay. https://www.midnitesolar.com/

 

[SpongeboB Sinewave]

"SpongeboB Sinewave" if you want to summon the Lord king of Midnite.

Just found this thread today ! Still reading. From what I've read so far:

Rosie does surge very well.

Stacking is now working but I don't know if we have actually released that firmware update yet. We are testing thoroughly before we release.

AC coupling (as in with GT inverters) will work but we are still adding frequency shifting which would also be a firmware update when ready.

boB

 

[SpongeboB Sinewave]

Good question....another decade maybe. lol

B17 is still coming. Time and resources have been moved around temporarily to improve production and testing of Rosie inverters and the two 600V MPPT charge controllers. If these were being manufactured in China, we would have more time for engineering itself.

Having said all that, the B17 internals are very similar to the Rosie so work on Rosie production and testing has a direct impact on ongoing B17 engineering.

boB

 

[realpinochet]

B17 is still coming. Time and resources have been moved around temporarily to improve production and testing of Rosie inverters and the two 600V MPPT charge controllers. If these were being manufactured in China, we would have more time for engineering itself.

Having said all that, the B17 internals are very similar to the Rosie so work on Rosie production and testing has a direct impact on ongoing B17 engineering.

boB

So that means Rosie has a bigger heavy duty sister...are we going to see a 15Kw inverter soon? Perhaps her name could be Bertha. Curious do you guys have plans for larger inverters and do you guys plan on every getting into the high voltage DC side that the industry seems to be interested in? I'm still interested to see the current Rosie abused next to a xwpro and outback. Thanks Sir for chiming in.

Edit: And for the love of God some 200A relays for pass through..makes it so much easier.

 

[SpongeboB Sinewave]

I my opinion ...America First all the way. I believe Schneider said it was made in either india or mexico.

Schneider and Victron are made in India. I'm sure parts are from worldwide sources including China.

MidNite uses some parts from China too but we definitely try and do use parts locally such as sheet metal and bus bars, connectors, etc.

We also build a lot of parts in house. Most inductors and some transformers for instance have been made in house for many years.

Who knows where a lot of the semiconductors and passive components come from ? All over the world I seem to find.

Wire... Copper for wire and bus bars. Ferrite and powdered iron cores and toroids. Filter capacitors.

SMT components like resistors and capacitors. Aluminum and castings. Solder. LCDs. Rubbery buttons.

Screws, nuts and bolts are purchased locally but where are they actually made ?

Relays. GOOD relays. GOOD electrolytic capacitors ? Not from the US unfortunately.

Plastics. Lots of custom plastic parts. I could go on and on.

boB

 

[Hedges]

Any info on how well Rosie handles AC coupling in case of load-dump, where it suddenly has to charge battery from AC? People have said HF AC coupled can't reverse direction of power flow the way LF can, but I don't understand the details.

So that means Rosie has a bigger heavy duty sister...are we going to see a 15Kw inverter soon? Perhaps her name could be Bertha.

Paralleled and hot swappable. (alternative would be one box with more transistors in parallel)
This gives redundancy, like power supplies for a server.

 

[SpongeboB Sinewave]

Found these threads over at MN... for rosie. One guy in Texas say his 5hp air compressor tripped it but not enough info on the compressor.

The Rosie

The Rosie

midniteftp.com

I know that sometimes a 5 HP, full of air, compressor will trip the Rosie. But sometimes it doesn't. Depends on the compressor and if it is full or not I guess.

boB

 

[Hedges]

LRA probably exceeds Rosie's surge rating, but it still gave a good try.

FLA of 5 HP x 5x multiple for starting surge was well over Rosie's surge rating.
Longer surge rating than most inverters, so anything that reduced the peak in exchange for longer start-up might be OK.
Compressors of course build backpressure as they start.

I know that sometimes a 5 HP, full of air, compressor will trip the Rosie. But sometimes it doesn't. Depends on the compressor and if it is full or not I guess.

boB

Unloader is supposed to enable starting regardless of pressure in tank.
I think operating current of 5HP is well within Rosie's specs. Is it happy with the phase shift and PF of an induction motor?

 

[SpongeboB Sinewave]

Any info on how well Rosie handles AC coupling in case of load-dump, where it suddenly has to charge battery from AC? People have said HF AC coupled can't reverse direction of power flow the way LF can, but I don't understand the details.



Paralleled and hot swappable. (alternative would be one box with more transistors in parallel)
This gives redundancy, like power supplies for a server.

Always trying to improve regulation speed. That is what you are talking about here I'm pretty sure.

Rosie and B17 are completely bi-directional so no waiting.

boB

 

[realpinochet]

LRA probably exceeds Rosie's surge rating, but it still gave a good try.

FLA of 5 HP x 5x multiple for starting surge was well over Rosie's surge rating.
Longer surge rating than most inverters, so anything that reduced the peak in exchange for longer start-up might be OK.
Compressors of course build backpressure as they start.



Unloader is supposed to enable starting regardless of pressure in tank.
I think operating current of 5HP is well within Rosie's specs. Is it happy with the phase shift and PF of an induction motor?

You probably know this answer Hedges...in your opinion would inverters be able to surge higher and longer if the DC input was a higher voltage to begin with? Seems like a 300-400 VDC would be more efficient because it doesn't have to work as hard. It would run a lot cooler to and less / smaller wiring.

 

[Hedges]

Frequency shift to regulate can't be too fast without upsetting AC loads. Also affects current draw of motors.
Typically we see a few seconds to shift frequency and regulate power, so that has to get stuffed down into batteries (I don't understand why voltage-watts wouldn't immediately curtail output if battery inverter can't absorb the power.

"Completely bidirectional" - is that different from other HF inverters that do AC coupling? (SolArk, Skybox)

 

[Hedges]

You probably know this answer Hedges...in your opinion would inverters be able to surge higher and longer if the DC input was a higher voltage to begin with? Seems like a 300-400 VDC would be more efficient because it doesn't have to work as hard. It would run a lot cooler to and less / smaller wiring.

Easier to do I think. Smaller inductors, and easier to get higher voltage/lower current transistors.
I think it is just V x I = W, can be done with any voltage.
As Rosie and some others have shown, surge can be high with HF, but the parts have to be sized to deliver the current, and heatsinked sufficiently.

I think a key issue is that boost converters have to pump up the current over multiple HF switching cycles, and power delivery is limited to energy stored in the inductor.

A pure LF inverter (not using HF buck to drive the transformer) can drive MSW and surge current is massive, large multiple of whatever it was rated for. So long as transistors can deliver the current. I understand transformer core saturation, but I don't have a good handle on what limits the current which can be transferred. I do understand that power transformers with "3% regulation" have IR drop from +3% to -3%, leaving another 97% for voltage to reach zero. That lets short-circuit current be 15x rated current. A transformer that can deliver 200A to your house can deliver 3000A into a short. Same concept should help surge current of an inverter.

Trace reportedly did MSW with multiple transformer taps, so the modified square wave became multiple steps, and cleverly engineered transformer non-ideality filtered it.

I have a couple ideas of how buck converter could support greater surge from modern LF (with HF buck) inverters.

 

[realpinochet]

Easier to do I think. Smaller inductors, and easier to get higher voltage/lower current transistors.
I think it is just V x I = W, can be done with any voltage.
As Rosie and some others have shown, surge can be high with HF, but the parts have to be sized to deliver the current, and heatsinked sufficiently.

I think a key issue is that boost converters have to pump up the current over multiple HF switching cycles, and power delivery is limited to energy stored in the inductor.

A pure LF inverter (not using HF buck to drive the transformer) can drive MSW and surge current is massive, large multiple of whatever it was rated for. So long as transistors can deliver the current. I understand transformer core saturation, but I don't have a good handle on what limits the current which can be transferred. I do understand that power transformers with "3% regulation" have IR drop from +3% to -3%, leaving another 97% for voltage to reach zero. That lets short-circuit current be 15x rated current. A transformer that can deliver 200A to your house can deliver 3000A into a short. Same concept should help surge current of an inverter.

Trace reportedly did MSW with multiple transformer taps, so the modified square wave became multiple steps, and cleverly engineered transformer non-ideality filtered it.

I have a couple ideas of how buck converter could support greater surge from modern LF (with HF buck) inverters.

Almost sounds like you're saying a Hybrid of a LF/HF where the inverter can have a small toroidal transformer to assist the initial surge?

 

[Hedges]

Simply putting a transformer after inverter doesn't help surge.

In some cases, step-down transformer helps. I've seen transformers for starting 3-phase motors. Obviously reduces surge current at reduced voltage. Motor has to be able to produce the torque to start. 3-phase has better low speed torque.

Trace approach of switching a transistor on hard, connecting transformer primary to battery, delivered high current into low impedance. Any LF MSW with transformer would do that. (Or, I guess, HV battery with H-bridge and nothing else?) An HF inverter is limited by power it can boost from LV battery to HV rail.

I think modern LF inverters have battery, buck converter, H-bridge, transformer. It appears Sunny Island uses 42Vpeak primary, 170Vpeak secondary, based on efficiency vs. voltage curves. The buck converter has to be able to deliver the surge. Self-heating would be what limits its 3 second surge, and current capability gives it 11kW (92A) 3 second surge and 180A 30 ms surge (good for tripping breakers, nothing else.)

Rosie probably sized components and designed cooling so surge could last 60 seconds. Putting the heat into heatsink mass but not transferred to air.

 

[realpinochet]

Simply putting a transformer after inverter doesn't help surge.

In some cases, step-down transformer helps. I've seen transformers for starting 3-phase motors. Obviously reduces surge current at reduced voltage. Motor has to be able to produce the torque to start. 3-phase has better low speed torque.

Trace approach of switching a transistor on hard, connecting transformer primary to battery, delivered high current into low impedance. Any LF MSW with transformer would do that. (Or, I guess, HV battery with H-bridge and nothing else?) An HF inverter is limited by power it can boost from LV battery to HV rail.

I think modern LF inverters have battery, buck converter, H-bridge, transformer. It appears Sunny Island uses 42Vpeak primary, 170Vpeak secondary, based on efficiency vs. voltage curves. The buck converter has to be able to deliver the surge. Self-heating would be what limits its 3 second surge, and current capability gives it 11kW (92A) 3 second surge and 180A 30 ms surge (good for tripping breakers, nothing else.)

Rosie probably sized components and designed cooling so surge could last 60 seconds. Putting the heat into heatsink mass but not transferred to air.

I mean insider the inverter as a stage one...which is why I was saying a hybrid inverter. Another words take a HF inverter today and put in a small transformer to handle the initial hit. That should reduce heat and stress on the Caps and other transistors.

 

[MrM1]

Noob Question, but do these modern HF inverters spell the "end" of LF inverters in most residential cases? Would something like the Rosie fare well against say an XW?