Author Topic: Is Rosie a high frequency or low frequency inverter  (Read 236 times)

qrper

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Is Rosie a high frequency or low frequency inverter
« on: September 08, 2021, 11:35:45 AM »
Well guys, the subject line says it all

Does Rosie use  low frequency switching (and has a nice big transformer inside) or high frequency switching sans transformer?

mike
System one: 7kWp w/ Trina 250 W panels @90 Vdc. Classic 150 to 16-6 V U.S batteries. Trace 5548 sine wave inverter.
System two: 6kWp grid tie with solaredge inverter.
System three: Midnite Brat, two 120 W Astropower modules, 100 Ah battery. Runs the LED streetlight in the back yard.

boB

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Re: Is Rosie a high frequency or low frequency inverter
« Reply #1 on: September 08, 2021, 10:17:30 PM »

The Rosie and B17 are high frequency (~ 30 kHz)  BUT they are not transformerless.

Most all battery based inverters have a transformer for isolation.  Sometimes  company's will say their inverter is transformerless but in reality, most of them are.  All of them that I know of are but they don't have to be of course.

Even the heavy ones these days with a 60 Hz transformer are actually high frequency as well.   They are just single conversion too, in that the low voltage primary battery side is where the switching is done and not really much is done on the secondary side.  This also puts all of the battery ripple current (120 Hz) on the battery since there is no energy storage  on the high-voltage side of the transformer like a true high-frequency inverter/charger.

Rosie and the B17 are much harder to do than the low frequency transformer ones  Until recently, say, last 10 years, it wasn't as easy to do what we are doing.  Most of those low frequency transformer inverter/chargers are old designs.

Now days you also have the hybrid inverter/chargers like our Chinese DIY inverters and the Sol-Ark inverters (also Chinese) that have isolated high-frequency transformers BUT also a NON-isolated (no transformer) from the PV input to AC output (or grid).

So yes, they are high frequency products.  What I like about them is that they are lighter weight than the big transformer ones.

I think the B17 is really cool because the inverter/charger modules are like, 12 pounds or so and you can make up a 15 kW inverter system without having to lift hundreds of pounds of stuff !   I think the mainframe might be 40 pounds ?  I weighed a Rosie a year and 1/2 or so ago and it was around 35 pounds.   That is going to me more now though because of the big heat-sink.  It really doesn't need such a big heat-sink in my opinion though.




K7IQ  He/She/It

qrper

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Re: Is Rosie a high frequency or low frequency inverter
« Reply #2 on: September 09, 2021, 02:52:54 PM »
Thanks, boB

I was wondering. I've seen the videos of Rosie starting the air compressors, and remember thinking that the high frequency inverters generally have a harder time meeting surge current requirements than the heavy iron low frequency inverters do.

I have this grandiose idea of moving my old Trace SW5548 from the basement to the garage this winter. I haven't quite talked myself into carrying that beast up the steps at 100 pounds. I was in younger man's clothing when I installed it. (and it down the steps and not up!) Might need some help.

mike
System one: 7kWp w/ Trina 250 W panels @90 Vdc. Classic 150 to 16-6 V U.S batteries. Trace 5548 sine wave inverter.
System two: 6kWp grid tie with solaredge inverter.
System three: Midnite Brat, two 120 W Astropower modules, 100 Ah battery. Runs the LED streetlight in the back yard.

Vic

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Re: Is Rosie a high frequency or low frequency inverter
« Reply #3 on: September 09, 2021, 05:41:44 PM »
Hi Mike,

Do yourself a favor,  and get some help to move the SW.  IIRC,  the SW 5548 Plus weighs about 135 pounds,  and it might be a bit lighter than your SW 5548.

These are very capable inverters,  as you know.  73,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

boB

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Re: Is Rosie a high frequency or low frequency inverter
« Reply #4 on: September 09, 2021, 11:04:29 PM »
Yes !   That SW5548 is a very heavy inverter !   People still swear by them though.  In a good way   :)

I am really happy with the surge capability and continuous power of these HF inverters.   

Better low voltage and high voltage MOSFETs are probably why they work so well.  Parts have gotten way better since the  SW series and similar inverters.   I remember we were working on a HF inverter back at Trace Engineering in the late 1990s.  The guys working on that, which were top notch engineers, gave up.

Here is a pic of the SW waveforms many years ago I made of the 3 transformer outputs placed in series to make the SW series output...

The higher frequency waves would change with battery voltage to keep the output regulated to 120 VAC...
K7IQ  He/She/It