What voltage is required to make SUNNY TRIPOWER CORE1 33kW work?

dks1

My local utility on my building is 220V-240V 3Ø Delta. Is the output voltage of Core1 480V aswell? Should i use a step-down transformer or a step-up transformer? In the manual the installation videos it shows that INPUT is from PV voltages. Then the OUTPUT is already 480V neutral. Meaning i need to stepdown this output to connect to the local Grid? Any help highly appreciated.

Dks1

BB.

I am way out of my league here... But you need (I think) a reverse feed 240 VAC Delta to 480 VAC Wye type transformer... Something like this:?

https://store.maddoxtransformer.com/collections/general-purpose-600v-class-dry-type-transformers/products/copy-of-3-phase-240v-delta-480-y-277-step-up-transformer?variant=2194321342473

A 45 kWatt is just over $2,000 list price--At least it gives you a starting point for planning.

They do have this information about reverse feeding a standard step down transformer vs an engineered step up transformer:

https://store.maddoxtransformer.com/products/480-delta-240-delta-120?variant=45588248521

This transformer can be reverse fed to achieve a step up from 240V to 480V, but the adjustment taps do not work if you do this, and the inrush is greater than using a specially designed step-up transformer.  You can buy a true step-up transformer here.

Read more about reverse feeding.

You may also have to research the grounding of the Delta from the utility vs the grounding of the neutral Wye on your 480 output of the transformer (isolated or not)...

I know nothing about the company, website, or their products... But I would certainly make a phone call/email/contact their engineering department. They can probably give you much better information than I....

-Bill

dks1

BB. said:

I am way out of my league here... But you need (I think) a reverse feed 240 VAC Delta to 480 VAC Wye type transformer... Something like this:?

https://store.maddoxtransformer.com/collections/general-purpose-600v-class-dry-type-transformers/products/copy-of-3-phase-240v-delta-480-y-277-step-up-transformer?variant=2194321342473

A 45 kWatt is just over $2,000 list price--At least it gives you a starting point for planning.

They do have this information about reverse feeding a standard step down transformer vs an engineered step up transformer:

https://store.maddoxtransformer.com/products/480-delta-240-delta-120?variant=45588248521

This transformer can be reverse fed to achieve a step up from 240V to 480V, but the adjustment taps do not work if you do this, and the inrush is greater than using a specially designed step-up transformer.  You can buy a true step-up transformer here.

Read more about reverse feeding.

You may also have to research the grounding of the Delta from the utility vs the grounding of the neutral Wye on your 480 output of the transformer (isolated or not)...

I know nothing about the company, website, or their products... But I would certainly make a phone call/email/contact their engineering department. They can probably give you much better information than I....

-Bill

Bill,

What do you mean by a reverse feed 240VAC DELTA to 480VAC WYE? I consulted with my REE and he said since the Core1 SMA inverter has an output of 480V i should need a step down transformer with an input of 480V and and output  of 240V.. Any thought before i male a $2,000 mistake.. thanks! Yoir reply would be highly appreciated..

dks

BB.

For normal homes and businesses, step down (buck transformers) are used. Higher voltage input/lower voltage output.

As I reread your first post, I see that I miss understood your application and you need a step down transformer... The link about "reverse" feed, buck transformer will work as a boost transformer but it takes more current to start (inrush current). And the minor voltage adjustment (taps) do not work the same as in buck mode.

Anyway... Since you are looking for a step down transformer (buck) to drop from 480 to 240 VAC--Then you do not have to worry about the using a standard buck transformer in "reverse" (boost) operation (or purchasing a boost/step up "designed/wound" transformer).

Again, I am no expert here... Work with your supplier's engineer(s) about the exact product for your application. I was using a search engine to lookup/get some basic answers to your application--To get some initial information.

-Bill

BB.

Hmmm... After a good nights sleep--I remembered why I thought that this was a transformer would be configured as a "boost" type setup (aka not a normal buck down converting transformer operating in boots step up operation).

That is because the transformer(s) is(are) energized by the 240 VAC side of your system (from utilty power) as a boost transformer. But in operation actually takes 480 VAC power from the GT Solar inverters and down converts to 240 VAC as a buck type.

And therefore, the "issue" with "reverse feed" is still there... A GT inverter cannot supply 480 VAC directly (it cannot power the transformer @ 480 VAC). So, in this case, the 240 VAC Utility side needs to initially power the transformer and provide 480 VAC to the AC inverter--And you still have the drawback of heavy starting (magnetization) surge current of running a standard buck transformer in "reverse feed".

I would still talk with a transformer engineer about your application to see what the "correct" transformer design would be for your system.

Transformers are a "loss" in the power system (say ~5% of transformer rated capacity) and it would be better to try and find a 240 VAC 3 phase capable GT inverter (lower costs, loser losses, etc.) that would not need the voltage conversion.

-Bill

dks1

BB. said:

Hmmm... After a good nights sleep--I remembered why I thought that this was a transformer would be configured as a "boost" type setup (aka not a normal buck down converting transformer operating in boots step up operation).

That is because the transformer(s) is(are) energized by the 240 VAC side of your system (from utilty power) as a boost transformer. But in operation actually takes 480 VAC power from the GT Solar inverters and down converts to 240 VAC as a buck type.

And therefore, the "issue" with "reverse feed" is still there... A GT inverter cannot supply 480 VAC directly (it cannot power the transformer @ 480 VAC). So, in this case, the 240 VAC Utility side needs to initially power the transformer and provide 480 VAC to the AC inverter--And you still have the drawback of heavy starting (magnetization) surge current of running a standard buck transformer in "reverse feed".

I would still talk with a transformer engineer about your application to see what the "correct" transformer design would be for your system.

Transformers are a "loss" in the power system (say ~5% of transformer rated capacity) and it would be better to try and find a 240 VAC 3 phase capable GT inverter (lower costs, loser losses, etc.) that would not need the voltage conversion.

-Bill

Thanks Bill!!

dks1

Thanks Bill! So the correct transformer to use is an Input of 240V & Output of 480V? 

Dax

BB.

I really cannot say... You need to contact a transformer specialist or engineer with your configuration questions.

From what little I know/understand, the "wrong" transformer (buck or step down from 480 to 240 VAC) transformer's major issue is a high surge current when first energized (vs a boost/step-up[ type transformer 240 to 480 VAC which will not have high initial surge current). Link "read more" on reverse surge current here (and other design issues):

https://cdn.shopify.com/s/files/1/2272/4275/files/Reverse_feeding_dry_types.pdf?v=1594057312

Have you looked for a set of 3 phase inverters that would work with the 240 VAC Delta wiring? It will save the transformer costs and transformer losses (losses when the sun is shining--And transformer losses when the sun is not shining).

I know enough about transformers to know that I am not the person to ask to design/size a transformer set for this application. I am OK with providing links and a bit of information--But this is not my field at all.

-Bill

PS: I would also ask the GT Inverter Mfg. and your supplier if they have any transformer recommendations.

This is something that you, personally, do not want to assume any liability for (wrong transformer, possible other power issues).

dks1

BB. said:

I really cannot say... You need to contact a transformer specialist or engineer with your configuration questions.

From what little I know/understand, the "wrong" transformer (buck or step down from 480 to 240 VAC) transformer's major issue is a high surge current when first energized (vs a boost/step-up[ type transformer 240 to 480 VAC which will not have high initial surge current). Link "read more" on reverse surge current here (and other design issues):

https://cdn.shopify.com/s/files/1/2272/4275/files/Reverse_feeding_dry_types.pdf?v=1594057312

Have you looked for a set of 3 phase inverters that would work with the 240 VAC Delta wiring? It will save the transformer costs and transformer losses (losses when the sun is shining--And transformer losses when the sun is not shining).

I know enough about transformers to know that I am not the person to ask to design/size a transformer set for this application. I am OK with providing links and a bit of information--But this is not my field at all.

-Bill

PS: I would also ask the GT Inverter Mfg. and your supplier if they have any transformer recommendations.

This is something that you, personally, do not want to assume any liability for (wrong transformer, possible other power issues).

Yes i tired getting in touch with SMA ober at Rocklin but they never fet back to my technical concers. I have however purchase a core1 33kW-US already and supplier could not guide me aswell. So i guess  i just had do online research on whoever have tried this kind of field experiment succeded or failed 😨. Now would this be possible if a step up transformer be implemented and then another stepdown in which to terminate on the line side of the building?

BB.

Now would this be possible if a step up transformer be implemented and then another stepdown in which to terminate on the line side of the building?

I am not sure I understand this question using two transformers.

Have you tried working with a transformer supplier and see if they can answer the questions?

-Bill

dks1

BB. said:

Now would this be possible if a step up transformer be implemented and then another stepdown in which to terminate on the line side of the building?

I am not sure I understand this question using two transformers.

Have you tried working with a transformer supplier and see if they can answer the questions?

-Bill

Yes talikng to a transformer supplier problem is they know nothing about solar grid tie integration.. just my luck.. anyway should  it be a succes or failure i will update this thread so others may be aware.

-dks

BB.

Just tell them it is a backup generator...

Bill

dks1

BB. said:

Just tell them it is a backup generator...

Bill

What do you mean tell my transfprmer supplier that the step up voltage is for a backup generator? Btw “Mike Holt’s Forum” has alot to say..

BB.

Step-up transformer because it is energized by the 240 VAC side first is what I have been thinking too.

The backup generator was just a suggestion to have the idea that the power flows "backwards" though the transformer... But which side is energized first (240 VAC in your case) is what defines this as a step-up transformer.

-Bill

dks1

BB. said:

Step-up transformer because it is energized by the 240 VAC side first is what I have been thinking too.

The backup generator was just a suggestion to have the idea that the power flows "backwards" though the transformer... But which side is energized first (240 VAC in your case) is what defines this as a step-up transformer.

-Bill

Thanks! However the building has a 250kVA gen set thou on an ATS. Should i terminate on the panel box where the whole load is in common with the back up generator or just on the line side from the SEC ? Can i parallel the SMA core1 with the back up generator? Or stay-out?

BB.

In general, you probably do not want the "complications" of sharing a GT inverter with a Generator.

There are issues that the generator has to have stabile enough power and frequency for the GT inverter to "qualify". And there is the issue of what happens if the GT output wattage is greater than the local AC loads. With GT>Loads, the excess power can flow backwards into the genset--And make for a very unhappy generator.

If backup genset runs seldom (few days a year), then GT Solar is not really going to save that much fuel.

If, however, you have (for example) common afternoon power outages--Then perhaps it is worth the effort to do more work and figure out if your genset+GT inverter could play together.

In any case--This is something you need to work with the generator and GT inverter manufactures to see if they could ever play together. For the SMA GT Inverter, I did not see documentation that talked about connecting with a backup genset. And I could not make out the brand/model of backup genset from your drawing.

Unless you can connect to the Inverter+Generator circuits and create an acceptable feedback path (such as the ability to reduce GT inverter output Watts to be less than the building's AC loads)--I do not think this is something that you could do on your own.

If you are still interested--I would contact the Generator Mfg and/or the local engineer that installs/maintains the genset and ask them for information.

This is way beyond anything that I can address.

-Bill