Solar transformers

Eros

Member
Can anyone recommend a company that sells solar transformers ?
I am looking for a step down in the 115-125Kva range from 277/480v wye to 120/240v delta
thank you
 
MGM Transformers in Compton California
We buy these all the time. Be specific primary and secondary!


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Besoeker

Senior Member
Can anyone recommend a company that sells solar transformers ?
I am looking for a step down in the 115-125Kva range from 277/480v wye to 120/240v delta
thank you
To me, a transformer is just a transformer. Would there be any difference in electrical and physical specs in one where the application is say, on a water turbine rather than solar?
Just curious.
 

jaggedben

Senior Member
No you have me thinking - is there a difference between a solar and "Regular" transformer ?
No, there isn't. Although possibly a distributor that caters to solar projects might have some product selection that would be harder to find at those that don't.

BTW if your solar is the 480/277 wye and your service is the 240/120 delta then you are probably looking for a delta-to-wye 'step up' transformer. The 'primary' of the transformer you buy is the side that is intended to be connected to the utility, regardless of whether the 'secondary' is connected to a load or a source. If you want to use it 'backwards' then get approval from the manufacturer. Also the 240/120 delta is a high-leg and you are not going to connect the neutral to that side of the transformer.
 

ggunn

PE (Electrical), NABCEP certified
No, there isn't. Although possibly a distributor that caters to solar projects might have some product selection that would be harder to find at those that don't.

BTW if your solar is the 480/277 wye and your service is the 240/120 delta then you are probably looking for a delta-to-wye 'step up' transformer. The 'primary' of the transformer you buy is the side that is intended to be connected to the utility, regardless of whether the 'secondary' is connected to a load or a source. If you want to use it 'backwards' then get approval from the manufacturer. Also the 240/120 delta is a high-leg and you are not going to connect the neutral to that side of the transformer.
I'll just add that it behooves you to have a conversation with the transformer manufacturer's tech support and tell them exactly what you want to do. While the primary/secondary terminology jben describes is prevalent it isn't universal, and the tranny has to be rated to handle the current from the inverter(s) as 100% continuous.
 

GoldDigger

Moderator
Staff member
To me, a transformer is just a transformer. Would there be any difference in electrical and physical specs in one where the application is say, on a water turbine rather than solar?
Just curious.
No difference between solar and hydro in this particular scenario.
The gotcha is that generally the high voltage side goes toward the grid-interactive power source (inverter), but the startup current (surge/inrush) is supplied from the low voltage ( POCO-facing) side. Just re-purposing a simple step-down transformer with the same ratio will not necessarily work well.
And for many PV inverters, they need to see a wye connection with a grounded neutral (wye center point) even if their output power is purely line to line.
 

pv_n00b

Senior Member
Some transformers are designed to work best with current flow only in one direction. When we talk to transformer manufactures sometimes this causes PV people to get all flustered. Which side is the primary and which the secondary when current could go either direction? It gets complicated.

Specifying an MV transformer for a larger central inverter is another issue. They can have specifications for the design impedance values called out by the inverter manufacturer that need to be taken into account.
 

winnie

Senior Member
Some transformers are designed to work best with current flow only in one direction. When we talk to transformer manufactures sometimes this causes PV people to get all flustered. Which side is the primary and which the secondary when current could go either direction? It gets complicated.
One almost wants to drop the terms 'primary' and 'secondary' and instead specify:
1) which side has the voltage adjust taps which change core flux
2) which side gets energized first
3) which way does power flow

In a normal transformer, the 1) is the primary side, 2) is the primary side, and 3) power flows from primary to secondary.

However in my lab I have a transformer where the voltage adjust taps are on the secondary side (and don't change core flux; the core is just slightly oversized)

For solar use, 1) gets connected to the utility, 2) gets connected to the utility, but 3) is in the 'reverse' direction.

To the OP: what voltage are the inverters operating at and what voltage is the utility supplying? Is the utility supply balanced?

-Jon
 

mike_kilroy

Senior Member
120kva xfmr will weigh around 1000#. If you buy these often you should find close by mfgrers due to shipping cost. U do not state where u are so I cannot offer any local folks.

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beanland

Senior Member
Excitation Winding

Excitation Winding

I agree with others saying primary and secondary are dangerous words to use. The "primary" needs to be the winding that is the source of magnetic excitation of the core, the utility side. The "secondary" is the side connected to loads, even if they are negative loads like generators. This is important because the inrush will be affected by which winding provides excitation. Using a transformer in "reverse" where the nominal "secondary" is now the winding supplying excitation may lead to unpleasant surprises.

Another thing to consider is the losses. Transformers have no load losses that exist 24x7 and load losses. Over a year these may eat up 2-4% of the energy generated by the system. Select the transformer with that impact in mind. Just because it is DOE-compliant does not make it a low-loss transformer.
 
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