What inverter is appropriate for a 10kW high-leg delta solar application?

Hello,

I'm working on a 9.2kW project with a MecaSolar tracker. I have concerns as to the appropriate inverter for the application and I was wondering if you could point me in the right direction. The application's power pole/utility intertie is a Delta, 2 hv, 2 pot, three phase/4 wire system. So, across the legs, 240/240/240 with a high/red leg. Here's the link to show an example... http://en.wikipedia.org/wiki/File:High_leg_delta.svg.

Since the SMA 10kW is designed for three-phase delta 208V applications, I'm not sure that this inverter would be appropriate. Seems as though this would be an unbalanced load across the legs.

The SMA 5-8kW units have the ability to set all three phase legs separately. The grid is an open/stinger/red leg Delta three phase for an irrigation pump. Basically across the hot legs the voltage is 240, but testing legs to neutral, one leg measures 277. It would be an unbalanced load. Instead of the 10kW, probably use two SB5000 units?

Thanks!

Comments

How is the pump connected? Can you duplicate that using one or two inverters?

Treat this service very carefully. I have seen it send many frequency drives and servo amps to an early grave. If the inverter was configured for a Wye transformation I am pretty sure it would be a fatal encounter for the inverter to be connected to the Delta service without a transformer. Also double check your "high" leg. It should be closer to 208 than 277. The neutral connection on this service is a middle tap on one of the single phase transformers. Usually it is the B phase that is the high leg although it can be found on the C phase in some metering cabinets. NEC requires it be marked with orange tape or equal. I am looking for more info and will follow up.

It's hard to find small 3 phase inverters so you have two easy choices. One is to go with two 240V inverters around 4 to 5kW each and put them across any two phases. The other is to go with three 240V inverters around 3kw each and put one on each phase. As long as the inverters can be installed without connecting a neutral you don't have to worry about the high leg.
Make sure you check with the utility to find out how much phase imbalance they allow for PV systems. Most will allow up to 6kW which should be fine as long as you don't try to install just one inverter.

Power One has a 10kW 3 phase inverter that might be worth looking at.

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Submitted

12 years 11 months ago

Asked by

Doug Fischer

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