Generator
Step-Up (GSU)
Transformers

A generator already regulates its own terminal voltage through its automatic voltage regulator (AVR) and excitation system, which typically covers a ±5% range in real time. That's usually enough to handle normal grid conditions without the GSU needing to adjust taps under load. A DETC still lets you re-tap the unit during planned outages — to correct for seasonal grid voltage shifts or as the generator ages — just not while it's running. If your project's grid interconnection agreement calls for continuous on-load regulation from the transformer itself, OLTC is available as a specified option.

A delta-connected LV winding on the generator side suppresses third-harmonic currents at the source and prevents ground faults on the generator side from propagating onto the transmission network — both matter more on inverter-based wind and solar output, which carries more harmonic content than a synchronous gas or nuclear generator. The HV side stays wye-connected either way, since that's what allows effective grounding at the transmission voltage. Gas and nuclear plants, running synchronous generators with cleaner output, have more flexibility to use wye on the LV side when the plant's grounding design calls for it.

A GSU steps the generator's output up to transmission voltage and sends it to the grid. A UAT does the opposite job at a smaller scale — it steps power down from the generator bus to supply the plant's own auxiliary loads: pumps, fans, control systems, and station lighting. They're both present in most generating plants, but they're different transformers doing different jobs. LIMIK's GSU line is built for the step-up interconnection; if your project's auxiliary supply is part of the scope, talk to our engineering team about what that requires.

Yes — a GSU interconnecting a battery storage facility to the grid is engineered the same way as one serving generation, matched to the site's inverter output characteristics. Standalone storage has been independently eligible for the federal investment tax credit under IRA since the 2022 changes, separate from whether it's charged by a co-located renewable asset. LIMIK's domestic-content documentation is prepared the same way regardless of the generation type behind it — but IRA eligibility depends on your specific project structure, so confirm the details with your tax advisor before relying on it in a financial model.

Manufacturing and domestic-content records showing your unit qualifies under IRA §48 domestic content requirements, prepared alongside your standard factory test report. Exact documentation needs vary by project and by how your tax counsel is structuring the credit claim — our team coordinates directly with your compliance team to make sure what we provide matches what your filing requires.

No — they solve different problems. A GSU connects a generator to the grid and needs the electrical isolation a two-winding design provides, since a fault on one side shouldn't propagate straight to the other. An autotransformer links two transmission-level voltages that are already part of the same grounded network, where that isolation isn't required — which is why it can use a shared winding for higher efficiency. If your project is transmission-to-transmission rather than generator-to-grid, see our Autotransformers page instead.