General Electric 9T51B0129 Buck Boost Dry Encapsulated Transformer

The 9T51B0129 Buck Boost Dry Encapsulated Transformer is a single‑phase, 0.75 kVA buck‑boost transformer with a 120/240 V primary and a 16/32 V secondary, designed to raise or lower supply voltage by small amounts in commercial or industrial circuits. It uses copper windings in a dry encapsulated core, with IS‑12 insulation, a 100 °C temperature rise, and a 180 °C insulation class, and it ships in a NEMA 3R enclosure suitable for indoor or outdoor installation. Rated for 60 Hz operation, UL and cUL listed, and identified as a Buck Boost autotransformer (frame size 12200, 1‑phase) with a dual primary/secondary configuration enabling flexible voltage combinations. The most common use is to buck (lower) or boost (raise) the supply voltage by a small amount—typically 5% to 27%—to keep devices such as lighting, controls, or small motors within tolerance.