Outdoor photovoltaic isolation transformers are step-up isolation transformers, which are generally used for solar inverters. Because the photovoltaic transformer itself has low photoelectric efficiency, the efficiency of the transformer is particularly required. The three-phase photovoltaic isolation transformer not only has the function of voltage transformation in the power grid, but also can isolate the third harmonic of the grid to the equipment. The primary and secondary are shielded by copper foil, which effectively protects the interference of the grid harmonics to the equipment. Photovoltaic grid-connected inverter isolation transformer grid-side wiring dyn11, yd5 during inverter, phase shift 120 degrees, photovoltaic isolation transformer can be set to work during the day and stop at night to reduce no-load power loss.