The GA3459-BL is a 20A Flyback Transformer with ferrite core and shielded flux to minimize EMI emission. This transformer is designed for the linear technology LT3751 capacitor charger controller for charging capacitors to 500V and the peak primary current drawn at minimum input voltage, DCR for the primary is with the windings connected in parallel and Leakage inductance is for one winding of the primary with the secondary winding shorted.