TM50A is a mid-high-frequency high-permeability MnZn power ferrite with an initial permeability (μi) of 2500, the highest among the mid-high- and high-frequency power grades, a saturation flux density (Bs) of 550 mT at 25 °C (450 mT at 100 °C) and a Curie temperature above 240 °C. Before the introduction of TM59 it was the grade with the lowest hot-state loss at 500 kHz / 100 mT (800 → 700 kW/m³) and, together with its high μi and 450 mT hot-state Bs, the principal material for 300–500 kHz LLC main transformers and resonant inductors; at 500 kHz / 50 mT it reads 120 → 100 kW/m³ and at 1 MHz / 30 mT 210 → 150 kW/m³, so its effective upper frequency is about 500 kHz. Of the two mid-high-frequency grades TM50A is the earlier generation: TM59 is recommended for new designs (600 → 550 kW/m³ at the same operating point, lower Br and higher DC-bias capability at 100 °C); TM50A remains in supply for existing designs and remains appropriate where μi 2500 is required to reduce the number of turns. At 300 kHz / 100 mT the loss rises from 150 kW/m³ at 25 °C to 280 kW/m³ at 100 °C, so the thermal design should be evaluated at the hot-state value.