LECTURE 34 HIGH FREQUENCY TRANSFORMER

1 LECTURE 34 HIGH FREQUENCY of Cu Wire Windings and Core WireWinding Wire Skin Effect and Multi-wireProximity Effects Alter Both Primary andSecondary R(wire coil) via Effective Acu (wire) Inductance s: Lm and Lla. Magnetizing Inductance, Lm: Core Fluxb. Leakage inductance, Ll: Air Window FluxA crude estimate for Ll is (1*Lm)/ andInterleaved Primary/Secondary Windingeffects Core Loss: Rma. Hysteresis Loss due to frictional movementb. Eddy Current Loss due to core is the TRANSFORMER Magnetization Current,im ,Created?a. im is Not effected by load current at allb. im = vLdt/Lm volt-second driven (max) of the core of a LossyTransformera. Heat Balance EquationT(core) = T(ambient) + P(core and wireloss)*R(core and Winding Structure) Inductors vs Case for Wire Losses in Transformerswith Multiple Windings ~ Number of Wire Turns, I ~ Depends onLoad Impedance in the Winding Area for the k th coil K = of PWM ConverterAK (winding) = f(PK,D), that is the winding arearequired depends on the duty cycle employed in theelectrical circuit.

transformer to take up a volume consistent with their expected power dissipation. What is not intuitively clear is that there is an optimum core flux density, B OPT, where the total of copper and core losses will be a minimum. This B OPT will guide transformer and AC inductor design. For if we hit the B OPT target we will operate with minimum

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