Introduction Context

Principles Design

Validation Example

Introduction

Context

Principles

References documents

Design

Low-Frequency Transformer (50Hz)

High-Frequency Transformer [10kHz..1MHz]

Pulse Transformer

Validation

High-Frequency Transformer [10kHz..1MHz]

This part gives some typical measurement to be conducted to verify the integrity of a power transformer. All these data should be indicated in the manufacturing specification, since definying the transformer.

Magnetising Inductance Magnetising Inductance

• Methodology
  • All other windings open and not connected.
  • Magnetic core in place.
  • Measurement of the inductance value usually in [1kHz..10kHz].
• Results and deduced parameters
  • Number of turns
    • Precision of this deduced parameter rely on the number of turns, and the precision of AL core (it can be envisaged to use a known air gapped core, or if possible to wind 10 additionnal winding on the core to measure actual AL).
  • Airgap value (presence or absence):
    • An initial measurement can be required with a known core (with known airgap) to calculate 1st the number of turns of the considered and measured winding.
  • Minimum integrity of the whole transformer:
    • Any winding being shorted in any coupled winding would be detected

Leakage Inductance Leakage Inductance

• Methodology
  • Secondary winding (the one considered) in short-circuit. (or as short as possible, or simulating the final electro-mechanical design).
  • Magnetic core in place (in some case, measurement is possible without core, depending on geometry of the windings, and their related position).
  • Measurement of the leakage inductance value usually at 10kHz (normalisation for comparison).
  • Measurement of the total resistance of the considered windings should be done from low frequency up to around 1MHz, to estimate the total (HF) copper losses
• Results and deduced parameters
  • Total leakage inductance of the windings considered, seen from "measurement" side
    • This parameter is generally used to get the switching dI/dt, duty cycle loss, frequency of expected oscillation on the rectifiers (snubber optimisation).
  • Total copper resistance of the windings considered, seen from "measurement" side
    • This parameter is crucial to calculate the total real copper losses of the transformer windings considered. A complete calculation requires a Fourrier analysis, but playing with some correction factor on the fondamental frequency resistance value is generally sufficient.

Inter-winding Capacitance

Inter-winding Dielectric Strength

Example