A Novel In-Situ Measurement Method of High-Frequency Winding Loss in Cored Inductors With Immunity Against Phase Discrepancy Error

Abstract

Evaluating the high-frequency winding loss accurately is crucial for the design of modern high-frequency power converters. This paper proposes a novel experimental method to accurately measure the in-situ inductor winding loss, which separates out the winding loss from the core loss through the reactive voltage cancellation concept. The proposed in-situ measurement can account for the complete winding loss including impacts from non-ideal field distributions by testing the inductor with the core attached, e.g., the winding edge effect, bypass flux, fringing flux, and the non-linear dynamic behaviour of the core, which cannot be well modelled with the existing analytical or simulation methods. This method has immunity against the probe phase discrepancy error, since it is designed to measure a pair of voltage and current that are in phase. This approach can be considered as the first attempt of applying the reactive voltage cancellation concept in measuring winding loss, while this concept was originally brought up for core loss and applied for core loss measurement only. By performing a Triple Pulse Test (TPT) procedure, the winding losses under practical large signals with dc-bias and rectangular voltage can be evaluated with the proposed testing circuit. The proposed approach is compared and verified against the conventional methods relying on (1) small-signal impedance measurements and FFT analysis (2) in-situ measurement with the two winding method to exclude the core loss. The presented method provides a foundation for the accurate in-situ evaluation of winding loss covering all the large-signal and non-linear effects.

In-Situ Measurement and Investigation of Winding Loss in High-Frequency Cored Transformers Under Large-Signal Condition

“…2 shows the proposed circuit for measuring the winding loss when the transformer has no load. This condition is similar to the case in an inductor presented in [22].…”

“…As an alternative, the winding loss can be indirectly measured from equation (2) through the two-winding method, which has widely been used for core loss measurement [14][15][16][17][18][19][20][21][22]. As merit, the two-winding method is simple to set up and suitable for arbitrary wave excitation for both steady-state and transient measurements.…”

“…Both the TUT and RT contain parasitics elements. However, in most cases, the leakage inductance and the winding capacitance can be assumed to be negligible and have small values [3], [6], [16], [20], [43], which do not affect the proposed winding resistance measurement [22]. Section IV will provide an experimental evaluation regarding this issue.…”

“…The TUT is excited with a bidirectional half-bridge structure presented before in previous studies [21][22], [39], [48][49]. By adjusting the output voltages of the two DC power supplies (VDC1 and VDC2), the asymmetric rectangular voltage generated by the device voltage drops can be compensated.…”

“…The proposed approach is insusceptible to the phase discrepancy error since the inductive element in the measured signals is cancelled out. While the previous work in [22] firstly applied RVC in measuring inductor winding loss, this work further extends it to transformers to investigate their winding losses considering the complications caused by the load, such as the mutual resistance and the winding-to-core field interactions under large-signal loaded condition. The proposed method is then validated and compared with the conventional measurement approaches and three-dimensional finite element analysis (FEA) results.…”