Investigation of Transformer Winding Architectures for High-Voltage (2.5 kV) Capacitor Charging and Discharging Applications

Abstract

Transformer parasitics such as leakage inductance and self-capacitance are rarely calculated in advance during the design phase, because of the complexity and huge analytical error margins caused by practical winding implementation issues. Thus, choosing one transformer architecture over another for a given design is usually based on experience, or a trial and error approach. This paper presents analytical expressions for calculating leakage inductance, self-capacitance and ac resistance in transformer winding architectures (TWAs), ranging from the common non-interleaved primary/secondary winding architecture, to an interleaved, sectionalized, and bank winded architecture. The calculated results are evaluated experimentally, and through finite element (FEM) simulations, for a RM8 transformer with a turns ratio of 10. The four TWAs such as, noninterleaved and non-sectioned, non-interleaved and sectioned, interleaved and non-sectioned, and interleaved and sectioned, for an EF25 transformer with a turns ratio of 20, are investigated and practically implemented. The best TWA for a RM8 transformer in a high-voltage (HV) bidirectional flyback converter, used to drive an electro active polymer based incremental actuator, is identified based on the losses caused by the transformer parasitics. For an EF25 transformer, the best TWA is chosen according to whether electromagnetic interference (EMI) due to the transformer interwinding capacitance, is a major problem or not.

Digital Control of a High-Voltage (2.5 kV) Bidirectional DC--DC Flyback Converter for Driving a Capacitive Incremental Actuator

“…Since, the MOSFET capacitance cannot be eliminated, the only way to reduce the capacitive switching loss is by reducing both the leakage inductance and self-capacitance of the transformer. In [16], several transformer winding architectures (TWAs) are proposed especially for HV capacitor charge and discharge application. The TWA can be selected depending on the application where the actuator is used.…”

“…Selecting a best transformer winding architecture (TWA) and optimizing the HV transformer using it, would lead to an improved energy efficiency. Several TWAs for HV capacitor charge and discharge applications, have been investigated and implemented in [16], with turns ratios 10 and 20, respectively. In [17] an efficiency optimization technique is proposed for a bidirectional flyback converter used to a drive a HV capacitor load.…”

An Improved Stray Capacitance Model for Inductors

“…Secondly, plot all possible groups of (p, ) in the two-dimensional design map. The global minimum capacitance point is therefore obtained with the width and heigh restriction (26,27), as illustrated in Fig. 12.…”

“…d) How to optimize the winding design in terms of its capacitance and ac resistance? Compared with the ac resistance optimization [23][24][25][26], there is not much research on the optimization of winding capacitance, as it is usually performed by changing the layer insulation distance directly or employing different winding structures [1,27]. A systematic method to reduce or control the total capacitance for the winding optimization is still missing.…”

New Incremental Actuators Based on Electroactive Polymer: Conceptual, Control, and Driver Design Considerations

“…In [34] an efficiency optimization technique is proposed for a bidirectional flyback converter. Several high voltage transformer winding architectures (TWAs) have been investigated in [35]. Control algorithms for optimal-flyback charging of a capacitive load have been proposed in [36], which focuses mainly on minimizing the conduction losses in the converter.…”