Operation of Power Diodes at Cryogenic Temperature

Yasmine Baazizi, Lauro Ferreira, Simon Meunier, Tanguy Phulpin, Loïc
Quéval

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Yasmine Baazizi, Lauro Ferreira, Simon Meunier, Tanguy Phulpin, Loïc Quéval. Operation of Power Diodes at Cryogenic Temperature. 3rd Momentom international congress energy at the crossroads: Accelerating innovation in the age of disruption, Mar 2023, Gif-sur-Yvette, France., 2023. hal-04055798

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Submitted on 3 Apr 2023

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Distributed under a Creative Commons Attribution 4.0 International License
# Operation of Power Diodes at Cryogenic Temperature

Yasmine Baazizi, Lauro Ferreira, Simon Meunier, Tanguy Phulpin, Loïc Quéval

Université Paris-Saclay, CentraleSupélec, CNRS, GeePs, 91192, Gif-sur-Yvette, France.
Sorbonne Université, CNRS, GeePs, 75272, Paris, France.

## Purposes

* Study the **feasibility** of a three-phase diode rectifier operating at **cryogenic temperature**.

* Electrical characterization of power diodes at cryogenic temperature.

## Converter design

<figure><img src="image_2.png" /></figure>

**Requirements :**

* AC voltage [L-L RMS] : 800 V

* Operating frequency : 50 Hz

* Nominal power : 100 kW

<caption>a) Topology #T1</caption>

VS

<caption>b) Topology #T2</caption>

<figure><img src="image_3.png" /><figcaption>Figure 1: AC/DC power supply system topologies</figcaption></figure>

## Diode characterization

* Power diodes have different electrical properties at room and cryogenic temperatures.

* Some diode technologies are more suitable for operation at cryogenic temperature.

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /><figcaption>Fig.1. Measured diode current-voltage curve</figcaption></figure>

<table><caption>Table 1. Measured diode parameters at room and cryogenic temperatures</caption><thead><tr><th>Symbol</th><th>Parameter</th><th>Temperature</th><th>BYT60-400</th><th>APT2X101_100<br>D120J_E</th></tr></thead><tbody><tr><td rowspan="2">R<sub>on</sub></td><td rowspan="2">On-state<br>resistance</td><td>77 K</td><td>10.8 mΩ</td><td>4.1 mΩ</td></tr><tr><td>~293 K</td><td>8.7 mΩ</td><td>6.0 mΩ</td></tr><tr><td rowspan="2">V<sub>to</sub></td><td rowspan="2">Threshold<br>Voltage</td><td>77 K</td><td>1.11 V</td><td>1.17 V</td></tr><tr><td>~293 K</td><td>0.82 V</td><td>1.47 V</td></tr></tbody></table>

## Models

### Thermal model

<figure><img src="image_6.png" /><figcaption>Fig.2. Thermal model</figcaption></figure>

### Current lead model

<figure><img src="image_7.png" /><figcaption>Fig.3. Current lead design</figcaption></figure>

* The losses in one current lead consist of: the heat flow into the cryostat and the heat generated by Joule effect [2],

$$dT = -\frac{dL_{cl}}{\kappa A_{cl}} \dot{Q}$$

$$d\dot{Q} = I^2 \frac{dL_{cl}}{\sigma A_{cl}}$$

* The ratio between the length and the area of the current lead is defined by the minimum heat flow,

$$\frac{L_{cl}}{A_{cl}} = \frac{\sigma}{I^2} \dot{Q}_{c,min} = \frac{1}{I} \sqrt{2\sigma\kappa(T_h - T_c)}$$

<table><caption>Table 2. Current leads parameters</caption><thead><tr><th>Symbol</th><th>Parameter</th><th>Topology #T1</th><th>Topology #T2</th></tr></thead><tbody><tr><td>R<sub>on</sub></td><td>Number and Type</td><td>2DC</td><td>3AC</td></tr><tr><td>I<sub>RMS</sub></td><td>RMS current</td><td>98 A</td><td>80 A</td></tr><tr><td>Q<sub>c,min</sub></td><td>Heat flow to the cryostat</td><td>5.26 W</td><td>4.29 W</td></tr><tr><td>L<sub>cl</sub></td><td>Length</td><td>10 cm</td><td>10 cm</td></tr><tr><td>A<sub>cl</sub></td><td>Cross sectional area</td><td>3.1 mm<sup>2</sup></td><td>2.5 mm<sup>2</sup></td></tr><tr><td>R<sub>cl</sub></td><td>Electrical Resistance</td><td>0.55 mΩ</td><td>0.67 mΩ</td></tr></tbody></table>

## Conclusion

Power diodes have different electrical characteristics at cryogenic temperatures, requiring a specific semiconductor study to select the best diode for the desired application. Operating a diode rectifier at 77 K slightly improves the system efficiency, but this efficiency is reduced if cooling power must be generated (i.e. is not "free"). The notable advantage is the potential reduction in the heatsink volume and weight by up to 90%, making it a promising solution for applications where weight is limited, such as wind power generation, aeronautical or naval transportation, especially when cooling power is freely available. The next steps are to build a prototype and test the models.

## Results

### Diode rectifier losses and efficiency

* The losses of the diode rectifier are reduced by 26% at cryogenic temperature.

* The efficiency of the diode rectifier is only improved by 0.07%.

<figure><img src="image_8.png" /><figcaption>a) Diode rectifier losses</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>b) Diode rectifier efficiency</figcaption></figure>

<caption>Fig.4. Simulated diode rectifier performances at room and cryogenic temperatures</caption>

### System losses

<figure><img src="image_10.png" /><figcaption>a) The cooling is "free" (e.g. case of future hydrogen aircraft)</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>b) The cooling is produced by a machine</figcaption></figure>

<caption>Fig.5. Comparison of the losses for each topology</caption>

### Heat sink sizing

<figure><img src="image_12.png" /><figcaption>Table 3. Heatsink sizing</figcaption></figure>

<table><thead><tr><th>Symbol</th><th>Parameter</th><th>Topology #T1</th><th>Topology #T2</th></tr></thead><tbody><tr><td>R<sub>HA</sub></td><td>Thermal Resistance</td><td>0.22 K/W</td><td>1.20 K/W</td></tr><tr><td>H<sub>length</sub></td><td>Length</td><td>0.18 m</td><td>0.07 m</td></tr><tr><td>V<sub>H</sub></td><td>Volume</td><td>4.50 L</td><td>0.42 L</td></tr><tr><td>M<sub>H</sub></td><td>Mass</td><td>0.120 kg</td><td>0.001 kg</td></tr></tbody></table>

## References

[1] A. Elwakeel, Z. Feng, N. McNeill, M. Zhang, B. Williams, W. Yuan, "Study of power devices for use in phase-leg at cryogenic temperature," *IEEE Trans. Appl. Supercond.*, vol. 31, no. 5, pp. 1–5, Aug. 2021.

[2] R. McFee, "Optimum input leads for cryogenic apparatus," *Rev. Sci. Instrum.*, vol. 30, no. 2, pp. 98–102, Feb. 1959.

The project was financed by the French government under the "Plan de Relance" and the "Programme d'investissements d'avenir".