50kW GaNインバータの開発

Development of 50kW GaN Inverter


GaN power devices, as the next generation power semiconductor devices, are expected to provide high-speed switching with low-loss performance characteristics. As improvements in loss performance are being promoted, heat dissipation design has become a major issue. Low-loss performance means that a large current can flow in a small device cross-sectional area; however, this dictates that the heat dissipation cross-sectional area must also be small. Therefore, effectively cooling the device is a technical challenge to maximize the device performance.

本プロジェクトでは、厚銅基板を銅バスバーとした放熱構造設計を行い、小さくても高出力なGaNモジュール基板を構成しました。 GaNモジュールを積層することにより、インバータモジュールを構成します。モジュールは水冷冷却を行うことで、GaNデバイスのパフォーマンスを引き出すことができます。今回、GaNインバータモジュールを3個使用することで、50kWの大出力インバータを実現しています。

In this project, we designed a heat-dissipating structure using thick copper substrates as copper busbars to construct small but high-power GaN module substrates. An inverter module was formed by stacking GaN modules. The modules are water-cooled to achieve the exceptional performance of the GaN devices. A high output inverter of 50 kW is realized using three GaN inverter modules.

50kW GaNインバータ
50kW GaNインバータ
50kW GaN inverter
GaN Device Multi-Parallel Mounting Unit


Bench evaluation of GaN inverters


We have been evaluating actual motors with GaN inverters and other devices. On the motor evaluation bench, we measure the input/output characteristics of the inverter and motor, adjust various control parameters, such as inverter output current, switching frequency, and dead time, and evaluate the efficiency of the inverter and motor. This fiscal year, a large motor bench will be installed to improve the evaluation environment.

50kW GaNインバータ
Motor Evaluation Bench


Motor Control Research


Motor losses are broadly classified into iron loss and copper loss. High frequency operation of GaN inverters reduces iron losses, but not copper losses. To optimize motor drive operation with GaN inverters, these motor losses must be evaluated separately. However, since only a mixture of the two losses can be measured on the motor bench, motor electromagnetic simulation must be performed. We have built an electromagnetic simulation environment that models motors in detail and evaluates the breakdown of motor losses against the output current ripple in the inverter. It has been found that GaN inverters can suppress the temperature rise of motors and increase power density by reducing losses. This is expected to increase the efficiency of EV drive systems and reduce CO2 emissions.

モーターの電磁界シミュレーション モーターの電磁界シミュレーション
Electromagnetic simulation of motors