SiC Power Modules in 200kW Three-Phase Inverter Reference DesignJanuary 28, 2020 by Paul Shepard
The CRD200DA12E-XM3 200kW three-phase inverter reference design from Wolfspeed demonstrates best-in-class system-level power density and efficiency obtained by using Wolfspeed's new XM3 power module platform. The XM3 modules feature Wolfspeed C3M SiC MOSFETs in a low-inductance (6.7nH), high power density module package capable of 175°C maximum junction temperature operation, which simplifies the overall system design.
This reference design also features an optimized laminated bussing which reduces total power loop inductance and a high-performance liquid cool plate to maximize power dissipation. System controller and sensors are included to allow designers to quickly evaluate the XM3 module's performance in applications such as motor and traction drives, grid-tied distributed generation, uninterruptible power supplies, energy storage systems, and other high-frequency, high-efficiency power conversion designs.
To take advantage of the low-inductance power module, the remaining power components of the inverter's dc side must be designed to minimize stray inductance. Lower power loop inductance results in lower peak overshoot voltages seen by the switches as well as reduction in ringing and oscillation.
A complete low-inductance structure therefore enables faster turn-on and turn-off times and thereby lowers switching losses. The design philosophy for the inverter directly follows the design philosophy utilized in the SM3 module: maximize performance through high-ampacity, low-inductance designs while minimizing cost and complexity. To achieve this, 5 key parameters were considered:
- First, due to the high current density achieved through SiC devices and the compact module size, a high-performance thermal system must be implemented to maximize heat transfer.
- Second, the stray inductance introduced by the busbar structure should be minimized through the use of low-inductance, overlapping planar structures.
- Third, to closes the high-frequency switching loop effectively, low-inductance and high ripple rated capacitors must be utilized.
- Fourth, optimal device control with high-speed protections and high noise immunity must be utilized in the gate driver to effectively switch the devices and provide maximum survivability under fault conditions.
- Fifth, the entire structure's cost should be minimized and the entire inverter structure should be engineered to minimize complexity for assembly and manufacturing.
The resulting inverter measures 279mm x 291mm x 115mm for a total volume of 9.3 liters and a power density of up to 32.25kW/L, more than twice that of comparable silicon-based inverters. Compared to Wolspeed's previous 250kW, 1.2kV 3-phase inverter, this design offers about a 65% reduction in volume and about a 340% increase in power density.