System Integration – Future Powertrains
- Smaller volume and lower weight (higher power density)
- Shared cooling for highest performance
- Lower inductance – as low as 10 nH (measured at the IGBT pins)
- Reduced cost without sacrificing reliability
- Market readiness for transportation, distribution and alternative energy
- Scalable to any power and voltage levels
SBE is a market leader in the integration of power modules for powertrain and alternative energy inverters ranging from 50 – 500kW. SBE Power Ring technology allows for a large amount of capacitance to be placed in a small volume but often presenting a large area for connection. It allows for very low ESL if the interconnect topology is done properly. Additionally, by removing the standard packaging and coordinating the connections with the bus and IGBT module, significant weight, volume and cost can be eliminated. SBE Senior Technical Advisor and Director, Jon Bereisa, presented the values of the technology in his SAE Hybrid and EV Conference in 2012 titled “Electric Drive Cost Reduction by Design Simplification”. SBE has cultivated a team of industry partners to facilitate the entire power module integration.
The goal is to provide the maximum power density at the lowest cost. Power density is achieved by reducing the volume occupied by copper connections and device packaging (typically plastic and epoxy) to a minimum. In a typical traditional inverter installation, the space allocated to the power module is based on the connection of standard components and the need for “free air space to not cause overheating. With an optimized integration approach, as much as 50% of that total space can be reduced. A reduction in materials, including the inverter housing itself, directly improves cost with no reliability reduction.
Finally the reduction in path length from the IGBT module to the DC link capacitor and DC output allows for two important improvements:
- Elimination of “snubber caps”: snubbers occupy space, create heat, are an additional failure point and add cost
- Increase of safe, usable voltage of the selected IGBT module which provides essentially “free power” in terms of space and cost vs. a traditional de-rated design.
There are numerous approaches to integration depending on the volumetric and dimensional constraints of the system. Sometimes a very flat design is of interest, other times a cube is the most desirable. There are also circular needs (inside motor or wheel housings for example) or simply a desire to achieve world class power density and cost with a new system which has a minimum of initial physical barriers.
SBE has experience in all of these areas.
This approach minimizes the “foot print” of the module. Minimized foot print can save cost of cooling plate area and potentially inverter housing material. Additionally, many end customer platforms appreciate the vertical use of space. However, the vertical approach can be more costly depending on the input and output connection design of the inverter and can be a compromise on ESL performance ultimately limiting switch module optimization.
This approach evolves by modifying a typical powetrain inverter by utilizing the excess space left above the IGBT module (see figure 1). By bending the end of the co-planar bus plate (see figure 2), the IBGT module, cooling plate, and an SBE Power Ring capacitor are “stacked” on top of each other in a symmetrical fashion. The capacitor is placed underneath the cooling plate. The cooling plate is shared with the IGBT module which is mounted on the top.
It should also be noted that in some design examples, the “stack” is inverted with the capacitor on the top of the stack and the IGBT modules on the bottom. The resulting advantages are the same in either configuration. It is the designer’s choice which one is on the top vs. the bottom.
On figure 3, you will see that the width of the required cooling plate for both the capacitor and the IGBT modules is directly proportional to the length of the bend in this configuration. A minimum width cooling plate will reduce the ESL at the IGBT. The SBE Power Ring technology ability to provide very low heat dissipation for high ripple currents will facilitate this option.
Examples of Vertical Integration
Depending on the IGBT modules used, two Power Rings may be needed, in order to fit the available space. With this approach, there is no performance penalty vs. a single ring although the cost tends to run 15 – 20% higher due to additional manufacturing complexity. Both the single and two ring approaches are usually less expensive than traditional DC link products in the industry once full interconnects are installed. Figure 5 shows the approach of a two-ring design stacked below the IGBT.
The SBE Power Ring Module, figure 6, provides high power density at low cost for demanding power train inverters using conventional silicon or silicon carbide switching. It can be paralleled for higher power. The proven Power Ring Film Capacitor attributes of industry-leading ESL/ESR and Amps per micro-Farad can be seen in the Power Ring Module. In addition, the vertically integrated, surface mount, capacitor/bus assembly allows for maximized power density. The direct, shared cooling of the bus and IGBT provides for cost savings, size reduction and increased performance.
The Power Ring Module’s power density allows for smaller inverters while its extremely low ESL allows designers to increase operating voltages without fear of overshoot damaging the IGBT. The designer is given the ultimate in power density and system scalability.
Electrically and thermally, this approach is often the most optimized. It can use less volume than vertical integration options depending on the inverter input and output connection design. This approach can provide the lowest cost if the resulting DC link does not need a separate cooling plate and the lowest cost as it typically allows for a single Power Ring approach.
Some end-customer platforms appreciate flat, low volume designs as the search for where to “fit” additional power electronics on the platform proceeds. Depending on battery design and location often a few inches of space height can be very useful.
Additionally, the horizontal integration results in the lowest possible ESL and consequently the greatest chance for IGBT module utilization efficiency and elimination of snubbers. Should your current space be horizontally tight, you might want to start with one of our standard horizontal products as a great improvement even if not optimized. Check Power Ring Examples for options. Finally, the use of the SBE patent pending “IGBT Modules” in the hole is possible with this orientation. See the paper titled “A fully integrated 3 phase IGBT switching assembly with a very low loss DC Link Capacitor” (pdf link).
Recent horizontally-integrated SBE integrated modules include:
Development Test Kits
If you are ready to try the benefits of a SBE Integrated Module, SBE has 2 test kits (vertical or horizontal) available in stock. Simply identify the IGBT module that you are working with, the voltage and DC Link capacitance desired from the options listed in our Product Directory (pdf link). The materials used in the test kits and using the same product stress levels will often be virtually identical to the final product design. Therefore all the electrical testing and life acceleration performed on the test kit will be usable for the final design. In fact, some applications have literally “designed in” the test kit (minus the adapter plate) right into their first prototype system.
System Level Concept Animation
To view this CAD animation, click here.
Once opened, click on the
“Animations” tabulation (on left on screen), and then click on “Play”.
Circular components situated around the drive shaft are the most efficient use of space for an electric motor application. Additionally, the “coaxial” nature of the current flow, which occurs when situated this way, increases efficiency of the system and minimizes EMI (Electro Magnetic Interference) through the circular and counter flowing current paths.
Contact our application engineering team to discuss your requirements.