Battery Power - Fall 2016 - 12

Feature at slow speeds to higher-power use when accelerating or climbing steep grades. Low-inductance busbars can help achieve low-loss transfer of energy with high energy efficiency from a battery pack, by minimizing energy losses in the power transmission path from an EV's high-power battery pack to the inverter and electric drive motor. In contrast to power cables, busbars also make it possible to achieve power distribution with high power density, by mounting active components for power conversion, such as IGBT semiconductors and passive circuit elements, such as capacitors and EMI filters for noise reduction, on the busbars. In most cases, circuit elements can be incorporated onto a laminated busbar prior to its installation in an EV or HEV, or as part of the busbar's manufacturing process. Incorporating electrolytic capacitors into busbars for motor drives can improve performance while also conserving circuit volume. For further savings of space within an EV/HEV, hybrid forms of busbars are available with signal paths alongside the power planes for interconnecting, for example, current or temperature sensors and control units to on-board vehicle computers and driver controls. The ROLINX Hybrid employs either copper or aluminum conductors in various thicknesses: standard thicknesses from 0.5 to 6.0 mm for copper and from 1.0 to 5.0 mm for aluminum. For any EV/HEV application where heat is a concern, copper offers superior thermal characteristics to aluminum, with thermal conductivity of 401 W/mK for copper compared to 237 W/mK for aluminum, and thermal expansion of 16.5 ppm/K for copper compared to 23.1 ppm/K for aluminum. Aluminum busbars are attractive for EV/HEV applications because they provide reliable electrical performance while helping to save total system weight, since aluminum busbars are typically 50 percent lighter than copper busbars. For equivalent electrical/thermal performance, however, the cross section of an aluminum busbar will be greater than that of a copper busbar with, for example, a 1 mm copper conductor replacing a 2 mm aluminum conductor. For EV/ HEV applications, copper busbars offer excellent solutions where space is tight, while aluminum busbars, enable efficient energy distribution with weight savings compared to copper. Aluminum is also less costly than copper. Design Considerations Figure 2. The ROLINX Hybrid is an example of a commercial laminated busbar that combines signal and power connections to save space in the design of an EV or HEV. Performance Limits Understanding the performance limits of a laminated busbar can help guide optimum use of these components for power distribution in EVs and HEVs. As an example, the ROLINX Hybrid from Rogers Corp., Power Electronics Solutions is a laminated busbar that combines power and signal paths in a compact assembly (Figure 2) suitable for power distribution and signal connections within and from the large rechargeable battery pack in an EV/HEV. In addition to power-handling capabilities that equal or surpass those of shielded cables, the low-inductance busbar provides signal and ground planes for mounting and connection of additional components, including electrolytic capacitors and surface-mount-technology (SMT) components, such as EMI/RFI filters for noise reduction within a vehicle's power distribution system. As noted earlier, busbar performance will depend upon the composite materials used to construct the busbar. 12 Battery Power * Fall 2016 In the design of the conductors for any busbar, the ground return conductor should be at least as large in area as the voltage conductor. This serves to improve the capacitance of the busbar and also provides a sufficiently large ground plane for thermal dissipation and to minimize voltage variations due to temperature effects. An adequate busbar ground plane can also help to limit coupling effects from nearby electronic circuits and components in an EV/ HEV. Insulation/dielectric materials used in the construction of busbars for EVs and HEVs are as important as its conductor materials. Insulation should exhibit stable dielectric constant with temperature so that the resulting capacitance and voltage through a busbar remains stable with temperature. Higher busbar capacitance translates into lower impedance and better rejection of noise, and can be achieved by using thinner dielectric layers between a busbar's conductive layers. Insulation is used on both the outside and inside of a sealed busbar construction, with a variety of insulation materials applied, including flexible polyester films (for highervoltage, lower temperature applications) and polyimide films (for higher-temperature, lower-voltage applications). Inner insulation often includes some form of filler for increased insulation and rigidity, such as glass fiber or cloth (Figure 3). When required, busbars can be sealed by means of edge insulation, typically by means of mold or potting. Specifying Busbars for EV/HEVs Specifying a laminated busbar for an EV/HEV or other application requires an understanding of certain minimum dimensions, including the form factor for a particular EV or www.BatteryPowerOnline.com http://www.BatteryPowerOnline.com

Table of Contents for the Digital Edition of Battery Power - Fall 2016

Improving Lithium-Ion Battery for Future Energy Storage Needs
Protecting Lithium Batteries and Battery Packs from Runaway Thermal Events
Sorting Busbar Choices for Electric Vehicle Power Distribution
2016 Battery Power Resource Guide
Battery Power - Fall 2016 - Cover1
Battery Power - Fall 2016 - Cover2
Battery Power - Fall 2016 - 3
Battery Power - Fall 2016 - Improving Lithium-Ion Battery for Future Energy Storage Needs
Battery Power - Fall 2016 - 5
Battery Power - Fall 2016 - 6
Battery Power - Fall 2016 - 7
Battery Power - Fall 2016 - Protecting Lithium Batteries and Battery Packs from Runaway Thermal Events
Battery Power - Fall 2016 - 9
Battery Power - Fall 2016 - Sorting Busbar Choices for Electric Vehicle Power Distribution
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Battery Power - Fall 2016 - 2016 Battery Power Resource Guide
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