Laminated busbars: what are they and how are they used?
Busbars have long been dubbed as the “backbone” of majority of power applications today. They serve as vital interfaces between the power module and its electronic environment. It should come as no surprise, therefore, that busbars are also being used with electric vehicle batteries.
As electricity is being generated by the EV batteries, busbars function by distributing the current flows between the elements within an EV’s systems and sub-systems. What is key here is efficient power conduction throughout the entire electric vehicle, which busbars can deliver. Of course, busbars are not just limited to their electrical functions; the structure of the busbars within the vehicle is equally important especially in the presence of form constraints and in thermal management, particularly effective heat dissipation.
For this article, we focus specifically on laminated busbars – what they are, the advantages that can be derived from their use, and a brief comparison with another busbar type, the flexible busbar.
What are laminated busbars?
Laminated busbars are the end products produced from the assembly of multiple layers of conductive metals – copper or aluminum, in particular. These metal layers are separated by paper-thin layers of dielectric material. Heating and compressive processes are applied to these layers to form a rigid, integrated component which is connected with a platoon.
Laminated busbars may come in specific forms, such as strips, solid rods, bars, or tubes. These shapes are based upon the current and performance requirements in which the busbar will be used. Because of the increasing compactness and complexity of new-generation applications, like those found in EV batteries, laminated busbars provide improved attachments to these applications with the use of specialized connectors (such as the Interplex BusMate power busbar connector), without using traditional assembly processes, such as soldering, welding, bolting, or clamping.
How are laminated busbars used?
In an electric vehicle, laminated busbars essentially function by serving as conductors to power-generating components within the EV electrical system. They transfer the electrical energy that is produced from the EV batteries to the EV’s inverter. This energy is then converted into AC electricity which powers the electric drive motor and other sub-systems.
Because of the laminated busbar design, it is possible to have power distribution with a high-power density. This can be achieved by mounting directly on the busbar active components for high-power conversion, including IGBT semiconductors, and passive circuit elements like capacitors and EMI noise reduction filters. All of these components help to improve driving range and performance while, at the same time, conserving the volume of circuits.
As was mentioned earlier, laminated busbars can also be used for thermal management in an EV. While AC drive motors actually dissipate little heat, heat generation is actually greatest along resistive junctions where the current flows in the EV’s power distribution system.
The use of copper or aluminum, which are good thermal conductors, enable busbars to serve as part of an EV’s thermal path, with heat being diverted from the heat source to a heat sink or coolant reservoir.
Benefits of using laminated busbars
There are a number of benefits to using laminated busbars together with EV batteries.
For one, laminated busbars offer IMPROVED RELIABILITY. Traditional busbars are complicated because of the many interconnected parts and cables that take too much time to assemble. Aside from the time-consuming assembly, the components and cables are subjected to detrimental factors in their operating environments, such as vibration and heat.
Not only is there an increased risk for installation error, there may also be instances of vibration failure along the assembly points. In contrast to traditional busbars, laminated busbars have been pre-assembled with all the internal components fused into its frame, forming a sturdy and compact structure. There is very little risk for wiring errors or vibration failures.
Another benefit of laminated busbars is LOW HEAT DISSIPATION. This was discussed in full in the previous section. The conductive materials in the busbars are in the right amounts to carry low- or high-power densities. These busbars not only result in low heat generation, but they are also capable of delivering the excess heat to heat sinks or coolant reservoirs to maintain the right temperature in the EV’s various sub-systems.
LOW INDUCTANCE is another benefit that can be derived from laminated busbars. Here is a simple explanation of what inductance is. The flow of electrical power through conductive material causes the creation of an electromagnetic field. This is inductance. In the presence of stray inductance in an EV, it causes interference in the car’s electronics, overheating, and ultimately system failure.
The layered charged conductors in the laminated busbar plus the insulating dielectric material in between each layer results in the cancellation of the electromagnetic fields – and inductance – that develops. This means a more efficient conduction system. It certainly is no wonder that laminated busbars are the best choices for very sensitive and critical EV power systems and sub-systems.
INCREASED CAPACITANCE is yet another laminated busbar benefit. As the conductive materials work to cancel out inductance, on the other hand, they increase the busbar’s capacitance or its ability to store electrical energy in the EV battery.
Of course, the LAMINATED BUSBAR DESIGN is in itself a benefit because of its guaranteed improved structural integrity and flexibility and reduced service costs. We have discussed earlier how the structure of the busbar does not leave any room for potential connection errors and failures, in comparison with traditional busbars. It is also flexible, allowing for customizations that meet the specifications of the power applications in which it will be used. Last but not least, with a lower assembly time, you also reduce service costs in production and maintenance of the busbar.
Applications for laminated busbars
Versality of laminated busbars has made them popular in a wide variety of industries and applications. Again, busbar design is customized to meet power application specifications.
You can find laminated busbars being used extensively in the following applications:
- Automotive and Transportation – Electric and hybrid vehicles, power and hybrid traction systems
- Manufacturing and Industrial – Factories, motor drives, welding systems
- Energy – Power generation and conversion systems and equipment, power switch systems
- Datacom and Telecom – Communication base stations, cellular communications, telephone exchange systems, network servers, data storage systems, supercomputers
- Aerospace – Aircraft, military, and defense electronics
Laminated vs flexible busbars: what’s the difference?
Finally, when it comes to busbar design in EV batteries, you may have heard of flexible busbars being recommended just as often as laminated busbars.
The main similarity between laminated busbars and flexible busbars is that they are both multi-layered. However, while laminated busbars are sturdy and rigid structures, the same cannot be said for flexible busbars.
Flexible busbars are made out of layers of copper foils which are tightly attached to mounting areas, using a process called diffusion welding. While the ends are rigid to enable connections, the middle of the busbar is kept flexible.
Laminated busbars are customized during manufacturing to meet power and space constraints. Flexible busbars are just as customizable as their counterparts, but their greater flexibility means that they can fit in small, tight, or curved spaces without compromising mounting strength. Their flexibility also means that these busbars provide greater shock and vibration absorption.
Laminated busbars and flexible busbars are at the forefront of a revolution of busbar technologies with new and improved capabilities. Not only can these technologies guarantee improved driving performance in electric vehicles, but they can also be applied in various applications where efficient and safe electrical conduction is required.