What Are the Forms of Busbars in New Energy Vehicles?

Do you know about busbars in the new energy industry? Copper busbar, aluminum bar, copper-aluminum composite bar; hard bars, flexible bars, flexible-hard transition bars; flexible-hard copper busbar welding, etc.

What is a busbar?

What exactly is a busbar? A busbar is used to electrically connect battery cells and realize the series or parallel structure of cells. It also performs voltage and temperature sampling, playing a crucial role in the safety of power batteries.

Busbars in new energy vehicles are a type of multilayer composite structure connection busbar:

• Connection mode: Busbar connection is achieved by welding or bolting battery terminals or module poles in series or parallel.
  

• Applications: Besides being used in new energy vehicles, composite busbars are also widely used in power and hybrid traction equipment, power traction equipment, cellular communications, base stations, telephone exchange systems, large network equipment, medium and large computers, power switch systems, welding systems, military equipment systems, power generation systems, and power conversion modules of electrical equipment.
  

Classification of busbars

What are the types of busbars?

Busbars for new energy vehicle battery packs and energy storage battery systems, copper-aluminum structural components

Classified by material: ① copper, ② aluminum, ③ copper-aluminum composite;

Classified by processing characteristics: ① hard busbar, ② flexible busbar, ③ flexible-hard transition busbar.

Welding equipment needed for busbar production

Producing busbars involves a full-process workflow, including cutting, pre-positioning (partially needed), diffusion welding, stamping, polishing, bending, heat shrinking (partially needed), inspection, packaging, and shipping.

The most critical step is the welding stage. The standalone welding machines for busbars include: high polymer diffusion welder, copper foil flexible connection diffusion welder, and aluminum foil flexible connection diffusion welder.

Copper bars, also known as cubicles or current-carrying bars, not only have a beautiful metallic luster in appearance but also demonstrate significant internal strength!

They possess high mechanical performance, excellent electrical conductivity, good thermal conductivity, corrosion resistance, electroplating properties, brazing properties, easy forming, and processing performance... These numerous advantages make them widely used in power transmission and transformation, electrical equipment, and various other fields.

Types of copper bars

By section

By section, they are divided into rectangular, circular, D-shaped, U-shaped, among others. Rectangular copper bars are most widely used in voltage levels of 40.5kV and below due to smaller resistance, larger heat dissipation surface, and higher current capacity compared to circular, D-shaped, and U-shaped busbars.

Circular and D-shaped copper bars are also used due to better skin effect and anti-corona performance, although the connections are more complex.

U-shaped copper bars are generally used in devices with high current and high mechanical effect requirements, such as generator outlet switch cabinets. Their rated current is large, generally reaching above 5000A, and the rated peak withstand current (IP) is generally above 50KA.

By natural state

By natural state, copper bars can be classified as hard copper bars (TMY) and flexible copper bars (TMR). Flexible copper bars are mainly used in locations where connections are inconvenient and can absorb some mechanical effects, such as inside circuit breakers.

(Image: Flexible copper bars)

What affects the current capacity of copper bars?

Firstly, we need to understand that in addition to the size of the copper bar's section, environmental temperature and placement methods are also main factors affecting current carrying capacity.

Environmental temperature

Environmental temperatures are mainly in 25℃, 30℃, 35℃, and 40℃. The temperature for the location with the highest average temperature in the hottest month is used as the reference for selecting the environment temperature. Since the resistance of conventional conductors is directly proportional to temperature, the higher the temperature, the greater the conductor resistance, which inevitably reduces current carrying capacity. Therefore, different temperatures result in different current capacities, and it's best to choose locations with good ventilation for installation.

Placement method

The current capacity of a single busbar placed vertically in the same environmental temperature is indeed higher than when laid flat. Data indicates that when the width of a single copper bar is ≤63mm, the current capacity when placed horizontally is 0.95 times that when placed vertically. When the width is >63mm, it's 0.92 times that when placed vertically.

This is because vertical placement accelerates air convection, allowing the heat of the copper bar to dissipate quicker. In contrast, horizontal placement slows air convection, causing slower heat dissipation, thus affecting the current capacity.

For better heat dissipation, when paralleling two or more rectangular copper bars, the gap between parallel copper bars should not be less than the thickness of the copper bar.

Methods to estimate the current carrying capacity of copper bars

Many people find it troublesome to estimate the current capacity of copper bars and often refer to manuals. Today, Xiao Nan will provide a high-efficiency and straightforward method to estimate the current capacity of copper bars. Here's the estimation formula:

Single bar = Width (mm) × Thickness coefficient

Double/Triple/Quad bar = Width (mm) × Thickness coefficient × Experience coefficient

However, it is better to use special-shaped busbars if reaching four bars.

(Image: Coefficient reference table)

Next, take the example of a hard copper bar (TMY) with a width of 100mm × 10mm thickness, placed vertically at 40℃:

Single bar=100×18.5=1850(A) [Manual: 1870A]

Double bar=(100×18.5)×1.58=2923(A) [Manual: 2970A]

Triple bar=(100×18.5)×2=3700(A) [Manual: 3750A]

(Image: Tin-plated copper bar)

Additionally, there's a very simple formula to calculate the current capacity of copper bars at 40℃:

Single rectangular current capacity of copper bar= Width × (Thickness + 8.5) A

For example:

15×3 current capacity=15×11.5=172.5A

100×8 current capacity=100×16.5=1650A

Double layer current capacity = 1.5 times single layer current capacity

Triple layer current capacity = 2.0 times single layer current capacity

Jintian Copper as a copper busbar manufacturer has accumulated rich experience and technical strength in copper material production, committed to providing high-quality copper busbar products for power, communication, and other industries. With advanced production processes and strict quality control, Jintian Copper enjoys a good reputation and credibility in the industry.