Most people consider the selection of a busbar material (copper/aluminum), busbar current rating, and busbar insulation when designing an electrical distribution system. However, one important factor that is sometimes forgotten is the busbar joint.

A busbar is only as reliable as its joints. A copper or aluminum busbar in perfect shape could still cause overheating, voltage drops, or a system failure if the jointing technique is wrong for the application.

There are many jointing techniques available for busbars, but the two most common today are bolted and welded. Each has its own pros and cons and is best suited to different applications and circumstances.

If you are involved in manufacturing switchgear, designing electrical panels, working on power distribution projects, installing EV charging stations, or manufacturing industrial equipment, having an understanding of these jointing methods will enable you to make more informed decisions with regard to your long-term performance of your systems.

What is Busbar Joint?

The connection where two or more busbars are physically & electronically connected to create an unbroken path to allow current to flow through them is called a “busbar joint.”

The busbar joint is primarily used to:

• Provide low electrical resistance

• Provide reliable current transfer

• Limit the generation of heat

• Provide mechanical stability

• Provide long-term safe operation

The overall success of the entire power distribution system is based on the design and installation of the busbar joints.

What is a Bolted Busbar Connection?

A bolted busbar connection consists of two busbars being connected by the use of bolts, nuts, washers, and contact surfaces that are tightened against each other to create both electrical and mechanical continuity.

Nowadays, bolted busbar connections are widely used in modern switchboards, distribution, transformer connections, and electrical control systems due to their adaptability and ease of maintenance.

How it Works

When two busbars come into contact with one another, they are compressed using high-tensile-strength bolts. The amount of torque on the bolts creates sufficient pressure to allow for an excellent contact surface, therefore maintaining an acceptable amount of electrical resistance between the two conductive pieces.

Typical Applications

• Switchgear Assemblies

• Power Distribution Panels

• Motor Control Center Panels

• Low Voltage and Medium Voltage Electrical Systems

• Transformer Bus Duct Systems

• Electric Vehicle Charger Busbar Assemblies

• Industrial Control Panels

Advantages of Bolted Busbar Connections

Quick Assembly

Components can be assembled without the need for special tools to perform welding operations.

Ease of Service

The component will be easy to remove or replace if required without damaging the busbar.

Flexibility to Expand

Additional sections to the installation can be added at any time, making bolted joints ideal for future expansions.

Lower Initial Costs

Labor costs associated with the installation of bolted connections tend to be lower than those of a welded connection since there is no requirement for welding processes, specialized equipment, or skilled labor.

Appropriate for Large-Scale Applications

When working with extensive busbar installations, bolted connections offer a simpler method of installation and modification in the future.

Disadvantages of Bolted Connections

Loosening Over Time

In the presence of heat and vibration (e.g., fail-safe applications), excess torque can be lost, and the force with which the busbars are clamped may decrease over time.

Higher Resistance to Current Flow

As compared to properly welded connections, bolted connections will generally provide a slightly lower degree of conductivity due to the relative size of the contact area of the joint compared to that of a welded joint (properly welded connections will create a larger area for electrical conductivity because the surfaces will be evenly distributed throughout the joint area).

Requirement for Periodic Inspection

Most installations require periodic inspection and maintenance if bolted connections are used.

What Is a Welded Busbar Connection?

A welding connection is one where two or more busbars are joined by permanently melting them together so that they become one unit. The result of this process is that you now have an uninterrupted conductive path for electricity to flow through, creating an electrically continuous conductor connection from one busbar to another.

Therefore, the use of a welded connection is the most dependable and efficiently conductive way to join conductors for electrical purposes.

An Overview of Welding Busbar Connections

When welding is performed on two pieces of metal, the metal will be heated sufficiently to cause a molten puddle to form, and once this molten puddle becomes solid, it can join the two pieces of metal into one continuous piece.

Examples of common types of metal welding are the following:

• TIG welding

• MIG welding

• Resistance welding

• Specialized applications utilizing brazing

Thus, making it so that there is now a complete continuous electrical conductor connection between both busbars.

Applications of Welded Busbars

• High-current industrial power

• Power generation facilities

• Battery storage systems

• Rail transport

• Renewable energy projects

• Specialty electrical equipment

• Permanent busbar assemblies

Benefits of Welded Busbar Connections

Minimal Resistance

Welded connections typically don’t form mechanical interfaces  therefore, they have the best electrical conductivity among all connection types.

Permanent Joint Integrity

Once made properly, the joint will not come loose.

Compact Design

Welded connections are frequently installed with less space than bolted-to-transitory-type hardware connections.

Vibration Resistant

If even when an application experiences significant vibration, welds are typically preferred.

Improved Distribution of Current Flow

By creating one continuous connection piece, welded connections will provide more uniform electrical current flow than any other type of joint.

Limitations of Welded Busbar Connections

Difficult to Change

Almost all new modifications require cutting of existing busbars, which adds time and labor costs.

Increased Level of Installation Complexity

Special equipment and qualified welders are needed to connect the busbars using welding.

Longer Duration for Repair

When there is a defect, repairs are usually much more time-consuming than they would be if the busbars were bolted together.

Heat-Affected Zones

Welding improperly can alter the material properties and reduce the performance of the busbar.

Comparison of Busbars Connected by Welding vs. Connecting by Bolting

Which Is the Best Type of Busbar Connection: A Welded vs. A Bolted Connection?

When discussing busbars, there is no definitive winner between welded connections and bolted connections therefore, they each possess different advantages depending on the application. When more emphasis is placed on aspects such as maintenance, flexibility, and future growth, it is generally preferable to use bolted busbars. However, when using welded busbars, you are creating a more permanent bond that is optimized for high-current applications where maximum electrical conductivity is necessary as well.

Top Benefits of Proper Busbar Jointing 

Regardless of the Method Employed. Below you will find a list of advantages associated with using well-engineered busbars:

• Reduced energy losses

• Lower operating temperatures

• Improved system reliability

• Better electrical efficiency

• Enhanced safety performance

• Longer equipment lifespan

• Reduced maintenance costs 

Common Causes for Busbar Connection Failure

Most failures associated with busbars happen due to installation mistakes rather than manufacturing defects.

1) Incorrect Torque Settings:

 If you are not tightening the joint correctly, your chances of experiencing excessive resistance are great. Conversely, if you over-tighten the connection, the likelihood that you will damage the conductor is also significant.

2) Poor Surface Preparation:

 Any oxidation, dirt, and/or contamination can create resistance at the physical connection between the two metal surfaces.

3) Mixing Dissimilar Materials:

When connecting copper and aluminium conductors, specially designed transition components and sleeved aluminum busbars solutions can help minimize galvanic corrosion and improve long-term reliability

4) Inferior Fasteners:

Using inferior fastener hardware may lead to loosening or failure due to thermal cycles (heating and expanding).

5) Neglecting for Thermal Expansion: 

When designing large-scale bus bar systems, consideration should always be given to the effects of expansion and contraction.

How to Maintain Reliability of Bus Bars Over Their Life Span

Here are some reliable tips based on real-world experience that will enhance the performance of your busbar joints:

Use Tin-Coated Contact Surfaces

Many industries prefer products from a reliable tin plated copper busbar manufacturer because tin-plated contact surfaces help reduce oxidation and improve long-term conductivity. Proper surface protection significantly enhances joint performance and reduces maintenance requirements.

Adhere to Manufacturer’s Full Load Torque Specifications

Never guess at the torque value needed for an installation always refer to the manufacturer’s specifications for the correct torque value.

Perform Thermal Imaging Inspections

Thermal imaging inspections performed on a periodic basis can detect hot spots in advance of failure.

Select the Right Type of Joint Based on the Environment

The environment in which the joint will be used should influence the type of joint selected to minimize vibrations, moisture, temperature, access for maintenance, etc.

Work with Reputable Busbar Manufacturers

Most custom-fabricated busbars will require specially designed joints for the specific application in order to produce the best performance.

Selecting Between Bolted and Welded Connections for Busbars

When selecting between bolted or welded connections, it is more important that the selection be based on the application as opposed to aesthetics.

Consider the following reasons to utilize bolted connections:

Choose bolted busbar connections when:

• Future modifications are expected
• Easy maintenance is required
• Large distribution systems are involved
• Installation speed is important
• Cost efficiency is a priority

Choose welded busbar connections when:

• The installation is permanent
• Maximum conductivity is required
• Vibration levels are high
• Space is limited
• Structural rigidity is critical 

In many cases with industrial systems, a combination of both types of connections is used, based on the section of the electrical distribution system.

FAQ’s

Q: Are welded bus bars stronger than bolted?

A: Yes. Since welded joints create a continuous metallic connection, they typically exhibit greater mechanical strength. 

Q: Are welded bus bar joints lower in electrical resistance than bolted?

A: A properly made welded connection usually exhibits lower electrical resistance than a bolted connection. 

Q: Do bolted bus bar connections require maintenance?

A: Yes, regular inspections and checking of fastener torque are necessary to maintain the reliability of the bus bar joint connection.

 Q: Is it possible to bolt copper and aluminum bus bars together?

A: Yes, but bi-metallic connectors or transition connection materials must be used to prevent galvanic corrosion.

 Q: Is it appropriate to use welded bus bars in switchgear panels?

A: They are acceptable if compatible with specific designs  however, bolted connections are preferred for ease of maintenance and future upgrades. 

Q: Which connection type is less costly/coefficient?

A: The cost of owning and maintaining a bolted connection is typically less expensive compared to a welded connection for the life of a system.

 Q: What causes overheating at bus bar joints?

A: The leading contributors of overheating at bus bar joints are loose fasteners, inadequate contact surfaces, corrosion, dirt & contamination, and improper design of joints.

Conclusion

The method you use for connecting busbars can greatly affect how well your system works overall therefore, proper choice will have an impact on efficiency, reliability, and the life of electrical systems. Bolted connections may allow for both flexibility in how they are configured and serviced, as well as make it easy to upgrade their configurations  however, welded connections provide the greatest conductivity and provide the most durable structural integrity over time.

Your application determines what type of connection will provide the best solution. Evaluating these applications before installation helps avoid catastrophic failures and improve performance.

Need Assistance in Finding a Suitable Busbar Solution?

If you are designing switchgear or electrical panels, transformer connections, EV charging equipment, or industrial power distribution systems, working with an experienced busbar manufacturer will simplify the process significantly. Custom busbars that are accurately engineered along with the correct design of the joint connections will maximize performance reliability, enhance safety, and provide longer operating efficiencies.