From Copper to Crimp: What Makes a Premium Electrical Connection?

When specifying and installing electrical connections for datacenters, industrial facilities, renewable energy, automotive, railroad, marine, building automation and other demanding applications, potential failure modes like excessive electrical resistance, wire pullout, and shorting are important considerations.

Using premium crimp connectors can pay dividends by significantly reducing rework and improving reliability. Lower electrical resistance means higher performance. Crimp connectors can provide exceptionally low electrical resistance by using specialized materials, improved structural design, and sophisticated manufacturing processes.

Those connectors deliver superior wire pullout with up to 2.5 times the tensile strength of standard connectors. That results in superior vibration resistance and reliability.

Shorted connections can be a concern without deep barrel designs that prevent wire strands from escaping, and provide robust insulation, including anti-rotational features and deep internal serrations.

This article reviews the comprehensive offering in the Sta-Kon wire terminal product line from ABB and delves into the features that enable these crimp connectors to consistently provide superior electrical resistance, wire pullout strength, and protection from shorts. It closes with a brief review of benefits of getting the Sta-Kon Terminal Kit that includes 12 different Sta-Kon terminals, and the WT112M hand tool.

Ring or fork?

One of the first questions to answer when using wire terminal connectors is: does the application need a ring or fork termination? That depends. Both ring and fork connectors are suited for a variety of applications like marine, electrical panels, data centers, appliances, HVAC, and so on. Forks are better for temporary applications while rings make good permanent connections.

Specification differences between Sta-Kon ring and fork terminals impact their vibration resistance, mechanical security, and suitability for high-reliability situations. The ring terminals deliver maximum reliability and safety while fork terminals optimize speed, serviceability, and efficiency in crowded locations where access is important (Figure 1).

Figure 1: Examples of Sta-Kon ring and fork wire terminals. (Image: ABB)

The design of ring terminals prevents them from inadvertently slipping off and it’s highly resistant to loosening in high-vibration applications. Standard fork terminals can be susceptible to slipping free under the same vibration conditions, especially if not properly installed.

The closed structure of ring terminals also provides a much higher pullout force compared with a standard fork terminal. As a result, ring terminals are more mechanically secure and are often called “permanent” connections providing superior performance for safety-critical power and ground connections and are often mandated in electrical standards.

While ring terminals have better mechanical connection characteristics, fork terminals are faster to install and remove making them preferred in many applications that require fast installation or where frequent service is expected.

All Sta-Kon terminations are tested and listed to UL standards and all applicable products to CSA standards, and they meet applicable military specifications and industrial standards.

Superior design and manufacturing

Sta-Kon terminals, both fork and ring, include important performance features and premium materials, illustrated in Figure 2. The deep internal barrel serrations maximize the surface area and force wire strands into the metal maximizing retention strength and minimizing electrical resistance. The use of 99.9% pure copper and silver solder seams also contributed to low electrical resistance.

During fabrication, the terminals are heated in specific areas using selective annealing. That leaves the barrel soft while the ring or fork tongues are hard to tolerate tightening stress and withstand fatigue.

Selective annealing is an additional process step implemented by ABB when producing its Sta-Kon connectors. It makes the barrel easier to crimp to form a solid connection around the wire without requiring excessive force on the part of the installer. That ensures more consistent installations and improves reliability.

The tongues are “cold formed” to maximize the strength of the copper. That enables it to withstand the strains of repeated bolt tightening without deforming, further improving the electrical and mechanical performance.

Alternative manufacturing processes claim to accomplish those goals by removing material or using a softer copper that has lower conductivity. Those approaches generally increase electrical resistance as well as the odds for shorting and downtime.

Figure 2: Some of the construction details that differentiate Sta-Con wire terminals and enable them to deliver premium performance. (Image source: ABB)

Industry-leading plating processes

A thick bright electro-tin plating that provides better mechanical qualities and superior corrosion resistance is standard on Sta-Kon terminal tongues. Plating alternatives include gold, silver, tin-alloys, and nickel.

Superior production processes, not always followed by other manufacturers, are used for plating. All Sta-Kon terminals are thoroughly deburred and degreased prior to plating to ensure maximum performance and meet the requirements of numerous military and industrial specifications (Table 1).

Table 1: Plating options available for Sta-Con wire terminals. (Table source: ABB)

Best barrels and insulation

It takes care and attention to detail to produce the chamfered (funnel-shaped) barrels of Sta-Kon wire terminations. Chamfered barrels facilitate smooth wire insertion, prevent individual strands from hanging up, and are not available on competitive wire terminals. Once inserted, the longer barrel length compared with competitive designs further increases the crimp performance and better secures the insulation.

Standard barrel lengths found on competitive designs can be up to 50% shorter than Sta-Kon terminals. That increases the frequency of electrical failures and the need to rework connections. Plus, the shorter competitive barrels can result in the insulators coming off during crimping.

Sta-Kon terminals are available to accommodate a variety of wire gauges and stud sizes. The use of extruded insulators eliminates any seam line, reducing splitting when crimped. Barrel insulation choices include:

• Vinyl - Generally the most economical and is rated for use up to +105°C
• Nylon - Offers superior resistance to chemicals and abrasion compared to vinyl and is also rated for up to +105°C
• Heat-shrink insulation - Rated up to +105°C and can offer improved moisture resistance
• Fluoropolymer (Tefzel®) - Rated up to +150°C and offers chemical resistance. Often used in aerospace and nuclear applications
• Non-insulated - Used in confined spaces and temperatures up to +175°C that might melt traditional insulation

High-performance tongue geometries

In addition to the use of a highly refined design, premium materials, and optimized manufacturing process, the performance of Sta-Kon terminals is further enhanced by the availability of a range of tongue geometries. That enables designers to select the best structure for a specific system implementation and operating environment.

The anti-rotation tongues (sometimes called anti-rotation heads) set Sta-Kon ring terminals apart. This feature keeps the terminal secure in the terminal block. That prevents shorting and supports compact installations by allowing installers to place terminals closer together without worry.

Sta-Kon fork terminals are also high-performance designs and are offered in several nuanced geometries classified as standard, locking and flanged:

• Standard forks, like model RB14-8F, are basic open-ended terminals ideal for quick installation on screw terminals.
• Locking forks, like the RA18-6FL, feature angled or tabbed ends to securely grip terminals, preventing the connector from falling off. This design works like a hybrid between a standard fork terminal (for ease of installation) and a ring terminal (for secure connectivity).
• Flanged forks, like the RA18-6FS, have flared (turned-up), angled ends that deliver superior retention and contact area. While locking forks use their tabbed ends to "snap" onto a stud, flanged forks use upwardly bent tips to grab the screw head or mount (Figure 3).

Figure 3: Examples of flanged (left) and locking (right) fork wire terminal designs. (Image source: ABB)

Rapid prototyping, installation, and repairs

The ABB STAKIT Sta-Kon terminal kit is a portable collection of the parts and tools needed to terminate, splice or disconnect wiring for service or installation. It comes in a secure and sturdy latching plastic carrying case and includes insulated ring, standard fork, and locking fork terminals, and other connection components, and can support prototyping, installing, upgrading, and repairing systems. The kit includes (Figure 4):

• Ring terminals (18-14 AWG and 12-10 AWG)
• Standard fork terminals (22-18 AWG)
• Locking fork terminals (18-14 AWG and 12-10 AWG)
• Female disconnects, sometimes called spade terminals (22-18 AWG, 18-14 AWG, and 12-10 AWG, like the 14RB-250F)
• Butt splices (in-Iine connectors) (22-18 AWG, 18-14 AWG, and 12-10 AWG, like the 2RB14)
• WT112M tool for installing #22–#10 AWG insulated terminals
• 100 TY525M Ty-Rap cable ties
• WM-0-THRU9 wire marker book

Figure 4: Sta-Kon terminal kit. (Image source: DigiKey)

Conclusion

ABB Sta-Kon terminals are the premium wire terminal option that improves all aspects of electrical system performance in a wide range of demanding environments including high-vibration industrial, robotics, surface transportation and marine systems, critical installations like data centers and renewable energy, and they are cost-effective for use in building automation, commercial, and light industrial applications.

Sta-Kon terminals are tested and listed to UL standards and all applicable products to CSA standards. They also meet numerous military specifications and industrial standards. They maximize efficiency by minimizing resistance. Their mechanical design and construction reduce rework, improve reliability and simplify installation and maintenance. They feature high-conductivity copper, corrosion-resistant plating, long barrels, funneled entries, selective annealing, and more.

Recommended reading:

1. Subtle Considerations for Connectors in Harsh and Extreme Environments
2. Specifying and Using VFD Cables to Improve Reliability and Safety and Reduce Carbon Emissions
3. How to Ensure Safe and Efficient Modular BESS Deployments Using Pluggable Battery Pole Connectors
4. How to Select Flat-Panel HMIs for Optimal Results in All Industrial Environments
5. Meeting the Challenges of EMI Control and Safety in Compact Industrial Control Panels