According to a survey by a Canadian energy supplier, almost 40% of power failures can be traced to loose contact parts. Today, locking elements connected by mechanical screws are often used, and they are only partially or not suitable for the specific requirements of electrical screw connections.
Recently, a production facility was shut down due to loose electrical screw connections. This initially causes an increase in contact resistance and then a voltage loss. Teckentrup was unable to find a suitable screw locking component to solve this problem, so it developed NSK-E-a lock washer that meets the specific requirements of electrical connections and related standards.
In fact, loose screw connections can cause increased contact resistance, voltage drop/fluctuation (flickering), and heat generation at the contact point until the contact point itself or surrounding equipment burns. Loose contact connections can cause serious damage, which requires a new method.
Characteristics and requirements of screw connections in electrical applications
The main task of electrical connection is to transmit power. The quality factor ku plays a decisive role in evaluating the quality of the joint/screw connection. This represents the ratio between the resistance in the joint and the resistance in the busbar. Therefore, the purpose of the joint is to ensure that the quality factor remains as constant as possible during its service life. It is necessary to maintain the contact pressure required by the soft conductor material throughout the life of the joint to maintain the quality factor and thus keep the resistance constant.
In order to obtain a stable contact pressure, the screw connection must fulfill two functions:
Elastic function: The elastic function is necessary because different coefficients of thermal expansion and drastically fluctuating operating temperatures will cause changes in the mechanical tension in the threaded connection. The settlement process must also be compensated. Settlement is where the surface of the connecting element becomes flat. In this regard, the number of joints and the soft conductor material mixture are important. Due to the short clamping length, the required elasticity of the threaded connection can only be achieved by flexible locking elements.
The function of the screw locking element: When the screw is loosened due to vibration and lateral displacement, this may also cause the contact pressure of the electrical screw connection to decrease, resulting in the type of damage already described. Due to the use of different materials-steel, copper or aluminum, thermal expansion with different coefficients of expansion may cause screw connection failure; settlement in the joint; and vibration-such as at high frequencies or due to the movement of the entire system.
Inappropriate spring and screw locking elements
In the 1990s, the locking effect of the springs and screws of the components used at the time was checked. As a result, the standards for spring rings, serrated washers and toothed washers have been withdrawn, which means that they no longer represent the most advanced technology. The use of two screw locking elements, such as spring rings and washers, also fails to meet the requirements.
teckentrup set this challenge for himself and developed NSK-E lock washers specifically for the electrical industry. With the company's many years of experience in mechanical screw locking components, teckentrup is able to respond to specific requirements and develop the best solution through appropriate testing methods. Through cooperation with end users and external testing laboratories, NSK-E has also successfully tested under extreme conditions.
The test procedures it accepts include DIN 25201-4 (Appendix B), DIN 267-26 and IEC 61373. NSK-E has demonstrated excellent performance in all quality inspections, which means that the washer can be used as a locking element that complies with the most common standards such as DIN 25201-3, DIN 46200, DIN 43673-1, and DIN EN 50343.
There are two variations of washers, including coated spring steel and stainless steel 1.4401. Washers are currently available in sizes M3-M16 and can be combined with traditional screws. Due to its arched shape, NSK-E has a particularly significant spring effect, which means that the contact pressure and the connection resistance of the joint can remain almost constant for a long period of time.
The reinforced teeth on the top ensure a positive locking fit with the bolt head/nut. This ensures that the components will not loosen when subjected to cross loads. In order to prevent damage to the flexible connection components, the bottom surface of NSK-E has a profile similar to a slide rail. When installed in a tightened threaded joint, the washer is located on the counter support, so despite the shorter installation dimensions, the risk of exceeding the surface pressure is reduced.
In NSK-E, users can freely use an integrated screw locking element made of spring steel or stainless steel, which is specially developed to meet the requirements of electrical screw connections.
Claire joined the magazine in 2012 and developed her industry knowledge through numerous company visits, exhibitions and conferences she participated in in the UK and abroad.
Claire is proud to keep readers up to date with the latest industry news.
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