Electricity is, in the truest sense of the word, the lifeblood of our modern society and economy. Because without it, nothing works. Circuit-breakers are of crucial importance for the safe operation of our power grid. For example, it is their job to switch the entire output of a power plant (in the gigawatt range) on and off and to control voltages of up to 1,500 kV. The cold-rolled ball screw drive type Carry from Burg (CH) plays an extremely important and responsible key role in this.
High voltage, fewer losses
Electrical energy is transported from the electricity generator, for example from the power plant, to the electricity user. In order to save losses and therefore costs during electricity transmission, the aim is to achieve the lowest possible current levels. High voltages are used in order to still be able to transmit a lot of power. High and extra-high voltages of up to 1150 kV are used here. The entire European electricity grid has a length of around 1.8 million kilometers.
The challenge of a circuit breaker
Regardless of its position in the network, a circuit breaker has two tasks: The daily switching of lines during normal operation and the interruption of the power supply in the event of an overload or short circuit. A circuit breaker is a mechanical switching device and must be able to "tame" power of several GVA within fractions of a second. Interrupting the flow of current leads to a voltage flashover between the two circuit breakers, at least briefly. Contacts and a self-sustaining, self-sustaining Gas dischargewhich is called an electric arc. Electric arcs have enormous energy. At temperatures of over 50,000 °C and a volume of less than one liter, pressures of up to 100 MPa can occur. The ionized gas (Plasma) not only continues to manage Electricitybut reduces the service life of the component. With high currents, it can even destroy the switch. Circuit-breakers are designed in such a way that the arc that occurs when the switching contacts open is extinguished quickly and without damaging the switch, thus interrupting the current flow.
One step ahead with the right technology partner
A leading global technology company was looking for an absolutely reliable drive solution to separate the heavy metal contacts in the circuit-breakers at lightning speed. The energy technology group found what it was looking for at Eichenberger Gewinde AG. For decades, the Swiss thread specialist has been supplying spindle solutions that not only excel in terms of performance, quality and reliability, but also support the decisive innovative edge. When it comes to the design of specifically integrated drive components, customers worldwide benefit from Eichenberger's in-depth knowledge and amazing development and manufacturing potential.
The thread roller always focuses on a needs-oriented, constructive exchange with its partners. On the one hand, the art lies in developing exceptional customer solutions and, on the other, in ensuring efficient and advanced production processes. Forward-looking, vital thinking is firmly anchored in Eichenberger's corporate culture. The ideal "in-house" company structure means that development, production, quality assurance and agile prototyping, including thread rolling tools and end machining, can be offered simultaneously. This allows for remarkable flexibility and adaptability. The employees' deep awareness of quality is coupled with a correspondingly modern machine park. Thanks to these factors, a great deal can be achieved, particularly in Switzerland. The permanent development of practical customer solutions is Eichenberger's passion. Thread forms that are outside the norm are the sought-after tasks.
Plus point thread rolls
Recognizing the potential in this drive, the energy technology manufacturer opted for the robust cold-rolled ball screws from Burg (CH), which are produced in large series using the cost-effective thread rolling process. In contrast to grinding, milling or turning, thread rolling does not cut the longitudinal fibers of the material, but deflects them. The result is a compressed, smoothly rolled, extremely resilient surface, which is essential for a long service life of the spindle. The roughness values of around Rz 1.0 on the thread flanks and in the base radius as well as a significantly reduced notch sensitivity also provide a major advantage. The rolling friction coefficient for steel balls is 0.003 to 0.001 compared to sliding friction steel on steel (lubricated) 0.1 to 0.05. The excellent sliding properties of the cold-rolled ball screw ensure minimal abrasion and offer little surface area for contamination. This makes low-noise rolling of the balls child's play.
Absolute reliability
"Rarely challenged - but then in no time at all"
A high-voltage short circuit has already reached its maximum value after 5 milliseconds. Fortunately, interruption of the power supply in the event of a short circuit is rarely required. However, if this occurs unexpectedly, the absolute reliability of the mechanical drive elements is essential! The Carry ball screw drive guarantees maximum functional reliability with enormous performance (efficiency > 0.9) and robustness. Carry prepares the mechanical closing and opening process of the circuit-breaker with the aid of coil springs. Two solid push rods are firmly connected on both sides to the custom-made nut, also known as the carrier. These two levers set the huge, spring-loaded striking armatures in motion, which separate the metal contact extremely quickly. Despite the most adverse weather conditions and large temperature differences, the cold-rolled, heavy-duty carry performs its task with absolute reliability and maintenance-free operation.
The customer-specific requirements for the ball screw drive with integrated customer interface in the nut were "substantial and varied". The highest demands were mentioned with regard to axial force and geometry. Tribological aspects such as friction, wear and lubrication were listed as important requirements that had to be met. The tricky task of adapting the exterior of the nut body to the special interface requirements and the kinematic conditions proved to be particularly challenging. Due to all the requirements, various dimensions of the Carry ball screw, consisting of the cold-rolled threaded spindle and the specific drive nut, were developed for worldwide use.
When reliability and customer benefits are no coincidence
The flexibility of mechanical-dynamic functional elements contributes significantly to the success of drive technology projects. The decisive factor here is the realization that quality and reliability must be "developed into" a product. The high-tech testing systems from Eichenberger Gewinde AG are therefore indispensable in many phases of product development. Only when spindles, nuts, balls and lubrication interact perfectly can the highest demands be met. Due to the tight tolerances for torque, axial play and concentricity, a 100 % check is carried out on a special test bench. It is not only in the automation, automotive or medical industries that the strictest requirements for complete traceability, for example, are a decree. On request, Eichenberger can easily apply data references to the ball screw or lead screw by means of permanent laser marking as a data matrix code. Today, it is all about a technological edge and higher power density, with a tendency towards reduced investment costs. If the inventor of the product is also its most competent manufacturer, the advantages are obvious.
Service provider in development
The need to solve practical tasks is perpetual. Eichenberger Gewinde AG is successfully exploiting the opportunities this presents and has succeeded in establishing itself in the drive technology niche with its customized rolled screw drives. The Swiss thread specialist has clear goals: The rolling (cold forming) of threads and the production of lead screws (spindle and nut). Using state-of-the-art production methods and developing new dimensions, Eichenberger supports its customers in "their" innovation.
The challenge for the designer in Switzerland, a high-price country, is this,
very high technical value in a market-driven, competitive product
to develop. It is not only technological knowledge, research and development that is needed, but the additional mastery of efficient manufacturing processes provides a competitive advantage. If the inventor of the product is also its most economical manufacturer, something can really be achieved, especially in Switzerland.
