Live electrical conductors and their contact points have additional requirements with regard to heating, material pairing and surface properties.. More
In low-voltage technology, electricity is carried through a large number of specific components such as cables, rails, power distribution components and the corresponding connections and terminals. But even within devices, the power must be routed via internal busbars or cabling and connected to other parts. Every current-carrying electrical conductor has an electrical resistance, which leads to heating. This must be observed in accordance with the further mechanical and electrical requirements and the conditions of use and may place additional requirements on the current-carrying part or surrounding materials.
In addition, every connection of two current-carrying electrical conductors is a contact point with an additional contact resistance. A distinction is made between permanent contacts that cannot be detached, such as crimp, solder and weld connections, and detachable contacts, such as plug, clamp and screw connections. Environmental conditions and the material pairing can lead to corrosion, which can lead to an interruption in the power supply or to melting. This must be taken into account when designing and dimensioning the material pairing; a surface treatment (tin-plating, silver-plating, gold-plating) may be necessary.
Electrical contacts must reliably interrupt a circuit or establish an electrical connection. With this switching, an arc occurs at higher currents and voltages. More
The occurrence of an electric arc during a switching process requires a minimum current intensity and a minimum voltage. Current strength and voltage depend on the contact material. In the case of high service life requirements, for example in relays, one tries specifically to avoid an electric arc. However, an arc also enables dirt on the contact surfaces to be broken up. If there is no arc, other technical solutions such as friction and rolling contacts or hermetically sealed chambers must be used in order to avoid contact problems and achieve a high level of contact reliability.
In higher current and voltage ranges, the breaking arc is used specifically as an aid for the switching process and fulfills an important technical function. The mechanisms, switching chamber, contacts and materials must be designed and optimized in accordance with the areas of application and the breaking capacity to be achieved. At high rated outputs, this leads to complex extinguishing chamber geometries with perforated plates, blow magnets, hard gas elements and flow-optimized discharge geometries. In addition, the arc leads to considerable contact erosion and thus wear to the contacts.
In return, the pre-ignition arc with its risk of contact welding and material migration must be controlled when switching on.
In addition to contact-based switching, semiconductor components such as thyristors also enable contactless switching. In the case of so-called hybrid switches, a contact is first switched off contactlessly and then a switching contact is opened without current to ensure an isolating distance.
The insulation coordination according to DIN EN 60664 (VDE 0110) describes a method for dimensioning insulating clearances and creepage distances for electrical equipment in low-voltage systems. More
The insulation coordination is necessary for all electrical devices, products and equipment. On the one hand to ensure the correct functioning, on the other hand to guarantee the safety of the user or application. The technical requirements are defined by the conditions of use (degree of pollution and overvoltage category). Compliance with creepage and clearance distances must be taken into account early on in a design, as this has a significant influence on the technical implementation of solution principles.
In low-voltage technology, on the one hand, purely mechanical, temperature, voltage, or current releases are used to monitor operational parameters; on the other hand, there is the area of remote release. Electronic solutions are increasingly used in the field of measurement and automation technology. More
The triggers are often simple mechanical meanisms based on thermal bimetals, solenoids, piezo actuators or shape memory elements. In addition, there are springs as energy stores and levers and translations for coordinating forces and paths. The construction of such mechanisms requires a high technical understanding of the basic physical principles - but often just a lot of attempts and tests to adjust and optimize the respective application limits.
Each economic area has its own standards and rules for products or electrical equipment so that they can be placed on the market. This often leads to complex requirements for the products and components. More
The Low Voltage Directive (Directive 2014/35 / EU) defines a legal framework for standards to be met for all electrical equipment for use at a nominal voltage of up to 1000 V for alternating current 1500 V for direct current in the European Economic Area. A large number of product standards such as DIN EN 60947 (VDE 0660) with its 20 parts, or DIN EN 61439 (VDE 0660-600) for switchgear combinations, or DIN EN 60999 (VDE 0609) for connecting material. In group 6 of installation material and switchgear, the VDE lists more than 3,000 valid standards. Even in group 4 with, for example, DIN EN 61810 (VDE 0435-201) there are well over 500 valid standards.
Often products are developed not just for one economic area, but for several. Accordingly, there are other regulations such as UL508 for the American market. In the automotive industry, many requirements are defined by factory standards and delivery conditions. Often the critical requirements are in the details of the respective test specifications. Compliance with these important and critical requirements as early as possible in the development process is crucial for product development. Furthermore, extensive knowledge of the use of switching devices, relays, counters or charging technology and their special conditions of use is also required.
Plastic parts have special requirements on the design and construction of the individual parts and components. More
A plastic-compatible design and construction requires both consideration of the material properties and the requirements that result from the structure of the tools and the manufacturing process of the plastic parts. Widespread is the use of injection molding processes with its requirements for the shape direction, wall thicknesses and draft angles in order to enable simple, reliable tools and dimensionally stable parts in series production. The number of items and the expected service life determine the possible solutions and the necessary specifications.
Mechanisms and gears
Electrical equipment has various mechanisms for operating or switching. More
Mechanisms and gears are used to transmit force or torque or are intended to provide a suitable translation between distance and force. Often the installation space is limited or a high level of performance should be achieved with as few simple, easy-to-assemble individual parts as possible. Furthermore, special attention is necessary for the dynamic behavior.
Coils as sensors and solenoids
Coils can generate or detect a magnetic field and are therefore used as sensors or actuators. Solenoids are often used as switch actuators in relays or contactors. But they are also used where things have to be moved. Coils are also used as sensors for measuring current. More
The calculation and design of coils with and without iron core for direct voltage or alternating voltage is an essential basis for the design of sensors or solenoids based on them. The ampere-turn for the magnetic flow is an outdated, but clearly descriptive unit of measurement.
Electrical equipment and components are always subject to self-heating. In addition, the devices and components must function reliably in a wide variety of ambient temperatures and conditions. More
In normal operation - but especially in the event of a fault, for example in the event of a short circuit - strong heating occurs. In particular, these must not affect the function of the structural components or the insulating components. A precise knowledge of the occurring loads is just as necessary as well-founded material knowledge. In contrast to metals, the material properties of plastics, such as the modulus of elasticity, can change significantly and suddenly above certain temperature limits.
The heating behavior is also important in connection with fused devices and components. Since classic fuses can only be used within narrow temperature limits.
EKL has extensive special literature on low-voltage technology, automotive high-voltage technology and related topics.
EKL has an extensive sample collection of switchgear and components on the market, but also of historical devices and technical solutions.
Prototyping & Test Equipment
Our in-house prototype construction has a high level of skill in the construction of principle samples, the assembly of test items and the construction of test devices.
Thanks to our test laboratory, we have extensive in-house expertise in test regulations and execution.