Power band
Current bands are used in electrical engineering to conduct large currents under extreme environmental conditions. Due to their construction, current bands are more heat resistant than normal insulated cables or wires.
Basics
Conductors create a flexible electrical contact between two movable conductors. The primary purpose of the contact is to dampen switching surges and vibrations and to compensate for dimensional tolerances and thermal expansion. This type of power transmission can be found in switchgears, industrial furnaces, welding guns for welding robots, transformer and generator stations, electric locomotives, vacuum switches and electrolysis systems . A distinction is made between foil, lamella and stranded tapes as construction variants.
The power is usually conducted via electrolytic copper. With this material, the quotient of electrical conductance and cross section can be maximized very well. Aluminum and cupal sheets are also used as alternative materials to a much lesser extent . The transmission capacities and dimensions of power lines show a wide spectrum.
Construction variants
Foil tapes
Foils with a thickness of 0.04 ... 0.3 mm are usually used for production. In order to achieve the required cross-section, the foils are layered on top of one another and packaged at the ends. The surface is bare, tinned or silver-plated. The film hardness varies between F20 (soft) to F37 (spring-hard) depending on the intended use. Depending on the area of application, the connections are wound, riveted, pressure-welded or produced by a combination of the processes. In the case of current bands with massive connections, the ends are attached by ultrasonic welding, pressure welding, brazing or electron beam welding under protective gas .
Foil tapes are just as electrically resilient as comparable solid copper bars. Compared to stranded tapes, they have the disadvantage of limited mobility in only two directions.
Lamellar belts
Lamellar strips (or lamellar busbars) consist of several copper lamellas, tinned copper lamellas and, more rarely, aluminum lamellas. These are permanently protected by a colored (black, brown, gray, blue or green-yellow) insulation made of polyvinyl chloride (PVC) or silicone . The lamellas lying loosely in the insulation enable problem-free bending and twisting = the tightest angles with the smallest bending radii and twists. At the same time, the strength of the conductor is so high in all cases that it can always be screwed.
Lamella strips can be designed with up to 40% less conductor cross-section than cables with the same current load and, due to their flexibility, offer significantly fewer contact points compared to solid busbars. What applies to the foil tapes also applies here: Lamella tapes have the disadvantage of limited mobility in only two directions.
The slats are 0.5 to 1.0 mm thick and 9 to 120 mm wide. Common cross-sections are available from approx. 20 to 1,400 mm². Example: A slat strip 5x32x1 consists of 5 slats, each 32 mm wide and 1 mm thick, ie it has a cross section of 160 mm².
Stranded tapes
A distinction is made between flat and round strand belts. Accordingly, the highly flexible electrical cord consists of flat rolled fabric strips or braided ropes. For larger cross-sections, several strands are laid on top of or next to one another. The surface can be bare or tinned. The connections are either pipe-pressed and / or pressure-welded. Due to the high compression, the connection ends almost achieve the quality of a solid connection. Another variant is created by applying a commercially available tubular cable lug, either by hexagonal or mandrel crimping.
Stranded strips offer low contact resistance and excellent mobility in all directions. The relatively large surface guarantees good heat dissipation.
literature
- Product information 02/2004 Silicone-coated round strands and high-current connections. Paul Druseidt Elektrotechnische Spezialfabrik GmbH & Co. KG
- Flexible power strips, List 641. Homa Hochstromtechnik.