Power connections
Flexible, Rigid, and Laminated Busbars: How to Compare Them
Flexible foil, braid, rigid bar, and an insulated laminated assembly solve different mechanical and electrical problems. The names overlap.
On this page
Some flexible busbars are stacks of copper foil. Some products called laminated busbars are flat conductors bonded with insulation so the electrical design can use that geometry. The words show up on both kinds of parts. Compare the build and the job, then match a supplier that publishes that build.
The terminology overlaps
nVent describes ERIFLEX Flexibar as multiple layers of thin electrolytic copper with an insulating sleeve, and the Advanced tinned-copper page calls those layers a stack of thin tinned copper. EMS describes expansion busbars as flexible busbars made of thin packaged laminates of copper or aluminum with solid connectors. Mersen describes a laminated bus bar as layers of fabricated copper separated by thin dielectric materials and laminated into one structure. Storm uses laminated bus bar for multi-conductor parts it associates with lower stray inductance, and it lists flexible braided connectors as a separate product.
A laminated flexible conductor and an insulated laminated assembly can both be called laminated. They are not interchangeable because both words appeared on a catalog line. The manufacturer guide is the wider U.S. shop list. This page stays with construction.
How the main constructions differ
Rigid fabricated bars
A rigid bar is a copper or aluminum conductor that holds its shape. Shops such as Keats, Monti, and Approved Sheet Metal describe cutting, stamping, or forming that kind of part. The bar can be drilled, bent, and plated. It does not provide the movement a foil stack or a braid is built to allow. Where the equipment moves, expands, or vibrates, a rigid joint may need a flexible link at the connection instead of a longer rigid bar.
Flexible laminated conductors
EMS builds the flexible section from thin lamellae, 0.2 mm copper fins for its Cu-HCP expansion busbars and 0.3 mm aluminum lamellae for the aluminum version, with solid connectors. The page says these parts compensate for thermal expansion and for vibration, and that they are manufactured according to DIN 46276 part 1, with current-carrying capacity designed according to DIN 43670 at an air temperature of 35 °C and a rail temperature of 65 °C. That design basis is EMS's statement. It is not a rating you can copy onto another maker's foil.
nVent's Flexibar page describes a sleeved stack that can be bent, folded, or twisted, with connections made by punching and bolting through the laminates, by clamping the end, or by welding. The family page states a range from 27 mm² and 125 A up to 1200 mm² and 2,800 A. The Advanced page repeats a wide current span and warns that its temperature-rise table does not include heat dissipated by the switchgear. Use the product's own table for that product. Do not treat the span as a score against a rigid bar.
Braided connections
Storm manufactures custom flexible braided connectors and says the build can follow a specified length, hole pattern, or ampacity requirement. The page does not publish a catalog of braid constructions or a movement envelope. A braid is a woven link. It is not a rigid bar with a loop bent into it, and it is not Mersen's dielectric-separated laminate. If you want braid, the request has to say braid, termination, and how far the joint moves.
Insulated laminated assemblies
Mersen's definition puts dielectric between fabricated copper layers and then laminates them. The page lists insulation materials that include Nomex, Mylar, Kapton, epoxy glass, and others, and finishes that include tin, tin-lead, nickel, copper, silver, and gold. It describes the reason for the build in electrical terms: lower inductance, higher capacitance, and a controlled geometry, and it says sizes run from very small surface-mount parts to multilayer bars longer than 20 feet. Storm's laminated bus bar copy is in the same family of claims: multi-conductor parts associated with reduced stray inductance. An insulated laminate can include a hinge or a formed shape, as in one Mersen industrial example, and still be a designed assembly rather than a free foil stack.
Which requirements change the choice?
Movement and vibration point toward a foil stack, an expansion busbar, or a braid, because those products are described as allowing movement. A fixed joint inside a panel can be a rigid bar. A power-electronics layout that needs conductors paired with insulation is the problem Mersen and Storm describe for laminated assemblies. Thermal expansion is the reason EMS gives for expansion busbars. Routing and the available bend space show up in nVent's claim that Flexibar can take a small bend radius. None of these pages publish a test that ranks the four builds against each other.
| Question | Rigid bar | Flexible foil or expansion link | Braid | Insulated laminate |
|---|---|---|---|---|
| What the pages emphasize | Shape, holes, plating, and a conductor that stays put. | Thin layers and movement between solid or clamped ends. | A woven connector made to a length and hole pattern. | Copper layers separated by dielectric for the electrical layout. |
| Movement | Not the purpose of the bar. | Described for expansion, vibration, or bending in place. | Described as a flexible connector. The envelope is not published on Storm's page. | The assembly is a structure. A special joint may be designed in. |
| Insulation | Added by sleeve, coating, or standoff when specified. | nVent uses a sleeve. EMS describes packaged laminates and does not use that sleeve description. | Not described as an insulated power laminate. | Dielectric is part of the build. |
| What the RFQ has to add | Drawing, material, finish, quantity. | Movement, terminations, and the maker's current basis if you are using their table. | Length, ends, and movement. | Conductor count, insulation, and the electrical requirements the designer already set. |
Suppliers and the constructions they publish
These families are not substitutes. Storm, in Decatur, Tennessee, publishes custom rigid bars, laminated bus bars, and braided connectors. nVent publishes Flexibar as a sleeved flexible busbar and does not name the factory city on the product page reviewed here. Mersen publishes custom laminated bus bars and describes a global manufacturing footprint without naming one U.S. plant on that page. EMS Elektro Metall Schwanenmühle lists its expansion-busbar work at Schwanenmühle, 66851 Horbach, Germany, and states ISO 9001:2015. More U.S. rigid-bar shops are on the manufacturer guide.
What to include in the RFQ
Name the construction in the first line. Add the movement envelope if the joint has to travel. Add terminations, insulation, environment, and any electrical requirement the design has already validated. Do not ask the supplier to invent the ampacity from a sketch. The request builder on the custom busbar page holds those fields. Finish still needs its own line, covered in the tinned copper guide.
Common selection questions
Is a laminated busbar flexible?
It can be, when the laminate is a stack of thin foils, as on the EMS and nVent pages. Mersen's laminated bus bar is defined by copper separated by dielectric. That definition does not say the part is a flexible link. Read the product, not the adjective.
Can braid replace a rigid connection?
Only when the joint is supposed to move or when the designer has accepted a braid for that connection. Storm treats braid as its own product, with length and hole pattern among the inputs. A braid does not carry the same geometry as a rigid bar, and the pages reviewed here do not give a substitution rule.
What does a supplier need to assess a substitution?
The current drawing, the proposed construction, the movement, the terminations, the environment, and the electrical requirements that already govern the joint. A supplier can say whether it builds that construction. The design owner decides whether the substitution is acceptable.
Sources
Construction claims are limited to the product pages linked below. A Rittal flexible-busbar paper was in the starting list and is not cited, because this pass did not use it as a source. No inductance or vibration number was added beyond what a named page states about its own product.