Q Could you tell us more about your terminal lug manufacturing process
A Established since 1968, LML Products manufactures copper-tube terminals from 10-1000mm^2, along with many other high-current components, at its own facilities in Calne, Wiltshire, UK. All manufacturing is accredited to BS EN 9001.
Parts are only manufactured from optimum-purity original mill-produced copper. In-house recycling is not used owing to the risk of trace contaminants that can seriously impair electrical and mechanical performance.
Whilst custom parts are available in any format, our HD & NT ranges cover most applications. Please contact us for more specific details of terminals required for either protected circuits or applications which may be required to endure high surge-currents.
The standard electroplated coating of tin maintains electrical performance for cables used with normal rated currents and with connection temperatures between -20°C and +60°C. A further range of coatings, including nickel and silver, is available to optimise reliability and performance in critical applications and extreme conditions.
Both standard and bespoke tooling and dies are available for all our terminals along with detailed specifications of process parameters.
All our terminals are capable of compliance with EN 61238, and many other performance standards, but please note that verification requires testing a combination of cable, termination and crimping method. We are more than happy to provide further details on this subject and can also establish many more detailed aspects of electrical and thermal performance through testing, numerical analysis and computer modelling.
Certificates of compliance are also available for parts requiring verification of controlled manufacture or performance
Q What standards to LML terminals comply with?
A Terminals are one component within a mechanical-crimping method of completing an electrical connection.
They are manufactured to multiple designs and modifications for standard and unique (one-off) supply in order to comply with all the various installation requirements that occur.
The critical design features include:
(a) the material used, copper in this case, and its purity
(c) the length and dimensions of its crimping barrel
(d) the design and dimensions of its connection palm
(e) the design and dimensions of the transition from barrel to palm
Generic or universal standards only apply to the copper material and its purity.
In the case of LML terminals we only use mill-sourced copper with no in-house re-cycling. Although some of our competitors do make extensive use of such re-cycling in order to save on costs, this imposes the real risk of introducing contaminants which can seriously affect both the mechanical strength and electrical resistance of the copper.
Particular applications or users may apply their own standards to some of the other design standards or they may only accept a particular set of detailed designs and specifications for a particular set of applications.
It is very important to realise that standards such as (BS) EN 61238 (or the former BS 4579 which it has now replaced) are performance standards that relate to the thermal-cycle performance of a given complete connection or termination under defined repeated cycles of current-carrying duty.
The complete connection or termination comprises:
(1) The Terminal
(2) The Cable
(3) The Type and Method of Crimping or Compression
(4) The Recipient Bus-Bar or Connection
All of these have to be accurately defined, along with the Test Process details, for approval to standards such as EN61238 to be valid.
It is therefore never possible to certify a terminal alone as compliant with EN 61238; performance standards can only be applied to a complete connection.There are several important design features that must be considered when applying terminations to a cable and certainly when selecting a combination of cable and termination for an intended duty cycle. Our own detailed computer-modelling has revealed previously unexpected temperature instabilities that seriously affect the rating requirements of cables and their terminations if high current-density surges are to be expected (e.g. on MV or HV systems). Coatings on terminations, and fine-stranded cables in particular, also need to be carefully considered and specified as materials such as tin readily diffuse into the copper substrate and very seriously damage its resistivity. Testing a connection to EN61238 is enormously costly but, in most cases, either experience in the field with relevant comparison systems and/or iterated design, modelling and testing enable basic design and performance parameters to be confidently specified within sensible cost boundaries.