Power on board – more than just delivering high currents

21st February 2013

Applications with power electronics represent a dynamic market with growth potential. Product developments seek to provide superior solutions to constantly increasing demands within complex environments. The reasons:

  • Customers expect the best possible solutions to meet their application needs.
  • Competitors are forcing their way into traditionally safe territory and increasing the risk of product interchangeability.
  • Technological advancements are broadening the spectrum of solutions. This not only requires greater all-round knowledge but in-depth specialisation at the same time.
  • Updated standards constantly raise the ‘bar’. Increasing levels of safety are demanded. More flexibility when implementing solutions is demanded.

The constraints imposed by the following disciplines must be taken into consideration when designing solutions to meet demands for high installation density or scalability:

  • Electromagnetic compatibility (EMC).
  • Thermal management.
  • Standards & approvals (safety).
  • Ambient conditions.
  • User friendly issues.

And still the puzzle is not complete. The development engineer’s creativity and experience are needed as soon as process-induced factors enter into the equation. As well as production costs, component quality and component availability these factors also include the life-cycle costs (production, logistical and maintenance costs of the component parts).

Various sub-disciplines are closely related to one another, which makes it essential that a holistic view is taken. This is the only means possible to fulfil all of the requirements with regard to functionality, the relevant standards and cost effectiveness. Each stage in the development of a product and each part of a device influences, to a greater or lesser degree, the functional, safety, transmission and value creation chains in their entirety.

As well as electronics components, connection technology is a further area that demands special consideration with regard to design and production. This aspect is often underestimated. The avoidable consequences are: compromises in the design as well as higher costs for production and installation.

All of which is hard to understand. The whole issue looks totally different if we examine the increasing complexity in the field of electronics design, the level of intricacy and the rapid developments in the field of communication technology.

How is it possible that such a simple component can achieve such a level of significance? Well, connection technology exerts a powerful influence over:

  • Plant availability: according to a survey undertaken by the Technical University of Munich some 60 per cent of system failures can be traced back to faults in electrical connections.
  • Device design and dimensions: it is often the connection technology that places limits on the freedom of development and design engineers to progressively miniaturise component assemblies and make the devices themselves more compact.
  • Device approvals: as an interface to periphery components and devices PCB connectors are one of the stumbling blocks in UL or IEC conformity assessment procedures.
  • Acceptance on the part of the end user: general operability issues, handling and overall design.
  • Last, but not least: the costs. These include more than just the costs for hardware (PCB terminals and connectors are presently responsible for some 20 per cent of these costs) or the share of production costs of handling and installation. In the meantime plant operators are casting a particularly critical eye over commissioning and maintenance costs as well.

Meanwhile, market demands require pluggable interfaces to the user. This has the following benefits:

  • Reduced maintenance costs thanks to faster connection times.
  • Wiring mistakes are avoided when replacing a component.
  • Skilled electricians are not required for on-site system assembly.
  • Modularisation and scalability of function, performance and costs with regard to complex systems.

The connection technology should be incorporated at the very beginning of the design-in process.

With its Powermate Range Weidmüller places an innovative range of high-performance connectors at the disposal of the development engineer. This range fulfils all demands with regard to performance and design.

The development engineers of the Powermate Range not only take into account all the relevant standards applicable to plug-in connectors, but also the customary product standards that the development engineer must fulfil for his application to be approved, for example DIN EN 61800 or UL 508C.

The advantage that the development engineer gains from Weidmüller’s integrative and holistic approach is that the components do what the data sheet promises even after the said components have been integrated into the application.

As well as excellent performance, the thoroughly thought-through concept with a wide-variety of innovative characteristics guarantees maximum reliability, greatest possible freedom for implementing solutions and fit-for-purpose design.

The construction and performance classes of frequency inverters are determined to a large degree by the connection technology that is to be utilised. In principal, the different interfaces can be reduced to four basic applications:

This is where Weidmüller’s Powermate Range demonstrates the full extent of its capabilities:

  • Power supply: conductor to PCB with finger-safe field connection.
  • Module assembly: PCP to PCB with finger-safe socket block.
  • Motor feeder or brake: PCB to conductor with finger-safe PCB connection.
  • On-the-fly connection: conductor to conductor with finger-safe socket side.

In future, the Powermate Range will be supplemented by pluggable bus connector. Its current ratio is 57 A bus current to 41 A device current. That means it is eminently suitable for power distribution across device combinations. The bus current offers 40 per cent power reserves for a real and effective power bus.

The system provides solutions for a multitude of applications with four performance classes, two pitch sizes, two connection technologies and three cable exit directions.

Scalable performance

The range performance scale ranges from 500 V/ 41 A through to 1000V/ 76 A. The four performance classes ensure the right performance is available to meet the needs of each application. That means device series with several performance ratings can be equipped throughout with a uniform system. The costs are ‘scaleable’.

In determining the respective current ratings Weidmüller engineers defined the test set-up to match real-life situations as experienced in real-life applications. The rated currents were achieved without using the conductor loops that are sometimes used in the market. The reason: with high-performance power connectors conductor loops act as heat sinks due to their larger cross-sections. Artificially reducing the self-heating factor of the connectors facilitates a higher rated current.

Maximum reliability

In addition to practical rating data, the other product features also guarantee that the product continues to function for decades as intended:

‘Steel for strength and copper for current’ is the principle behind Weidmüller’s clamping yoke connection technology. Together with a low contact resistance even when subjected to temperature fluctuations this achieves totally maintenance-free functionality over its entire lifetime. Responsible for this is the principle of

self-locking. When tightening the screw both clamps generate a durable counter-locking force.

Four-point sprung tulip contacts made of steel ensure a constant high-level contact pressure. Silver-plated surfaces ensure the lowest-possible voltage drop and temperature rise characteristics.

An additional fixing option in the flanges provides strain relief for soldered connections and prevents failures resulting from mechanical stress. That proves to be advantageous when connecting conductors with larger cross-sections.

No matter if when mounting, operating or for maintenance, higher safety requirements are demanded of high-performance power connectors than those of their counterparts used for signals. The components must effectively and reliably rule out incorrect operation when being operated manually. This is a significant requirement, because unskilled workers are quite often detailed to carry out the work due to reasons of costs.

The resolutely safety-orientated design of the range prevents critical operating failures and minimises the risk of injury to personnel and damage to property.

The fail-safe mating face prevents both pole reversal and misalignment when the connectors are being plugged. For example, it is impossible to plug two 2-pole connectors in a 4-pole terminal strip – not even when working overhead. Additional coding channels now allow six coding variations with 2-pole connectors – two are normal. That prevents confusing connectors with the same number of poles.

Inverted versions allow finger-safe functionality at the ‘hot end’. That applies to both on-the-fly and PCB connections.

The innovative multifunction locking mechanism visibly indicates the interlocking status. It guarantees that the connection remains strong in the face of vibration or inadvertent tugging. That is different with screw flanges where it is not possible to see if the screw has been tightened properly. The screw is often not tightened due to sheer laziness, time pressures or unavailability of tools.

Innovative handling

The multifunction locking mechanism also racks up the points for simple and fast handling. Requiring no tools, the clearly visible indexing mechanism can be easily engaged or released manually within a second. It is, so-to-speak, blatantly obvious that this saves costs when dealing with complex systems, during testing and pre-assembly processes as well as commissioning and manufacturing. An additional screw clamp is optionally available but not necessary thanks to locking forces five times above the values demanded by standards.

When designing an application the development engineer has to reconcile many factors and extensive requirements. For example, an EMC-suitable arrangement can be the downfall of a laboriously developed heat dissipation strategy. The clearance and creepage distances required for UL approvals contrast starkly with compact design requirements.

The components are designed in such a manner that, for example, when incorporated in an application and connected in the cutout of a metal housing or laying directly on a heat sink the male connector does not cause any clearance and creepage problems. A component in slice or semimonocoque design could complicate approval to UL 508C even if it is already approved to UL 1059.

A suitable system is available to ensure that the connection technology meets application requirements and not the other way round:

  • Three cable exit directions on the PCB: 90/180/270° to the soldering pins.
  • Three connection technologies: clamping yoke, tension clamp and ring cable lug.
  • Four sizes.
  • Two pitch sizes.

Moreover, four configuration variants for each connection make possible: conductor-conductor, conductor-PCB (finger-safe on the conductor side or on the PCB) and PCB-PCB.

Manufacturing and commissioning often represent a considerable portion of the costs. The Powermate Range demonstrates further benefits when processing and mounting:

  • Optimum anti-rotation feature avoids mistakes when mounting the components: an LCP pin prevents pin headers designed for vertical placement being placed in the reverse direction. The pin is very heat-resistant and also suitable for soldering.
  • Tension clamp connection technology ensures rapid conductor connection.
  • Screw with plus-minus heads for fast, power-driven screw tightening. Searching for a suitable blade is no longer necessary.
  • No tools are required to operate the multifunction locking mechanism.
  • Additional fixing options inthe flanges ensure strain relief for soldered connections.

All components can be adapted to suit special requirements. All options are available beginning with colour variations and printed inscriptions to special contact surfaces and partial assembly through to customer-specific developments. The same also applies to the connection technology for control, signal or bus connections.

Peter Vianden is Product Manager, Portfolio PCB Components, Weidmüller Interface GmbH & Co KG, Detmold, Germany.




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