DESIGNING BESPOKE POWER SOLUTIONS FOR DEMANDING APPLICATIONS

Entrepreneur Henry Ford’s automotive legacy may seem everlasting, but his words on customisation certainly belong in the past. Credited with once saying “you can have any colour you want as long as it is black,” customers nowadays no longer seek a one-size-fits-all solution. The wealth of applications that require power solutions means that product design often comes in a variety of shapes, sizes and power demands. But what must we bear in mind in order to achieve a bespoke product range?


INDUSTRY AND APPLICATION

Whether the resistor is destined for an automotive application or a marine setting, its environment is an important consideration.

In marine and offshore applications, a design could use a range of suitably rated resistor elements such as Incoloy-sheathed mineral insulated elements that are highly resilient to physical damage and safer to use in harsher, corrosive environments. Designing enclosures with a suitable Ingress Protection (IP) rating is also an important factor when supplying to customers in harsh environments.

On board ships, space is often particularly restricted in machine and engine rooms where resistors are usually installed, because they are tightly packed with equipment. In this case, resistor manufacturers may need to design a more compact solution so that the equipment can fit safely on board without taking up a great deal of space and weight allowance.

COMPUTATIONAL FLUID DYNAMICS

Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and algorithms to visualise how gas or liquid flows in certain applications. CFD uses equations that describe how the velocity, pressure, temperature and density of a fluid are interconnected.

Design engineers can use CFD to help them make the most out of their equipment’s unique surroundings, and use them to their advantage. Returning to the offshore example, engineers can assess the wind or wave force that an enclosure used to house electrical equipment is subjected to without needing to physically build it.

Taking things one step further, CFD can also be used to analyse water flow inside water-cooled resistors and better understand the natural air convection of enclosures and to deliver a solution that is bespoke to these unique elements.

THEM’S THE BREAKS

Dynamic braking resistors (DBRs) are an essential component in elevator operations. Without them, the lift wouldn’t slow down in the time determined by the drive. It is therefore critical that the system works every time, without fail.

An elevator in a local supermarket wouldn’t be tasked with the same load as one carrying passengers to the top floor of The Shard. Therefore, custom resistors must exactly match the elevator manufacturer’s design specifications.

Before providing the right resistor, Cressall first evaluates the energy per stop, the duty cycle and the ohmic value. The first two are typically considered as a single variable — the required power of the resistor. The energy per stop is the sum of the kinetic, rotational and potential energies, minus any frictional losses and any electrical losses in the motor or inverter system.

Because all the energy produced by the braking process is used in heating the resistor, the characteristics of the duty cycle are critical before specifying the right size for the DBR in order to reduce heating. With these calculations, we can be sure that we are providing a DBR that is bespoke to the individual elevator, helping to deliver unprecedented security where safety is a top priority.

Customisation extends far beyond having the latest car in a stand-out colour. For some industries, their unique demands mean that an off-the-shelf model simply won’t suffice. In these cases, building a relationship with a resistor manufacturer that has over 100 years’ experience in designing and manufacturing resistors can help make sure the size, shape and power demands of the finished product are as unusual as required.

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PRODUCT RECALL ON AC30 PORTABLE LOAD UNITS

ac30 portable load bank

In 2019 our Quality and Engineering teams became aware of a potential issue with some AC30 Portable Load Units.

Fortunately, our records were able to identify all customers who had purchased units deemedat risk and a systematic process of recall, rectification and return to Customer was initiated.  This will be completed by the end of 2019.

For further information please contact quality@cressall.com

NEW SURGE SUPPRESSORS FOR EXTRA PROTECTION

Zorc surge suppressor rangesurge suppressor

ZORC™ produce a range of unique high-frequency transient overvoltage surge suppressors for the protection of motors, transformers, generators and filter banks from steep wave-front, short rise-time, high magnitude, spikes, surges and other transient voltages, generated by switching and certain other sources.

The protective characteristics of ZORC™ provide comprehensive insulation coordination with both the CiGRé and IEEE motor impulse voltage withstand characteristics at all practical surge magnitudes and rise times.

Overvoltages are not only related to atmospheric impulses, in reality faults and damage can often be caused by other overvoltages such as switching overvoltage, transient recovery voltages and iron-resonance overvoltages. Good reasons to consider the installation of the ZORC™ surge suppressor.

Key Features:

  • Saves money by eliminating production downtime due to insulation failure.
  • Protects motors, generators and transformers throughout their service life.
  • Eliminates multiple pre and re-strike transients associated when switching on or off with vacuum and other switchgear types.
  • Standard and intrinsically safe models available.
  • Three and single phase

Product Functions:

  • System Voltage: 3 phase 400V to 13.8kV with single phase at 15kV
  • Transient protection: 0.1 to 0.2 micro seconds range
  • Special compact versions that can be fitted within most motor/transformer terminal enclosures or switchgear panels
  • RC single phase units available from 24-40KV

Applications for motors include:

  • Fans
  • Compressors
  • Conveyors
  • Generators
  • Crushers
  • Motor-generator sets
  • Pumps
  • Mills
  • Mine winders
  • Mini and mobile substations
  • Power station auxiliaries

Other Applications include:

  • Induction and arc furnaces
  • Mini and mobile substations
  • Dry type transformers
  • Refrigeration machines

To find out more about these new surge suppressors and how they can help you secure your electrical installations from damaging overvoltages, download our new data sheet  or contact Cressall today.

POWER RESISTOR ENCLOSURES:
SEEKING THE ANSWERS

Cressall, has released an informative infographic explaining the essential questions to ask when designing an enclosure.

The guide aims to support design engineers as well as resistor end users across all industries to understand the requirements of their power resistor enclosure.

The infographic is now available to download here.

Power resistor enclosures provide a number of functions, including protection from harsh weather conditions, cooling and preserving the safety of the public. Each of these specifications will vary, dependant on the exact requirements of the client, and the resistor they purchase, however a full understanding is crucial to the design phase.

The research stage is usually undertaken when thecustomer provides an initial specification, but on some occasions, this does not happen, therefore it is the manufacturers responsibility to ask those important questions.

The infographic explains five questions that must be answered in order to design and manufacture an effective enclosure that meets all the required specifications. These queries cover the final resistor environment, industry challenges, aesthetic considerations, health and safety and choices around shipping and installation. By thinking about these points early, the final product can be designed to meet each and every requirement.

“We produced this infographic to provide design engineers, as well as the end user, a checklist of things to consider when they are planning their resistor and corresponding enclosure,” said Andrew Keith, engineering director at Cressall Resistors.

“Sometimes enclosures can be left as an afterthought, but this will rarely achieve the most efficient, advantageous solution. Thinking about the enclosure at the same time as designing the resistor is crucial to ensuring the final product will meet all the requirements, reducing the risk of compromises having to be made.”

Cressall works with clients worldwide to design and manufacture a range of resistors alongside enclosures, including dynamic braking resistors (DBRs), neutral earthing resistors (NERs) and harmonic filters. The full range includes specialised resistors for a number of sectors including rail traction, renewables, marine and offshore.

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