POWERING AUTONOMONY

ENERGY-EFFICIENT BRAKING CRUCIAL TO SUCCESS OF AUTONOMOUS VEHICLES

When a self-driving Uber crash led to a fatality in 2018, to many, it seemed that the autonomous vehicle revolution was over before it had chance to gather speed. If autonomous vehicles are to make it onto our driveways, braking systems will be crucial to minimising accidents.


One year after the Uber crash, the National Transportation Safety Board (NTSB), an independent US government investigative agency, concluded that a major factor in the collision was a misjudgement by the vehicle’s safety operator — or, the human that sits in the vehicle and monitors the autonomous driving system.

While it seems that human error will never go away, manufacturers have not given up on the concept that the right technologies can help autonomous vehicles steer away from disaster. Automotive giants, like Jaguar Land Rover (JLR), continue to invest in autonomous technology. JLR’s Project Vector concept aims to have an “autonomy-ready” and “multi-use electric vehicle” on the road by 2021. 

While it’s clear that the future will be self-driving, how will manufacturers avoid the accidents of the past — and what role can advanced braking systems play?

FOLLOW THE ROUTE

Operating from March 2018 to June 2019, the Route 12 driverless bus concept successfully provided Schaffhausen, Switzerland with a driverless bus system over a year. Big cities can learn a lot from the small Swiss town and, last year in Germany, Berlin’s public transport company, Berliner Verkehrsbetriebe (BVG), also tested out its own autonomous buses.

Autonomous transport offers many benefits to towns and cities alike, not least in terms of safety. The UK’s Department for Transport reports that 27,820 people were killed or seriously injured in reported road traffic accidents in the year ending June 2019. Leading causes for these accidents included speeding, lack of focus or driving under the influence — all of which are results of human error. 

Programmable driving systems should eliminate these unsafe human habits, of course. In addition, driverless vehicles can also reduce traffic congestion by following fixed routes that are simpler to handle than the various and complicated routes along which a taxi or car usually travels. 

REGENERATIVE BRAKING

Choosing the most effective system for an autonomous vehicle goes beyond merely bringing the vehicle to a stop. As most autonomous vehicles in the future are expected to be electric vehicles (EVs), braking systems will also play a crucial role in optimising energy consumption.

This applies to EVs used for public transport, where multiple stops and starts along a single route are an energy drain. When these stops occur, and because the electric motor behaves like a generator under these conditions, the EV releases energy that is fed back into the drive system. This energy needs somewhere to go, so heads towards the EV’s battery as part of a process is known as regenerative braking. 

If the battery is full, and the EV has no other means to dissipate the excess energy, then the speed of the vehicle might be limited in order that the mechanical brakes can safely bring the vehicle to a stop without the possibility of causing brake fade or failure. 

To remedy this, a braking resistor, such as Cressall’s EV2, can dissipate excess energy when the battery does not accept the charge. This type of braking is known as dynamic braking. Wherever possible, braking should be regenerative rather than mechanical. This creates the possibility of storing and re-using braking energy, rather than just dissipating it as waste heat. 

Furthermore, many public service and heavy goods vehicles are fitted with auxiliary or endurance braking systems that work in tandem with the service brakes. The EV2 is an ideal substitute to these mechanical, hydraulic or magnetic systems. 

Heating also plays an important role in making use of this regenerated energy. The EV2 is a liquid cooled resistor. Specifically, it is cooled by pumping the cold liquid that comes into one end of the system, which then absorbs the heat generated by the resistor. This heated liquid can be pumped through a radiator, then used to provide heat to the cabin of the vehicle for a more comfortable passenger experience. 

This method of heating reduces the amount of energy required from the battery, and uses heat that would otherwise have been wasted.  

While the wide-spread adoption of autonomous transport has yet to become a reality, it’s not difficult to imagine the day when cars will brake on their own, as commanded by autopilot. After all, electric steering systems already perform a similar function. Braking technology can’t change the mistakes of the past, but it can be a huge driver in delivering energy-efficient autonomous transport. 

To find out more about Cressall’s EV2 for electric vehicles, click here

CRE413

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.

CRE389

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.