Latest PCB technology boosts power electronics performance

Technology trends - such as energy efficiency, increasing power density or the overall integration of power, signals and data on the same system platform - are both, a challenge for engineering, but also a chance on diversification and innovation. Thus, trends drive growth and attempt to be a decisive factor for an application's success.

Obviously, one of these trends is the increasing performance of power electronics, in correlation with the rapidly growing demand for applications based on power electronics, such as frequency converters, servo drives or photovoltaic devices.

From this point of view, it is recommended to consistently align the component specifications with each phase in the application's life cycle - including conception, design, construction, production, installation and maintenance. This guarantees the optimal level of integration into the system environment. The function and form of the application's connection method plays a key role that should not be underestimated, as it influences several critical technical and economic factors, such as:

- Electrical, thermal and mechanical design flexibility.

- Costs of production, installation and maintenance.

- The user satisfaction level as influenced by the ease of use.

- The facility availability as a link on the transmission path.

- The long-term reliability, especially under threshold limits, and last but not least,

- The safety provided to man and machine.

Referring to power applications, definitely two of the challenges that electronics engineers have to solve, is first the question of thermal management, and second the design of the current carrying systems. Mixed up with EMC requirements, plus the continuous demand for smaller devices, plus production efficiency and last but not least, the cost reduction, you gain an exciting play on balancing technical and economical issues.

One does not need to mention that each of the topics is a science on its own. Looking at the conducting elements of a power electronics device, we may mainly identify the wires, the PCB, usually some bus bars and the junction points.

For example, due to an ongoing improvement of the manufacturing process, particulary the performance of the PCB has been increased along the recent years. Moving from 35µm to 400µm thick-copper paths, extended by iceberg technology and supplemented by wire laid technology, a state-of-the-art board with copper bar inlays is able to carry currents of 800Amps and even more (Fig. 1).

It is one question to get copper bars with a size of 3 x 15mm integrated to a PCB, and another one to get such a power board connected to the peripherals. It is also one thing to stick on the 'good old' bus-bar for the distribution of high currents, and another thing to minimise the dimensions of the device - while maintaining the same level of performance and protection against electrical shock. Finally, it will be one solution, to connect ring lugs to stud bolts, and the other problem to replace a device immediately because every minute of downtime burns loads of money due to production stop.

The significant differences between bus bar based design and PCB based design additionally emphasise the above mentioned advantages, as simply visualised by the contrast between the original application and it's PCB-based Redesign.

Providing the new LXXX 15.00 high-power PCB terminal (Fig. 2), Weidmüller enables the engineer to replace extensive and expensive bus bar constructions up to 150Amps by a compact single component for easy wave soldering, simple integration and fast und safe connection. The features in detail:

- Unique clamping capacity: With its unmatched clamping range, the LXXX 15.0 connects wires up to 50mm2/AWG1 securely to the PCB. Weidmüller's self-securing steel clamping yoke has proven in millions of cases that it is truly 100 per cent maintenance free.

- Protection against incorrect use = functional security: The integrated Wire Guard provides protection against miswiring and eliminates the risk of wires being inserted under the clamping yoke, fusing contact.

Weidmüller's high-performance WEMID insulating material contains neither halogen nor phosphor and is compliant with the strictest environmental standards. The so-called RTI (relative temperature index) of 120°C, the LXXX 15.0 exceeds the maximum continous operating temperature of standard PA (100°C) by 20°K. The benefits: additional performance reserves for the highest level of security due to temperature cycling and overloads.

- Application-Based Design: This transborder perspective of the component directives makes the application approval process quicker and easier. The LXXX 15.0 can be used without any additional covering because of its extended clearance and creepage distances (in accordance with the IEC 61800-5-1 device directive).

- Multiple Marking Options: Labelling options and advantages: individualised (direct printing), flexible (Dekafix marker strips) or cost-efficient (adhesive strips).

Particularly when dealing with power, the top priority is usage and maintenance that is reliable and secure. The test plug (available as an accessory) enables measurement over an extended period of time.

In total, high applicability enables the PCB to also be used in high-current applications for integrated and sustainable systems platforms.

In order to handle this current and voltage level and even the related wire sizes, there is more expertise and competence required than meeting the terminal specifications and component standards.

It is essentially, to avoid mechanical stress to the solder points and the entire circuit board, if the cables connected are finger-thick, but it is even more important, to avoid temperature overload - not only to prevent the device from heat collapse. It is even a question of the reliability and durability (the maximum operating life cycle) due to the so called term of Arrhenius, which proves a reduction of 50 per cent per each temperature rise of 10°C. To put it in another way: An application with a maximum operating temperature rise of 30°C provides double the life time and reliability, compared to a device which indicates 40°C temperature rise under full load.

According to Weidmüller's investigations and experiences in the field of power connectivity, there are several factors influencing the temperature rise of an electrical system: Besides the power loss of the active components and the constructive layout of heat sinks, it is also simple things to consider, such as surface size, cross connection and distance of the wires resp. the power conducting paths in the board or even pin layout, molding and current bar design resp. material of the terminal - the higher the current, the higher the impact.

Last but not least, due to the huge mass of high power components and boards, the solder quality depends strongly on the pin design and the soldering heat profile. The different temperature shapes of a system can easily be determined by thermal imaging (Fig. 3).

It is also important to be aware of the physical phenomenon, that the spot of highest temperature dispense is NOT necessarily the point of heat origin, because the mass and the thermal resistance between the surface of the heat conducting material and the environment determines the relative temperature loss resp. heat sink capability of each spot of the system.

So, if one experiences that a terminal shows the highest share of temperature on the thermal image, the problem is regularly not the terminal, it is only the best heat sink due to the mass and surface of the clamping yoke and the connected wire, which draws the heat out of points of heat origin such as undersized conductor paths or low quality solder connections.

To put it in a nutshell: The latest power PCB technology in combination with high performance connection technology PLUS the experience and expertise concerning special requirements on high currents - this is the key success factor on replacing bulky bus bar constructions in order to save space, production efforts and finally money while maintaining smaller devices at the same or a higher performance level.

DOE gives $8.5 million to grid infrastructure projects !

While not a very sexy topic in realm of politics or green tech news, electrical grid infrastructure is a critical, maybe the critical, component that could make or break a successful U.S. switch to using more renewable energy sources.

Perhaps that's why the Department of Energy announced Tuesday it's giving $8.5 million to four electric grid projects in the final stages of completion.

As part of the Solar Energy Grid Integration Systems (SEGIS) program, from which the money comes, the DOE funds will be matched by private funds from contractors for four chosen projects.

Including the DOE funding, the four projects will total $20 million.

"Projects were selected based on the highest likelihood of commercialization of reliable products that will best enable and accelerate the integration of solar PV technologies into an intelligent electrical grid," according to a statement from the DOE.

New Jersey, which recently garnered attention in August for its Offshore Wind Economic Development Act, is home to two of the DOE-funded projects. That's significant because the biggest criticism of the New Jersey offshore wind push is that the state does not currently have the infrastructure to make offshore wind work, and some fear the cost to update could be passed on to corporate and residential electricity consumers. While this round of DOE funding is directed toward solar infrastructure integration, it could be a signal that the federal government may also be willing to fund similar projects for offshore wind with regard to transmission lines and grid connectors.

Petra Solar South, Public Service Electric & Gas (PSE&G), and the University of Central Florida have partnered to develop modular inverters that are designed to be built and installed with little cost. The line voltage inverters have communications and smart grid capabilities that allow energy generated from a solar panel to be directly integrated into a smart grid system. It's particularly useful for New Jersey, which plans to install more than 200,000 photovoltaic solar panels from Petra Solar onto existing utility poles and tie them directly into the electricity grid.

"The second New Jersey program to get almost $3 million in DOE funding involves the installation of 100-kilowatt Demand Response Inverters (DRI) with circuits designed by Princeton Power. The company claims its inverters, which were derived from military technology, can convert power with up to 98 percent efficiency in some cases. The project partners include First Energy Corp, International Battery, Center for Power Electronics Systems, Process Automation, and Tectonic."

Florida Solar Energy Center of the University of Central Florida, in conjunction with SunEdison and others, has received the DOE funding to implement inverters for both residential and commercial photovoltaic solar systems, and also smart grid power controls.

The fourth project is in Oregon and includes among its partners PV Powered, as well as Portland General Electric. The roughly $2,400,000 in DOE funds will go toward implementing smart grid communication technology, including distribution management systems for utilities that can work with solar energy sources

Electricity use curbed by pricing? Not exactly

A Washington, D.C. program intended to determine the effects of smart meters on household electricity use uncovered habits that could have ramifications in the way electric utilities implement pricing plans to consumers.

Bottom line: socioeconomic status does not matter when it comes to saving energy; most customers with access to smart meters reduce overall electricity use when presented with their habits and a financial incentive to save. Most would also rather curb usage or face high premiums a few times a year during extreme peak events than worry about keeping track of daily peak and off-peak usage hours. So-called peak reductions in summer are greater than those in winter and, not surprisingly, most of those peak summer events occurred when daily temperatures rose, according to the results of the study released Thursday in conjunction with the PowerCentsDC smart meter program.

In addition to smart meters, PowerCentsDC participants with central air-conditioning systems were given smart thermostats that could modify temperature during peak usage events.

The pilot program was conducted by eMeter Strategic Consulting and the Smart Meter Pilot Program in Washington, D.C. with 900 existing Pepco electricity customers from all eight city wards, including low-income customers. The participants were asked to use smart meters and smart thermostats to manage their household electricity use. The group was offered a choice of three pricing plans for the program which began on July 21, 2008, and ran through October 2009.

When asked to name the methods they used toreduce consumption during peak events, 60 percent of participants said turning off appliances, while 59 percent said they adjusted the air-conditioning. Only 25 percent said they adjusted their heating system, but it should be noted that 54 percent of the participants had a heating system powered by natural gas.

"Summer peak reductions were greater than winter, implying more discretionary load," according to the PowerCentsDC Program final report released Thursday.

The extensive program went deeper than just trying to see how consumers could be encouraged to use less electricity during peak loads. It evaluated all manner of variables, including whether consumers generally preferred having an opportunity to curb usage and save money, or would rather pay extra for electricity use at peak usage times. It even determined habits of homeowners versus renters.

All households in the study were given smart meters. Those with central air conditioning systems were also given smart thermostats that could be controlled remotely by Pepco, as well as programmed for desired daily temperature by the consumer. Participants were then given the option to pick from three different pricing plans.

The most popular plan was one in which customers were charged five times the average price during "critical peak pricing" events, which occurred about 60 hours per year, and offered a slightly reduced rate for the remainder of the year.

People seemed more willing to curb electricity use, or face paying an extremely hefty surcharge during peak events a few times a year, rather than curbing electricity on a daily basis during specified peak hours, according to the results of the study.

The second plan was an hourly pricing option that offered peak versus off-peak pricing based on the time of the day electricity was used. The third plan offered rebates to customers who voluntarily curbed their electricity use during peak events.

For all three plans, consumers could choose to allow their smart meters to automatically adjust a home's electricity use when notified of a peak event. Consumers were able to find out ahead of time when peak hours might occur via an automated phone message, e-mail, or text, and choose to reduce consumption during those hours. Participants also received a chart illustrating their usage habits with each monthly electricity bill.

The results of the study found that more than 90 percent of all PowerCentsDC participants ended up saving on their Pepco electricity bills, compared to non-smart meter customers. And 93 percent of participants said they preferred using a smart meter and a peak rate system than Pepco's current rate plan.

"The report will be utilized by the White House as a best practices example for other states considering their own smart-grid deployments, highlighting how utilities and consumers can interact to maximize benefits of energy efficiency and cost savings for all parties," eMeter said in a statement.

The program was conducted by the Smart Meter Pilot Program, a nonprofit organization whose members include the electric utility Pepco, the D.C. Office of the People's Counsel, the D.C. Consumer Utility Board, the International Brotherhood of Electrical Workers Local 1900, and the D.C. Public Service Commission.

"SOUND BULLETS" COULD BLAST SUBS, CANCER

• An ordinary office toy has inspired a whole new acoustic weapon: "sound bullets."
• Sound bullets could destroy submarines and annihilate tumors.
• The damage such concentrated waves of pressure could create would be devastating.

An old toy has inspired a powerful new weapon that could destroy submarines or annihilate tumors.

Using a modified version of Newton's cradle, a series of stainless steel balls suspended by fishing wire, scientists from the California Institute of Technology have created a powerful weapon for soldiers and doctors known as a "sound bullet."

 

 

"The beauty of this system is that it's just a bunch of ball bearings that we control with weights," said Chiara Daraio, a professor at Cal Tech and co-author of a new Proceedings of the National Academy of Sciencesarticle. Yet by varying the pressure on the ball bearings, the scientists can dramatically amplify and focus sound waves to make them "extremely destructive," according to Daraio.

 

Newton's cradle is an old toy, but the Cal Tech scientists, including Alessandro Spadonia, have adapted it for a hot new field of science known as metamaterials, which includes the Harry Potter-style invisibility cloak. Metamaterials are usually difficult and time-consuming to create.

For their study, the researchers lined up 21 rows of stainless steel ball bearings in an area the size and shape of a laptop computer, with weights attached at the ends to vary the pressure on each row. Then the scientists dropped a small ball about eight inches onto the ball bearings. Using a high-speed camera and a pressure sensitive material, the scientists watched the pressure waves focus on a single spot several inches away from the metamaterial.

The simple set up belies the power of the new metamaterial. Not only did the scientists focus all of the sound waves onto one specific area; they also amplified those waves more than 100 times than what any other metamaterial had previously produced. Those numbers could easily go higher, said Daraio.

The sound waves Daraio and Spadonia manipulated were too high pitched for human ears to detect. Properly adapted to audible sound, the new metamaterial could turn a normal sentence into a split second ear drum rupturing explosion.

If these sound bullets were actual bullets, the metamaterial would be like transforming hot lead projectiles into rocket propelled grenades, all converging on one place at one time. The damage such concentrated waves of pressure could create would be devastating.
 

"Like normal bullets, sound bullets can travel through air. Unlike normal bullets, sound bullets can also easily travel through liquids and solids. Sound bullets could be used by the military to create submarine melting waves of pressure or shock waves powerful enough to destroy caves otherwise untouchable by conventional weapons."

Sound bullets won't just destroy large objects. Daraio says that powerful, focused sound waves could obliterate hard kidney stones or destroy cancerous tumors without any damage to surrounding tissue.

Other, less destructive applications are also possible, said Daraio. Focused sound waves could let engineers see weak bridge supports or future potholes in roads.

Military or medical use of the new metamaterial is still years away, said Daraio. Yet the simplicity and effectiveness of the sound bullet makes it a "significant development," according to L.B. Freund, a professor at Brown University who was not involved in the research.

"People have focused sound waves for a long time," said Freund. "But if you want to do anything with a sound wave, what you can do is determined by the intensity of the sound wave."

Now that Daraio and Spadonia have found a new way to create these powerful sound waves, the potential range of applications for sound bullets is huge.

"The research has opened a new way to developed applied devices, and was done by young researchers in a very creative way," said Freund.

 

An electric fuel cell powered by your own body:CHANNEL YOUR PERSONAL POWER

Here’s a new one. An electric fuel cell 

powered by your own body. We’ll take a look, today on 

Engineering Works!

•  Lightweight, compact devices could power medical devices. 

• Eat a Snickers bar to power up.

                                                         These days, everybody’s looking for new sources of electricity. All our portable electronics  -- iPods, cell phones, laptops -- they all need good batteries to keep playing or talking or 

 calculating. The batteries we have really aren’t that good. They’re not much better than the voltaic pile battery Alessandro Volta invented more than 200 years ago.

Engineering researchers are looking into a new power source. They’re looking, well, into themselves. 

 

It’s pretty simple – and complicated, all at the same time. Imagine a small chip – called a biofuel cell – that uses sugar and oxygen to generate electricity. Now, imagine that biofuel cell is implanted in your arm. The oxygen and sugar is in your blood. Can you see it now? Electricity. It’s always there and always being recharged. Running low on power? Grab a Coke or a candy bar. 

The engineers really aren’t interested in a new way for you to power your iPod. Not yet, anyway. They’re looking for lightweight, compact, dependable ways for astronauts to power things like medical sensors in space. Now, they’re getting ready to send one up in a satellite to see how well it does in orbit. No people. Just tiny tanks of sugar and oxygen. The people will come later, they hope.

Well, our iPod sounds like it’s going flat. Guess we need to grab a Snickers bar. See you next time.