Smog Alert

The worldwide push to increase electric motor efficiency that I spoke of in my last blog has some major implications for OEMs that incorporate motors in their products. For OEM's using induction motors, achieving the required IE3 efficiency requirements may mean adding electronics where none had been employed before. All the major semiconductor manufacturers have jumped into this space with components and processors to implement V/F or Field Oriented control inverters. Drive manufacturers, too have off the shelf drives to offer.

Texas Instruments
Infineon
ST Microelectronics

However, the OEM that is incorporating inverters in their product for the first time must address a problem they may not have had before; electromagnetic interference or EMI. All conventional inverter technologies control the motor by chopping the voltage to the motor stator into a 4Khz to 20Khz pulse width modulated square wave (PWM). One side effect of PWM is that the voltage to and on the stator now has high frequency harmonics that extend well in the radio spectrum. We can think of this as a radio frequency smog raising the noise level of the radio spectrum and making it more difficult for radio based communication to occur.

                          Motor Voltage Spectrum: Conventional Drive

If not constrained, this energy can appear on the motor leads, the power leads into the inverter and even on nearby conductive or magnetic structures that resonate at the harmonic frequencies. Industrial drive manufacturers and system integrators have dealt with this problem for years and have developed a portfolio of tools, techniques and products to solve EMI problems, typically on a case by case basis. However, for the OEM new to inverter development, these solutions may be too costly or too application specific. While the basics of EMI mitigation are the same for the industrial drive and a dishwasher, the business constraints of cost, size and repeat-ability are worlds apart.

At Digital Power Engineering, we had EMI in mind when we developed our Resonant Field Exciter technology (patent pending). Our EMI mitigation approach is to eliminate the problem, or at least make it a lot easier, by not producing the high frequency harmonics in the first place. By using a wound field synchronous motor with a Resonant Field Exciter providing the rotor field energy, the stator voltage need not be pulse width modulated, resulting in a much cleaner EMI excitation spectrum.

                              Motor Voltage Spectrum: WSM with RFE

For applications that turn at a constant, grid frequency related speed, using RFE technology means there is no inverter at all and the EMI footprint is little different than the original induction motor. For applications that are either driven from a DC source or need to be variable speed, the electronics between the source and the motor stator only steer, or commutate, the source power into the motor leads in sync with the motor rotation with no PWM. There is still power switching occurring, but it is at the rotor pole speed, which is typically less than 400Hz and usually 50 or 60Hz.

As a result, EMI mitigation, if required at all, is not only much simpler, smaller and less costly, but more effective over a broader range of installations and environments.

For more information on DPE's Resonant Field Exciter technology drop me an email at solutions@gboxllc.com or visit our website at www.digitalpowerengineering.com.

Staying the Course to a More Efficient Future

A few days ago, I posted a link on Linkedin to a recent IEEE article on U.S. electricity demand ( http://spectrum.ieee.org/energywise/energy/environment/us-electricity-demand-flat-since-2007/ ).  Domestic electricity per capita has been flat since 2007. Much of this is attributed to energy efficiency efforts, including legislation that raised the bar on acceptable, minimum efficiency levels, including minimum efficiency of the largest consumer of electricity in America; electric motors.

The International Electrotechnical Commission (IEC), an international, non-government, consensus based standards  organization founded in 1906, has established four levels of motor efficiency to date.

Level IE1 was pretty much the worldwide de-facto standard for motors operating under 690V around 1990. In 1992, the U.S led the way by adopting IE2, effective in 1997. Followed, albeit slowly, by the rest of the world. By 2013 most of the world had adopted IE2.

Almost everyone in the U.S. is aware that legislation in 2007 raised electric lighting efficiency standards, ushering in the era of CFC and LED lighting, but few know that the same legislation raised the bar again on electric motor efficiency, to the IE3 level, effective in 2010. This time the world was quicker to follow. By 2017 the IE3 minimum efficiency standard will be the law of the land for new motors manufactured almost worldwide.

At the moment, there is no legislation in process anywhere in the world to implement IE4. At least not yet. But there it sits as the "holy grail" of motor efficiency. Many OEM's that use IE2 motors in their products aren't waiting for legislation. In the pump, compressor or HVAC worlds IE4 provides a significant competitive advantage over the IE2 motors they now have to design out. As long as they have to pull out a white sheet of paper, they might as well go IE4 if they can.

But IE4 technology can be expensive. Induction motor technology alone can't get there without adding electronic drives, and not every induction motor can be driven by an electronic drive. Permanent magnet technologies also need drives and have the hidden variable cost and long supply chain of rare earth magnets. Switch reluctance technology is so different from conventional motor and drive manufacturing that a new manufacturing infrastructure must be built to provide them in volume, and they can be noisy.

At the Motor and Drive 2015 conference in Orlando in January, we at Digital Power Engineering introduced another solution. A technology that takes a motor configuration that's been around for 120 years and is the electric motor of choice above 400 HP, and makes it practical at low HP as a motor that exceeds IE4 efficiency, has no magnets, requires no drive for single speed operation and is compatible with contemporary motor manufacturing. If you or anyone you know uses a motor above 200 watts in their product, they may already know about the need to shift to IE3. Have them drop me an email at solutions@gboxllc.com and let's start the conversation about an accessible IE4 solution that can provide them a significant competitive advantage.

Beyond Tesla

Nicola Tesla was a visionary. In an era dominated by steam engines he envisioned what today we would call a disruptive technology. His AC power distribution system and induction motor ushered in the 20th century, warts and all. Fast foward to 2012, 117 years after Tesla and Westinghouse first harnessed Niagra and we find we can still improve. 60% of the electricity in the United States is consumed by electric motors running at 60 to 70% effeciency. Tesla didn't have the power electronics, materials and tools we have today; but we do. By applying these tools we can increase grid to motor shaft effeciency up to 90% and add unprecedented functionality. That is the mission of Software Defined Power.

While we don't envision our mission quite as disruptive as Tesla's, we do view it as evolutionary. If it moves, we will make it more effecient and more functional. We do this by re-engineering the system piece by piece with the goal of having each piece functioning optimally. This applies not only to induction motor or DC motor systems but also to pneumatic, hydraulic and engine driven mechanical systems.

Challenge us. Give us a call and see what we can do.

Engineering is All About Challenges.

The recent dust up over repealing the 2007 light bulb energy standards got me thinking. I’ve been in engineering for over 35 years now, but I really started that journey at age 6 watching the attempted launch of Vanguard TV3 on the family’s tiny black and white TV screen. Right then, I was captured by the challenge of “How can this be made to work?” Although I didn’t realize it then, that was when I became an engineer. By the time I graduated from college the space program had wound down but the first “oil crisis” was upon us and the new challenge was energy. I gravitated to power electronics and have been involved with the challenges of converting electrical energy from one form to another ever since.

Many of the challenges we face as engineers are market driven such as reducing the life cycle cost of equipment or redesigning obsolete equipment, but some are the result of the broader goals of society to improve life. The goals of urban sanitation in the late 19^th century and auto safety of the late 20^th century both come to mind.

The 2007 energy legislation set several goals beyond light bulbs, such as electric motor and appliance efficiency. All of these challenges triggered development of solutions, much of it here in the United States, which continue today. They are already having the intended effect of improving overall efficiency.

Rolling back even the lighting efficiency standards would be like deciding we could get by without seatbelts or baby car seats. In 12 years we overcame the Vanguard failure to land men on the moon; we can build a better light bulb.

My message to our government representatives is; bring on the challenges and set or raise the bar. The only thing you can’t do is violate the laws of physics.

Engineers meet challenges; it’s what we do.

Japan, Energy and Infrastructure

Like a lot of people, I've been following the events unfolding in Japan after the earthquake as well as the worldwide reaction and I can't help putting my engineering hat on. I was in college at UCLA when the now damaged Fukushima nuclear plant was under construction. Coincidently at the time, the United States was also going through the first "energy crises" with high gas prices brought on by suppliers in the Middle East. The UCLA engineering school quickly put together classes and seminars on energy topics, including understanding how energy was then produced,  future supplies, efficiency and even renewable energy. As a student, it was clear to me then that this had to be addressed by my generation. 


Fast forward 38 years. The verdict on our accomplishments is mixed. Yes, we did make improvements in efficiency and some improvements in supply but little progress toward sustainable energy. We basically still get all our energy the same way the cave man did; we burn stuff. Back then it was wood, today it's burning fossil fuels or a hot pile of decaying rocks. There are other ways to extract energy, particularly chemically as is done in biology, or fusion which is how the sun operates. We touched on that in those seminars 38 years ago but for various reasons never throughly pursued them.


In my opinion, we failed miserably on another issue that was obvious back then; infrastructure. The Fukushima complex is almost 40 years old. Why was it still operating? We don't even keep sports stadiums that long! An entire generation of engineers has had the opportunity to improve on that basic design yet it didn't happen. Here in the US, we haven't built a new nuclear power plant since the '70's. Fortunately, the Navy continued using nuclear energy, so design improvements have been made, but we haven't applied them to replacing these old power plants. Think about it. The next generation will be the most energy dependent generation ever but the foundation of their supply would have been built by their grandparents. 


Infrastructure does not last forever.

Erland Persson

On February 22  the world lost a true genius. My mentor and friend, Erland Persson passed away. I worked for Erland back in the early ‘80’s and it is he who taught me the basics of motion control and encouraged in me the confidence, optimism  and sheer love of engineering that still excites me today.

My job interview with Erland for an R&D position at Electro Craft in Hopkins, MN 30 years ago was a turning point for me. Right from the start we discovered common ground in music, science, engineering and even history. That lunch meeting was both the longest and shortest interview of my life. Long in that it lasted all afternoon, short in that it flew by.

At EC, Erland encouraged me to try my wings as an engineering manager (I wasn’t any good at it). At the end of the day we would gather in his office and ponder “What if”, usually regarding some engineering problem we were facing, but often we would drift into solving other problems or even dreaming up new products. At the start of my stint at Electrocraft, he would encourage me to not be so silent, by the end of my tenure there; I was confidently presenting papers at conferences and dealing with customers and staff alike. Somewhere there is a picture of Erland, myself and other young Electrocraft engineers on the beach in Santa Barbara CA. We had gone there to visit a sister division, Renco, and it became a true bonding event for the team.

We were all caught up in the recession of 1986 when Electrocraft management decided to close the R&D department. To his credit, Erland used his extensive contacts in the industry to provide a steady parade of what turned out to be potential employers through the facility, and most of the staff quickly found employment. I had gained enough confidence to strike out on my own, at least for a while, discovering to my surprise that I actually could make it and support my family (and this was pre internet!). I’ve always felt I’ve had Erland at my back.

Erland also struck out on his own at that point, and we continued to collaborate on projects for the next 20 years. With his help, we demystified motion control for a variety of clients and came up with some pretty unique solutions.

Then in 2006, I decided to go on my own full time. I called Erland to tell him the news, he told me he was winding down from consulting and we set up a lunch date. The morning of the meeting, he called to apologize that he had to fly to Detroit to meet a client and couldn’t make it. I said “But aren’t you now retired?”. He replied “yes, but they need me”. That was the essential Erland.

I ran into him once more, at an IEEE Twin Cities banquet a few years ago. He announced to me there that he was really hanging it up. I’m not sure I believed him until I heard that he didn’t renew the Magnetic Finite Element software he had been using. Then I knew he was really retiring.

Now I’ve been on my own full time for almost 5 years and have weathered the worst recession in 80 years, unscathed.

I said earlier I’ve always felt Erland was at my back

He still is.

Gary Box

www.gboxllc.com

www.softwaredefinedpower.com

Comfort Zone

A lot of people do not operate well when they are out of their comfort zone. The same is true for companies. An organization that has been designing and building analog based power conversion equipment may be forced out of their comfort zone when a customer needs visibility into the equipment via CAN or some other digital protocol. By switching to an all digital control scheme, this form of inflexibility can be overcome. However, the very concept of switching from analog to digital control may be daunting. A similar, even more basic, disconnect occurs when a primarily mechanical company takes on electronic control.

At GBOX LLC we have been straddling the fence between power electronics and embedded control for 30 years. We understand the trade offs and what can be done. More importantly, we know what can't be done.

In the coming weeks, we will be rolling out a unified concept for bringing intelligence to power conversion. Stay tuned as we tackle some new but tough applications.