An Introduction to Electromagnetics
This article is for mechanical and electrical engineers who have a basic understanding of electromagnetics but fall into these two categories:
- Mechanical engineers who are responsible for integrating electrical systems that they did not design and who are facing challenges and unexpected issues they could not have anticipated—and who also might be wondering what is going wrong in their designs.
- Electrical/electromagnetic engineers who do not understand the landscape of the type of problems that can be solved with off-the-shelf software such as CST Studio Suite in Dassault Systèmes’ SIMULIA.
If you fall into one of these two groups, then you understand the long history of companies and governments adding new criteria, considerations and regulations to the projects that you work on—all of which need to be designed and optimized for.
Often times, it takes a new line of thinking to ensure the quality and safety of people in industries that are challenging the status quo. A perfect example is the mainstream development of electric vehicles for automotive and commercial trucks. Replacing internal combustion engines (ICEs) will have new challenges and new requirements for the safety of passengers and for proper operation at all times. Without a century of history to guide the teams designing these tools, engineers will need to work from first principles.
Imagine you were driving along when suddenly you cannot control your acceleration, and your vehicle races off. Would that scare you?
That scenario is not probable, but as we move to more electronics control in our vehicles, things such as incompatible signals, frequencies and electric currencies could potentially trigger strange events. Engineers having a strong understanding of the possible events that could occur is important for public safety, especially the safety of the people driving these new vehicles.
With massive changes happening in automotive technologies, smart devices and all sorts of other digital devices that impact our day-to-day lives, now is the time for engineers to understand these phenomena, even if they don’t think it applies to them.
Hear that, mechanical engineers? You may need to address electrical concerns as well.
Switching to the topic of electromagnetics, if I asked a five-year-old what a magnet is, they may mention something that sticks to a refrigerator. That is, of course, correct.
Magnetism and the movement of charges and electrons are all tightly integrated. Atomic particles, protons and electrons, have charges to them. Like charges repel, while opposite charges attract. The attraction between two particles of opposite charge is what we recognize as that magnet sticking to the refrigerator. The charges of the refrigerator door due to the alignment of its particle structure, and the charges on the magnet, are attracting each other.
With the refrigerator example, it may not be immediately apparent that magnets and electricity are related because both the magnet and refrigerator are stationary. If you take a magnet and spin it, you will create an electric field. Further, placing a conductor inside the field creates a flow of electricity through the conductor. Alternatively, if you run electricity through a conductor, a magnetic field is created around the conductor. If you run electricity through a conductor coiled around a ferromagnetic material, such as iron, you will create an electromagnet. The reason for coiling the wire is to focus the magnetic field in a particular direction. If you want to pick something straight up with a magnet, it makes sense to have the magnetic field acting in the vertical direction.
Thanks to the relationship between magnetism and electricity, spinning a magnet creates an electric field, which a conductor in the electric field will then create a flow of electricity. All along the length of that flow of electricity, a magnetic field is created. Electricity is the distribution of a magnetic field and a magnetic field is the sign that electricity is present. It’s like the classic chicken or egg question, but with physics.
Today, thanks to the discovery of electricity and the invention of digital devices, we are surrounded by electric and magnetic fields. The overhead power lines that deliver electricity to our communities emit powerful magnetic fields as they push electricity to us.
Your computer and printer, cellphone and TV, washer and dryer, electric stove and microwave, your lights, and alarm clock, and soon your vehicle, are all devices that carry electricity and emit electromagnetic fields. When you plug them in, they complete a circuit and depending on the orientation and design of the circuitry inside, as well as the amount of power each device consumes, they create a different size electric field around them. This is increased in complexity by the electromagnetic wave spectrum. When we consider a field in physics, it is thought of as a fixed area of space. However, when that field begins to move, it becomes a wave. The electromagnetic spectrum is filled with waves, including the visible light we see.
(Image source: Wikipedia, “Electromagnetism.”)
Radio waves, microwaves, visible light, X -rays, and gamma rays are being emitted all around us. This is due to more than a century of mass commercialization of electricity and the last 30 years of digital devices. There isn’t a huge amount of study on the effect of exposure to electromagnetic fields. While we understand exposure to super potent fields and waves is bad, it is not as clear what level of electromagnetic exposure people can have without negative health consequences. The study of this is called bio-electric compatibility.
Electromagnetic compatibility is not limited to interactions with biology. It can also interact with other electronic devices, interrupting signals, exciting natural frequencies to create buzzing noises or otherwise disrupting normal operating conditions. Traditionally, this has been a trial-and-error process when it comes to companies integrating components together into a system.
Today, tools exist to better understand the interactions these components have on each other due to the electromagnetic fields and waves that different components produce.
The methods for hand calculations are better suited for solving algebraic equations than they are for differential equations. Since computers can use numerical techniques to solve differential equations, they are well suited to analyze electromagnetic fields. Software offers engineers powerful methods for visualizing these otherwise invisible fields.
While physical validations through the trial-and-error process are still useful and present in the industry, there are significant drawbacks including but not limited to the fact that physical tests tend to be a go or no-go determination. Either things work, or they do not. Not much insight is gathered.
Secondly, you have to pull together a full physical prototype to have any understanding at all. There is not a strong first pass analysis method since fields are three dimensional and highly influenced by geometry.
This is starting to change. Tools such as the CST Studio Suite offer prediction and visualization capabilities for electromagnetics and allow engineers to efficiently design, analyze and optimize electrical systems while ensuring signal integrity, optimal antenna design and more.
There is a new paradigm emerging in tools for understanding electromagnetic compatibility: signal integrity and biocompatibility, where the traditional methods of trial-and-error have become too costly or slow. More than 90 percent of the innovation in vehicles is related to digital and electronic devices, a trend indicative of where the world of product design is headed in general with the push towards smart devices.
Without a better understanding of electromagnetic fields, staying a leader in your industry will be nearly impossible. It is worth taking the time to review the knowledge, ramifications and especially the tools available that can impact your work.
About the Author
Brandon Donnelly is an engineer. For ten years, he was a simulation specialist and then moved progressively towards helping customers better understand the technologies available. Today, he ensures that those in the truck industry don’t overlook opportunities where CAE tools can help.
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