Monthly Archives: November 2016

The concept of air region in EM Simulation

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In all EM simulation, the empty spaces (or volumes) within a model and around a model are important. This is because we are interested in computing and plotting the magnetic and electric fields in these regions. Imagine a magnet lying on a table, there is magnetic field inside the magnet (of course) but there is also a magnetic field in the air region surrounding the magnet and also in the table. In order to capture these fields, one must model these empty spaces as 3D geometry along with the components of interest.

If you are using EMS for SolidWorks, creating air geometry inside SolidWorks is extremely easy (see video linked below). You first have to create a new part in the assembly you want to simulate. Remember that all EMS models have to be SolidWorks assembly to be simulated. In the new part, you can sketch and extrude any arbitrary shape as long as you make sure that this shape sufficiently encloses all the other parts of the assembly. Next you must use the Cavity feature in SolidWorks to subtract out all the inner components. Now your model is ready for EM simulation (see Figure 1). Please note that you are not just limited to a box region as shown in the figure. For some designs which are cylindrical in nature, it is more appropriate to create a cylindrical air geometry (see Figure 2).Air region in EM Simulation

Figure 1- Air region created around a C core inductor using SolidWorks cavity feature

Air region cylindrical in EM Simulation

Figure 2- One can create a cylindrical air region as well for models that are cylindrical in nature

Video explaining how to create air region in SolidWorks:

When you create the air region, make sure that it is sufficiently big so that the results at the extremities of the air region is negligible compared to the ones closer to the model. For example, plot the magnetic flux density on the boundary faces of the air region and compare those values to the maximum value of the magnetic flux density. Also the magnetic flux density should be fairly uniform in these boundary faces.

This blog post is a part of Learn EMS for SolidWorks series. To learn more about EMS, visit www.emworks.com.

Induction heating – Engineers empower chefs

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About induction heating

Induction heating is a process of heating an electrical conductor (usually ferromagnetic materials and metals) by electromagnetic induction. The heat generated in the conductor is due to the eddy currents induced in the conductor. In the simplest form, an induction heater consists of a coil through which a high frequency AC current is passed. This high frequency AC current causes rapidly alternating magnetic field which then causes eddy currents in the conductor. The eddy currents are responsible for heating the conductor, the higher the resistance to the flow of current, the more the heating. This phenomenon of eddy currents heating the conductor is called Joule effect.

A conducting rod is heated using induction

Figure 1- A conducting rod is heated using induction

One needs to contrast between conduction and induction. In the case of induction heating, the heat is generated inside the object and the object does not need to be in contact with the heat source. Hence induction facilitates rapid heating. There are many applications where induction is used such as induction furnace, induction welding, induction cooking appliances etc. The rest of this article is about induction cooking application.

What is induction cooking?

In the case of induction cooker, a cooking vessel usually made of a ferromagnetic material is heated by induction. Contrast this to the same vessel heated by flame or an electric coil. Induction heating brings about a rapid increase in temperature of the vessel. As shown in figure 2, a coil of copper is placed under the vessel. There is also a layer of ceramic between the coil and the vessel. This is commonly referred to as top plate.induction cooking Elements of induction cooking appliance

Figure 2- Elements of induction cooking appliance

When high frequency AC current is passed through the copper coil, large eddy currents are induced in the vessel. The surface resistance of the vessel heats it rapidly which enables cooking. Now there are choices of the material used for the cooking vessel but it is highly recommended that the vessel be made of a ferromagnetic material like cast iron or some specific grades of stainless steels. It is not recommended to use Aluminum or Copper vessels (you can use Aluminum or Copper with modification to the cooking appliance by including a ferromagnetic disk which functions as a hot plate). The use of ferromagnetic material has 2 advantages –

  1. The electrical resistance is higher than pure conductors and hence the heat produced is more.
  2. The skin depth (more about this in a later blog post) of ferromagnetic material is lower than pure conductors and hence there is more surface resistance resulting in higher joule heating.

Why induction based cooking is attractive?

  1. It is energy efficient. It provides faster and more consistent heating with higher thermal efficiency. According to a technical document from S. Department of Energy (DOE) in 2001, the efficiency of energy transfer for an induction cooker is 84%, versus 74% for a smooth-top non-induction electrical unit.
  2. The heating performance is uniform and compares to a gas burner.
  3. A control system usually shuts down the heating element if the cooking vessel is not present or is not large enough.
  4. They are easy to clean and maintain because the cooking surface is flat and doesn’t get too hot to burn and stick spilled food. Figure 3 shows that heat is produced only in the vessel.

Heat is produced only in the vessel and not in the top plate

Figure 3 – Heat is produced only in the vessel and not in the top plate

Simulation using a standard induction cooker coil arrangement

Figure 4 shows a CAD model of a coil and iron core arrangement which can be used for induction cooking. A simulation was performed using EMS for SolidWorks using AC excitation at 24 KHz. The inductance of the coil was computed and the magnetic flux density was visualized.

CAD model of a typical coil using for induction cooking

Figure 4 – CAD model of a typical coil using for induction cooking

The inductance value calculated by the software was 92.67 micro Henry and compared very well with the laboratory measurement result (93.8 micro Henry). Figure 5 shows the plot of magnetic flux density in the coil and the iron cores.

inductance value

plot of magnetic flux density in the coil and the iron cores

Figure 5 – The plot of magnetic flux density in the coil and the iron cores

Conclusion

It is engineers who gave chefs a perfect solution to an energy efficient cooking appliance. EMS for SolidWorks can help engineers design and simulate various types of induction coil arrangements for cooking application. As it is completely embedded inside SolidWorks, EMS can directly simulate SolidWorks designs thereby avoiding loss of CAD data due to translation. For a full range of applications that EMS can handle, visit www.emworks.com. This blog post was inspired by the excellent work done by a budding fellow engineer, Majdi El Fahem as part of his senior design project.

Embedded Electro-mechanical/ Electro-magnetic (EM) simulation inside Autodesk Inventor

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by Arvind Krishnan, Director of Product Management, EMWorks

What is EM simulation?

Electro-magnetic or EM simulation is the use of computational techniques to determine the electric and magnetic fields in an electric machine or device. EM simulation can give valuable insight to an engineer about his designs. She can obtain engineering parameters like inductance, flux linkage, impedance, Back EMF, Induced voltage, Capacitance, Forces and Torques etc. So engineers who design electrical devices like motors, generators, linear transducers, inductors, actuators, transformers, voice coils, sensors, resistors, insulators, induction heaters etc can benefit largely from EM simulation. Without EM simulation, one would have to resort to costly prototype testing to validate their designs leaving little or no room to optimize and improve the products.

Benefits of EM simulation

EM simulation fits very well into the design process. Companies who use EM simulation are able to create high quality optimized products which make them hypercompetitive in todays market. The rise in popularity of simulation tools have ensured that companies all around the world from industrialized nations of the west to the developing nations of the east have a level playing field. What is more important is that the seamless integration of EM simulation into the product development process have accelerated this trend. Now an engineer can quickly put his concepts and inventions to life my modeling them in 3D CAD packages like Autodesk Inventor. CAD embedded EM simulation packages like EMS for Autodesk Inventor enables them to validate, improve and optimize their design quickly without ever entering a testing laboratory or engaging in a prototype. Further more, EM simulation can be coupled to mechanical and thermal simulations to accurately predict the thermal and mechanical performance of electrical devices. Once the design is accepted, 3D printers bring life to these digital products which can then be tested before they are sent for mass manufacturing. This 3D digital engineering product development process has revolutionized the electrical machines and devices industry. Figure 1 shows a typical product development workflow using Autodesk Inventor and EMS for Inventor.

the-product-development-workflow-inside-autodesk-inventor

Figure 1 – The product development workflow inside Autodesk Inventor

Benefits of integration inside Autodesk Inventor

Autodesk Inventor is a very popular 3D CAD platform for engineers in the field of electrical machines and devices. EMS for Autodesk Inventor enables engineers to incorporate EM simulation into their product development process. Integration inside Autodesk Inventor brings in the following advantages –

  1. Direct use of 3D CAD model for simulation. No need to export CAD geometry for simulation purpose thereby maintaining the integrity of the design.
  2. Enable simulation based product development where simulation feeds into the 3D design allowing engineers to make drastic changes to their initial design concept. All of these are possible without ever leaving Autodesk Inventor platform.
  3. The learning curve for engineers to learn and use simulation is shortened because they don’t have to learn a new program and a new interface. They can work inside their familiar Autodesk Inventor interface to perform their EM simulations.

Application areas

EM simulation has many applications areas ranging from small electrical machines to large transformers. These devices can use DC, AC or other kinds of excitation. The applications of electromagnetics are so vast that it will be a great injustice to categorize them as I have attempted here for the sake of brevity. I admit that there are many devices and applications that overlap these categories.

  1. Rotary and linear actuators, Motors and Generators
  2. Transformers, Inductors
  3. Insulators, high power switches, bus bar networks, Induction heaters
  4. Sensors, motion controllers and measurement devices
  5. Permanent magnet based devices, magnet arrays, magnetic levitation

EMS for Inventor can calculate the magnetic field inside a motor and also the cogging torque

Figure 2 – EMS for Inventor can calculate the magnetic field inside a motor and also the cogging torque

EMS for Inventor can help visualize the losses in the core of a transformer

Figure 3 – EMS for Inventor can help visualize the losses in the core of a transformer

Conclusion

EMS for Autodesk Inventor is a 3D field simulation software that is embedded inside Autodesk Inventor. It can perform both electric and magnetic simulation with AC, DC and transient excitations. EMS has powerful Multiphysics capability to do coupled EM, mechanical and thermal simulation. EMS customers use the product to design solenoids, motors, transformers, magnet arrays, high voltage insulators, electric generators, speed sensors, induction heaters, bio-medical actuators and magnetizers. Autodesk Inventor customers can download a full trial version of EMS in the Autodesk App store. For more information on EMS, visit www.emworks.com.