Category Archives: Coils

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.

Metal Detector Explained

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Electromagnetics and its impact

It is amazing how many applications the theory of Electromagnetics has in today’s world. If Faraday and Maxwell have a chance to view the number of devices that makes use of their discovery, they will be simply blown away. Simply by the impact of their discovery in today’s world, many scientist believe that these two men were probably the most important people to have inhabited the Earth since 1600. You don’t have to take my word, you can read about their impact here.

In this short note, I want to explain the concept of metal detector and how it uses Electromagnetic principles for its functioning. More important we will see how an electromagnetic software like EMS can help companies that design and build Metal Detectors.

Concept of modern metal detectors

The principle of metal detector is quite simple and as the name suggest it is a device that can identify if metals are present say in hard to find places like under the soil, inside rocks etc. It finds its use in detecting things from land mines (really a wonderful use of metal detector which has saved many thousands of life and is still continuing to save) to gold mines.

Most metal detector have 2 coils – one coil carries alternating current usually at very high frequency (1-10 KHz) and other coil acts like a receiver. The excited coil generates a magnetic field and this induces a small amount of current in the receiver coil. This current (also called as Induced current or Eddy current) is known and calibrated. Now when you take this arrangement near a metallic (or ferromagnetic) substance, two things happen. First, the excited coil also induces an eddy current in the metallic (or ferromagnetic) substance. This eddy current produces its own magnetic field that opposes the magnetic field produced by the coils. This causes the eddy current in the receiver coil to drop. A sensor senses this drop in eddy current from the expected value and gives a signal indicating the presence of a metallic substance. In the figure below, the orange coil is the excited coil and the green one is the receiver coil. High frequency AC current is circulated in the orange coil and the eddy currents induced in the green coil in the absence of any metallic substance is calibrated.

Simple arrangement of coils in a metal detectorFigure1 – Simple arrangement of coils in a metal detector

Role of SolidWorks and EMS in designing a metal detector

For an engineer, several design factors need to be considered before this concept can be made into a functional product and that is where SolidWorks CAD and EMS Simulation software can play a vital role. Let us look at some of them.

  1. What is the right size of the coil?
  2. What frequency and magnitude of AC current should be applied?
  3. What is the induced current in the receiver coil under ideal (no metal in the vicinity) conditions?
  4. How can I package the entire arrangement into a product?

Together with SolidWorks, the EMS product can help a designer answer all the above questions. Once a concept coil is arrived at, it can be tested virtually using EMS to visualize all the engineering parameters. For example, engineers can visualize the magnetic flux density in the coils as shown in the figure.

Metal Detector - EMS can plot the magnetic flux density in the coils

 Figure 2 – EMS can plot the magnetic flux density in the coils

EMS product will also give you the value of the induced current in the receiver coil.

Plot of the eddy current density in the receiver coil

Figure 3 – Plot of the eddy current density in the receiver coil

Most importantly you can model different hypothetical situations like what happens to the induced current in the receiver coil when you come across a metallic object at a particular distance from the coil. EMS can also compare the induced eddy currents in the receiver coil when a metallic part is present and when it is not present. This way the product can be perfected before a prototype is made and tested.

Metal detactor - EMS plots with the presence of a metallic part

Figure 4 – EMS plots with the presence of a metallic part

Metal detactor - Compare the eddy currents induced in the presence of a metallic part with the ideal cas

Figure 5 – Compare the eddy currents induced in the presence of a metallic part with the ideal case

Advantages of this approach

The advantage of using Simulation in product development is well studied and many engineers have got impressive results by using this approach. First of all the time taken to bring a concept to the shelf is greatly reduced. Next, the cost of product development is lower as the number of prototypes required to perfect the product is greatly reduced. For most companies which uses this approach, their first prototype with some minor tweaks invariably becomes their final product. Finally, this approach enables innovation in product development as many what-if scenarios which an engineer conceives can be tested thoroughly and the best design can be chosen.

EMS for SolidWorks

EMS for SolidWorks is the first and only completely embedded Gold Certified software for SolidWorks which helps SolidWorks users study their magnetic, electric and electromagnetic designs seamlessly. It can utilize the geometry created using SolidWorks directly for simulation. Its user interface emulates SolidWorks and hence there is no learning curve associated with the EMS software for SolidWorks users. Please click here to try out EMS for SolidWorks and see how it can help you design better products. For more information visit www.emworks.com.

 

 

 

What is Transient Magnetic Analysis?

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Transient Magnetic, is the study of magnetic fields due to time varying currents, typically caused by surges in currents. Similar to Magnetostatic and AC Magnetic, Maxwell’s displacement current that couples the electric and magnetic fields is assumed to be null.In Transient Magnetic analysis, the Gauss’s law for magnetism, i.e. divergence of magnetic flux density is null, and Faraday’s law,, i.e. the induced electromotive force (emf) in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit, are invoked to compute the magnetic field and its related quantities due to permanent magnets and time varying electric currents and voltages. It has many practical applications, including:• Switch on/off modes and failures in power electronic devices
• Saturation in steel cores
• NDT and NDE
• Inductive heating and hardening
• Induction machines
• Levitators
• Motors and generators
• Actuators
• Loud speakers
• Alternators

New article about inductive noise problems

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3D FEA Software Solves Tough Inductive Noise Problems
by Peter Markowski, Envelope Power, Ansonia, Conn.
A previous article on 3D electromagnetic finite element analysis (FEA) software explained how a new generation
of these tools, which includes EMS from EMworks, can be used for optimization of high-frequency transformer
design (see the reference.) In this article, I would like to show how the same software can help to solve difficult
layout problems in electronics, especially power electronics.
Switched-mode power supplies are notorious for hard-to-eliminate noise problems simply because we cannot
completely avoid proximity of high-power switching circuits and sensitive controls. Good engineering practices
such as minimizing high-frequency current loops and voltage surfaces, perpendicular arrangement of potential
source-target sets and using large copper planes for shielding are naturally a must. But without any way of
quantifying problematic phenomena it is impossible to know if we are pushing our luck and if we did the best we
could within the given constraints. In the end, we have to make a choice between unnecessarily conservative
designs and risking costly, time consuming (and stressful!) fixing of prototypes.

To read more, http://www.emworks.com/ckfinder/userfiles/files/design_EnvelopePower.pdf

New generation of 3D electromagnetic

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New generation of 3D electromagnetic finite element analysis software with breakthrough simplicity facilitates magnetic component design

By Peter Markowski, Envelope Power, Ansonia, Conn.

Multiple layers of conductors in transformers can increase copper losses many times due to the proximity effects if the conductor thickness is higher than 0.3 of the skin depth. Traditionally used Dowell’s curves are accurate only in some geometrical arrangements. New generation of Finite Element Analysis software like EMS simulates high frequency phenomenon with much higher accuracy and is easy to use.

To read the full article, please visit

http://www.emworks.com/ckfinder/userfiles/files/Peter_markowski-Magnetic-component-design.pdf

 

A Spaceclaim®-embedded Multiphysics Simulation Package

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MONTREAL (September 25, 2014) – EMWorks Inc. announces the launch of its multi-physics simulation package SimClaim which is fully embedded in Ansys SpaceClaim®, formerly SpaceClaim, Engineer®.  Based on the powerful finite element method, SimClaim brings the company’s proven simulation technology to the widest base of mechanical, electrical and electromechanical designers seeking to validate and optimize their electrical, thermal, and structural designs all within the SpaceClaim environment. “We are pleased to have partnered with SpaceClaim to bring this all important multi-physics simulation technology to the SpaceClaim user community. The support we received from SpaceClaim over the last couple of years has been instrumental in accomplishing this important milestone for our company” said Dr. Ammar Kouki, Vice-President of EMWorks. He added “Ansys SpaceClaim®, is an extremely powerful 3D direct modeling software package that eliminates CAD worries for designers. Direct modeling is dramatically different from the traditional CAD software because it allows the user to directly access the model without even knowing its history. SimClaim leverages this power to enable designers and CAE specialists to carry out conceptual analysis inside SpaceClaim in record time without needing to be CAD experts. CAD experts on the other hand, will find that the SpaceClaim-SimClaim combination is hard to beat when it comes to design validation through simulation given the speed and the highly efficient workflow that this combination offers.”

Electromechanical devices in EMS?

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Electromechanical, electromagnetic, and power electronics devices can readily be studied using EMS. Electromagnetic behaviour could also be investigated with EMS. Below is sample list of devices and applications classified by areas:

Electromechanical
• Motors and generators
• Linear and rotational actuators
• Relays
• MEMS
• Magnetic recording heads
• Magnetic levitation
• Solenoids
• Loud speakers
• Electromagnetic Brakes and Clutches
• Alternators
• Magnetic bearings

Electromagnetic
• Coils
• Permanent magnets
• Sensors
• NDT, NDE
• High power
• High voltage
• PCBs
• MRI Magnets
• Induction heating
• Bushings
• Switchgear
• Cables

Power electronics
• Transformers
• Inverters
• Converters
• Bus bars
• Inductors

Electromagnetic behavior
• Insulation studies
• Electrostatic discharge
• Electromagnetic shielding
• EMI/EMC
• Electromagnetic exposure