![]() ![]() ![]() ![]() ![]() Thus, there is no one-size-fits-all solution. However, the air gap needs to be large enough to exert the desired force on whatever the electro-magnet is used for. The larger distance across the air gap, the weaker the magnetic field (other things being equal). Thus, an electromagnet with a ferro-magnetic core needs an air-gap. Such a geometry provides little useful field outside of the core. HOWEVER, such a geometry is useless as an electromagnet because, apart from leakage, the magnetic field is confined to within the core. These dimensions give what is known as a Brooks coil.įor a ferro-magnetic core, the greatest magnetic field for a given amount of core material is a toroidal geometry. The most efficient shape of the electromechanical actuator must be determined using the dimensions, shape and other characteristics of all of the components involved.įor an air-core solenoid, the geometry that gives the greatest magnetic field for a given quantity of conductor is to have the outer diameter of the coil to be approximately twice the inner diameter, and the cross-section of the coil to be approximately square. In engineering, we try to avoid using the word efficient to describe such things as minimizing cost, environmental impact, size and weight, and depletion of natural resources.įor designing electromechanical systems, efficiency by any definition must be considered as part of a careful analysis of the task being performed. Another possibility would be minimizing the energy used by the system during a period of use. It could also mean minimizing the energy required to perform one actuation. For the case in question, maximizing efficiency may mean minimizing the power required to hold something in place. That definition assumes continuous energy conversion or transfer. To determine what is most efficient, you must first define what is meant by "efficient." In engineering, the primary meaning of efficiency is thermodynamic efficiency, defined as output power divided by input power. Many actuating magnets are designed in a "U" shape with the moving piece (armature) designed so that it closes the "U" shape to form a box. Actuation magnets have an iron path that conducts the flux from end to end except for an air-gap that is closed when the mechanism is actuated. The outside of the magnet is covered by iron that completely covers the top end and the outside leaving only an air-gap around the outside of the bottom. Magnets for picking up scrap have a short core in comparison with diameter and an iron cover. Magnets are usually designed to move some specific mechanism or to pick up scrap steel. The design of a magnet's shape is very much determined by the intended use. Magnetic flux flows much more easily in an iron core than in an air core. There are specific reasons I went with this as opposed to a standard actuator, primarily being that I needed the force to drop off as the magnet stays open.ĭoes it matter if the magnet in question is using an air core, or magnetic core? This electromagnet is intended to push on a permanent magnet. Does it matter if the magnet in question is using an air core or a magnetic core? It would help simplify the selection process.Is there an ideal ratio for the length versus the width of an electromagnet?.The book was originally written in 1948, so it occurs that this information could have since been found false. That said, I've looked online and found professionally made electromagnets that have a greater depth than length. According to Design of Magnets and Electromagnets by T.B Montgomery, though, the most efficient electromagnets are 1.5 times longer than the outside diameter. This would seem to suggest that the shorter the core, the better. It turns out that, no matter the length of the core, the windings will raise ~. I've exprimented various lengths of core, and figured the height of the windings for 6 different gauges of magnet wire based on the maximum current densities (from 14 gauge 20 amperes, to 37 gauge. I've been working on a design for an electromagnet. ![]()
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