{"id":44,"date":"2016-06-28T14:22:59","date_gmt":"2016-06-28T14:22:59","guid":{"rendered":"http:\/\/18.219.27.21\/?p=44"},"modified":"2018-02-07T20:47:30","modified_gmt":"2018-02-08T01:47:30","slug":"3-key-parameters-to-consider-when-choosing-a-permanent-magnet","status":"publish","type":"post","link":"https:\/\/www.arnoldmagnetics.com\/blog\/3-key-parameters-to-consider-when-choosing-a-permanent-magnet\/","title":{"rendered":"3 Key Parameters to Consider When Choosing a Permanent Magnet"},"content":{"rendered":"
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Every type of permanent magnet has a unique set of characteristics that can affect how is performs in various applications.\u00a0When evaluating magnet options for your project, pay attention to the following:<\/p>\n

1. Temperature<\/h2>\n

One of the most important parameters to consider when choosing a permanent magnet is the temperature of use. As one might imagine, the magnetic field is not constant; it changes with temperature, getting either stronger or weaker. The figure below shows the usable temperature range for each of the five commercially available materials. Conveniently, most applications utilize magnets between -40\u00b0C and 150\u00b0C, and all listed materials are usable within that range.<\/p>\n

\"\"<\/p>\n

Because of their low cost, ferrite (hard ferrite, ceramic) magnets are still widely used.\u00a0 Note however, that ferrite magnets lose 25% of their flux output when heated from 20 to 150 \u00b0C.\u00a0 They also have relatively low energy products, typically 10% of rare earth magnets. So where device size and weight are important, such as hard disk drives and portable electronics (e.g. cell phones, hearing aids), rare earth magnets are necessary.<\/p>\n

2. Availability<\/h2>\n

Issues of raw material price and availability are at the core of today\u2019s discussion on permanent magnets.\u00a0These factors are influenced by the general availability of the raw materials, geographic distribution, ease of recovery from mined ore, and open market trading. Of all the elements used in magnetic materials, rare earth elements have been the most problematic based on geographic limitations on sourcing.\u00a0China still produces 90 percent of the rare earth oxides used each year and more than 95 percent of the rare earth metals and alloys.\u00a0China also produces and consumes 80 percent of all permanent magnets.\u00a0There is inconsequential production of\u00a0neodymium-iron-boron (NdFeB)<\/a>\u00a0in the US.\u00a0One alternative to neodymium magnets is\u00a0samarium cobalt (SmCo)<\/a>, which has fewer sourcing limitations and performs better in higher temperature applications.<\/p>\n

3. Magnetic Output<\/h2>\n

How strong a magnet is can be quantified by one of two key metrics.\u00a0The first is residual induction,\u00a0BR<\/sub><\/em>.\u00a0If a permanent magnet is placed on a steel block, the force required to remove the magnet from the block is proportional to\u00a0BR<\/sub><\/em>.\u00a0BR<\/sub><\/em>\u00a0is one of the magnet characteristics published by magnet producers.<\/p>\n

The second key metric is maximum energy product,\u00a0(BH)MAX<\/sub><\/em>. Maximum energy product is useful in calculating performance of motors.\u00a0(BH)MAX<\/sub><\/em>\u00a0is proportional to\u00a0BR<\/sub><\/em>2<\/sup>. Each type of device benefits especially from either\u00a0B<\/strong>\u00a0(that is,\u00a0BR<\/sub><\/em>) or\u00a0B2<\/sup><\/strong>\u00a0(that is,(BH)MAX<\/sub>\u00a0or BR<\/sub><\/em>2<\/sup>) as described in this table of applications.<\/p>\n\n\n\n\n\n\n\n
General Description<\/strong><\/td>\nPhysical Laws<\/strong><\/td>\nSystem Function
\nProportional to<\/strong><\/td>\n		Application Examples<\/strong><\/td>\n<\/tr>\n
Conversion of mechanical energy<\/td>\nFaraday’s Law<\/td>\nB<\/strong><\/td>\nMicrophone
\nAlternators, Generators
\nMagneto
\nTorque Transmitters<\/td>\n<\/tr>\n
Magneto-static field
\nto mechanical work<\/td>\n		Coulomb’s Law<\/td>\nB2<\/sup><\/strong><\/td>\nCompass
\nReed Switches
\nTorque Coupling (synchronous)
\nMagnetic Separators
\nHolding (attachment) Systems
\nMagnetic Conveyors
\nMagnetic Bearings<\/td>\n<\/tr>\n
Interaction between current and magnetic flux<\/td>\nLorentz Force Law<\/td>\nB<\/strong><\/td>\nMotors: DC, BLDC, Synchronous,
\nStepping, Linear, Moving Coil
\nLoudspeakers, Headphones
\nHDD Voice coil motors
\nGeophones
\nPhonograph pickups
\nElectrical measuring instruments<\/td>\n<\/tr>\n
Magnetic Field
\nFocusing Systems<\/td>\n		Lorentz forces on free charges<\/td>\nB<\/strong><\/td>\nDipoles, Quadrupoles
\nUndulators, Wigglers
\nMagnetrons, TWTs
\nMass Spectrometers
\nNMR devices<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n


\n<\/span>Read our in-depth article,\u00a0Permanent Magnets in a Changing World Market<\/a>.<\/p>\n

Download our technical note for advice on choosing the right magnetic material here<\/a>.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Every type of permanent magnet has a unique set of characteristics that can affect how is performs in various applications.\u00a0When evaluating magnet options for your project, pay attention to the […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"advgb_blocks_editor_width":"","advgb_blocks_columns_visual_guide":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-44","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":[],"yoast_head":"\n3 Key Parameters to Consider When Choosing a Permanent Magnet | Arnold Magnetic Technologies<\/title>\n<meta name=\"description\" content=\"Every type of permanent magnet has a unique set of characteristics that can affect how is performs in various applications. 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