{"id":27335,"date":"2024-03-14T11:59:39","date_gmt":"2024-03-14T11:59:39","guid":{"rendered":"https:\/\/www.engineernewsnetwork.com\/blog\/?p=27335"},"modified":"2024-03-14T11:59:40","modified_gmt":"2024-03-14T11:59:40","slug":"inner-or-outer-rotor-position-specification-for-miniature-dc-motors","status":"publish","type":"post","link":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/","title":{"rendered":"Inner or outer? Rotor position specification for miniature DC motors"},"content":{"rendered":"\n

To get the most from miniature motion technology, a key design specification is whether to configure the motor with an inner or an outer rotor. This consideration is highly relevant to torque requirements, and it also has an impact on footprint and thermal design. Because of the motor\u2019s vital role in applications ranging from medical devices to drones, it\u2019s beneficial to involve a motion designer that can take the objectives of an original equipment manufacturer (OEM) and customise the solution accordingly.<\/strong><\/p>\n\n\n\n

Like every electric motor, miniature brushed DC motors, as well as their brushless DC (BLDC) counterparts, are based around a rotor and a stator. The stator\u2019s role is to create a magnetic field that interacts with the rotor, which is embedded with magnets. It\u2019s this interaction that causes the rotor to spin, driving the motor\u2019s shaft.<\/p>\n\n\n\n

Most commonly, the rotor is on the interior of the motor and the stator is part of the exterior. Conversely, in an outer rotor design, the rotor surrounds the stator. In this configuration, the motor\u2019s stationary component is on the inside, while the rotating component spins around it.<\/p>\n\n\n\n

For OEM design engineers, this distinction, and the choice between the two designs, is relevant because of the impact the selection has, relative to the output requirements of the given application. The position of the rotor can impact crucial aspects such as torque, inertia and heat dissipation \u2013 attributes that are likely to be critical to the overall performance characteristics of a machine\u2019s design.<\/p>\n\n\n

\n
\"\"<\/a>
A traditional Inner Rotor Motor<\/figcaption><\/figure>\n<\/div>\n\n\n

Torque generation<\/strong><\/p>\n\n\n\n

An outer rotor topology provides increased physical space to enable a higher number of magnetic poles compared to inner rotor technology. Created by the arrangement of magnets or electromagnetic windings, the poles are key, as it\u2019s their interaction with the current supplied to the motor that ultimately generates motion. The higher the pole count, the greater the torque that can be generated, because of the frequency of magnetic interactions per rotation.<\/p>\n\n\n\n

With a rotor around the stator, its larger diameter also contributes to increased leverage. This effect enhances the motor\u2019s ability to exert greater torque, thanks to the larger radius at which the magnetic force is applied.<\/p>\n\n\n\n

OuterMoreover, outer rotor motors can also achieve higher torque density, and more power, than comparative inner rotor motors. For a given power, outer rotor motors have a lower length-to-diameter ratio, which makes them compact and flat in design.<\/p>\n\n\n

\n
\"\"<\/a>
Outer Rotor Motor Construction<\/figcaption><\/figure>\n<\/div>\n\n\n

Responsiveness and efficiency<\/strong><\/p>\n\n\n\n

Conversely, inner rotor motors have lower inertia compared to outer rotor motors, which enables higher acceleration, a faster response, and a lower mechanical time constant. This is possible thanks to the rotor\u2019s smaller mass, as well as its closer proximity to the axis of rotation. When an outer rotor motor design is specified, to combat the inertia, material selection and weight reduction are critical. This design will also need greater attention regarding rotor balancing to reduce noise and vibration, as well as to optimise bearing life.<\/p>\n\n\n\n

Inner rotor motors are also more thermally efficient than their outer rotor counterparts, with less hindrance from the limiting factor of heat accumulation. While the rotor is on the inside, their stator, and hence their windings, are positioned on the outside, enabling easier heat dissipation. In contrast, outer rotor motors, with their internal windings, typically require innovative cooling solutions to maximise operational life.<\/p>\n\n\n\n

With lower inertia and improved thermal management, this also makes inner rotor motors more efficient. Contributing to this, inner rotor designs also usually have a smaller air gap between the stator and rotor. This results in more effective magnetic field interactions, which improves electromagnetic efficiency.<\/p>\n\n\n\n

Real-world applications\u00a0<\/strong><\/p>\n\n\n\n

With inner rotor designs, as the rotating component is enclosed within the stator, this effectively creates a barrier that reduces the exposure of the motor\u2019s internal components to external contaminants. The enclosed design minimises gaps, offering greater sealing potential against particles and moisture. As a result, inner rotor motors are often preferred for applications with the most challenging environmental conditions.<\/p>\n\n\n\n

That said, outer rotor motors can still be sufficiently protected for use in rugged locations and more challenging environments. Consequently, the advantage of their high torque characteristics within a compact footprint, for applications that need relatively low speed, can be leveraged for e-bikes, drones, and surgical robots. Alternatively, inner rotor motors excel in high-speed, lower-torque applications, such as medical devices and industrial tools. <\/p>\n\n\n\n

Although an off-the-shelf motor design might fulfil a design team\u2019s needs, more commonly, some level of customisation is required to optimise characteristics for the given application.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"

To get the most from miniature motion technology, a key design specification is whether to configure the motor with an inner or an outer rotor. This consideration is highly relevant to torque requirements, and it also has an impact on footprint and thermal design. Because of the motor\u2019s vital role in applications ranging from medical …<\/p>\n","protected":false},"author":1,"featured_media":27336,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[105],"tags":[9407,8601],"class_list":["post-27335","post","type-post","status-publish","format-standard","has-post-thumbnail","","category-design","tag-miniature-dc-motors","tag-portescap"],"yoast_head":"\nInner or outer? Rotor position specification for miniature DC motors - Engineer News Network<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Inner or outer? Rotor position specification for miniature DC motors - Engineer News Network\" \/>\n<meta property=\"og:description\" content=\"To get the most from miniature motion technology, a key design specification is whether to configure the motor with an inner or an outer rotor. This consideration is highly relevant to torque requirements, and it also has an impact on footprint and thermal design. Because of the motor\u2019s vital role in applications ranging from medical …\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/\" \/>\n<meta property=\"og:site_name\" content=\"Engineer News Network\" \/>\n<meta property=\"article:published_time\" content=\"2024-03-14T11:59:39+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2024-03-14T11:59:40+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2024\/03\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"813\" \/>\n\t<meta property=\"og:image:height\" content=\"597\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/\"},\"author\":{\"name\":\"admin\",\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/#\\\/schema\\\/person\\\/4477342aea8e299c6a21761e513ea8e1\"},\"headline\":\"Inner or outer? Rotor position specification for miniature DC motors\",\"datePublished\":\"2024-03-14T11:59:39+00:00\",\"dateModified\":\"2024-03-14T11:59:40+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/\"},\"wordCount\":775,\"image\":{\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/wp-content\\\/uploads\\\/2024\\\/03\\\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg\",\"keywords\":[\"miniature DC motors\",\"Portescap\"],\"articleSection\":[\"Design\"],\"inLanguage\":\"en-GB\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/\",\"url\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/\",\"name\":\"Inner or outer? Rotor position specification for miniature DC motors - Engineer News Network\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/wp-content\\\/uploads\\\/2024\\\/03\\\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg\",\"datePublished\":\"2024-03-14T11:59:39+00:00\",\"dateModified\":\"2024-03-14T11:59:40+00:00\",\"author\":{\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/#\\\/schema\\\/person\\\/4477342aea8e299c6a21761e513ea8e1\"},\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/#breadcrumb\"},\"inLanguage\":\"en-GB\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-GB\",\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/#primaryimage\",\"url\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/wp-content\\\/uploads\\\/2024\\\/03\\\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg\",\"contentUrl\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/wp-content\\\/uploads\\\/2024\\\/03\\\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg\",\"width\":813,\"height\":597,\"caption\":\"A traditional Inner Rotor Motor\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Inner or outer? Rotor position specification for miniature DC motors\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/#website\",\"url\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/\",\"name\":\"Engineer News Network\",\"description\":\"The ultimate online news and information resource for today's engineer\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-GB\"},{\"@type\":\"Person\",\"@id\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/#\\\/schema\\\/person\\\/4477342aea8e299c6a21761e513ea8e1\",\"name\":\"admin\",\"url\":\"https:\\\/\\\/www.engineernewsnetwork.com\\\/blog\\\/author\\\/admin\\\/\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Inner or outer? Rotor position specification for miniature DC motors - Engineer News Network","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/","og_locale":"en_GB","og_type":"article","og_title":"Inner or outer? Rotor position specification for miniature DC motors - Engineer News Network","og_description":"To get the most from miniature motion technology, a key design specification is whether to configure the motor with an inner or an outer rotor. This consideration is highly relevant to torque requirements, and it also has an impact on footprint and thermal design. Because of the motor\u2019s vital role in applications ranging from medical …","og_url":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/","og_site_name":"Engineer News Network","article_published_time":"2024-03-14T11:59:39+00:00","article_modified_time":"2024-03-14T11:59:40+00:00","og_image":[{"width":813,"height":597,"url":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2024\/03\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg","type":"image\/jpeg"}],"author":"admin","twitter_card":"summary_large_image","twitter_misc":{"Written by":"admin","Estimated reading time":"4 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/#article","isPartOf":{"@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/"},"author":{"name":"admin","@id":"https:\/\/www.engineernewsnetwork.com\/blog\/#\/schema\/person\/4477342aea8e299c6a21761e513ea8e1"},"headline":"Inner or outer? Rotor position specification for miniature DC motors","datePublished":"2024-03-14T11:59:39+00:00","dateModified":"2024-03-14T11:59:40+00:00","mainEntityOfPage":{"@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/"},"wordCount":775,"image":{"@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/#primaryimage"},"thumbnailUrl":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2024\/03\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg","keywords":["miniature DC motors","Portescap"],"articleSection":["Design"],"inLanguage":"en-GB"},{"@type":"WebPage","@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/","url":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/","name":"Inner or outer? Rotor position specification for miniature DC motors - Engineer News Network","isPartOf":{"@id":"https:\/\/www.engineernewsnetwork.com\/blog\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/#primaryimage"},"image":{"@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/#primaryimage"},"thumbnailUrl":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2024\/03\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg","datePublished":"2024-03-14T11:59:39+00:00","dateModified":"2024-03-14T11:59:40+00:00","author":{"@id":"https:\/\/www.engineernewsnetwork.com\/blog\/#\/schema\/person\/4477342aea8e299c6a21761e513ea8e1"},"breadcrumb":{"@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/"]}]},{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/#primaryimage","url":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2024\/03\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg","contentUrl":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2024\/03\/PORTESCAP134_Tradtional-Inner-Rotor-Motor_Pic-2.jpg","width":813,"height":597,"caption":"A traditional Inner Rotor Motor"},{"@type":"BreadcrumbList","@id":"https:\/\/www.engineernewsnetwork.com\/blog\/inner-or-outer-rotor-position-specification-for-miniature-dc-motors\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.engineernewsnetwork.com\/blog\/"},{"@type":"ListItem","position":2,"name":"Inner or outer? Rotor position specification for miniature DC motors"}]},{"@type":"WebSite","@id":"https:\/\/www.engineernewsnetwork.com\/blog\/#website","url":"https:\/\/www.engineernewsnetwork.com\/blog\/","name":"Engineer News Network","description":"The ultimate online news and information resource for today's engineer","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.engineernewsnetwork.com\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-GB"},{"@type":"Person","@id":"https:\/\/www.engineernewsnetwork.com\/blog\/#\/schema\/person\/4477342aea8e299c6a21761e513ea8e1","name":"admin","url":"https:\/\/www.engineernewsnetwork.com\/blog\/author\/admin\/"}]}},"_links":{"self":[{"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/posts\/27335","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/comments?post=27335"}],"version-history":[{"count":1,"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/posts\/27335\/revisions"}],"predecessor-version":[{"id":27338,"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/posts\/27335\/revisions\/27338"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/media\/27336"}],"wp:attachment":[{"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/media?parent=27335"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/categories?post=27335"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.engineernewsnetwork.com\/blog\/wp-json\/wp\/v2\/tags?post=27335"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}