{"id":10740,"date":"2017-12-06T13:00:07","date_gmt":"2017-12-06T21:00:07","guid":{"rendered":"http:\/\/www.palada.net\/index.php\/2017\/12\/06\/news-4512\/"},"modified":"2017-12-06T13:00:07","modified_gmt":"2017-12-06T21:00:07","slug":"news-4512","status":"publish","type":"post","link":"https:\/\/www.palada.net\/index.php\/2017\/12\/06\/news-4512\/","title":{"rendered":"3 safety measures for motors with individual power factor correction"},"content":{"rendered":"<p><strong>Credit to Author: Jerome Guillet| Date: Wed, 06 Dec 2017 20:51:18 +0000<\/strong><\/p>\n<p>In the continuity of the previous article on <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly9ibG9nLnNjaG5laWRlci1lbGVjdHJpYy5jb20vc2VydmljZXMvMjAxNy8xMC8wMy80MjAxMy8%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">5 Steps for Efficient Motor Management Design<\/a>, we tackle <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LWNhdGVnb3J5LzQzMDAtcG93ZXItcXVhbGl0eS1hbmQtcG93ZXItZmFjdG9yLWNvcnJlY3Rpb24%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">power quality<\/a> domain and raise awareness on a particular case of motors with individual <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LWNhdGVnb3J5LzQzMDAtcG93ZXItcXVhbGl0eS1hbmQtcG93ZXItZmFjdG9yLWNvcnJlY3Rpb24%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">power factor correction<\/a> (PFC) capacitors.<\/p>\n<p>Whether <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LXJhbmdlLXByZXNlbnRhdGlvbi85ODgtbW90b3JwYWN0P3BhcmVudC1jYXRlZ29yeS1pZD0zNTAwJmFtcDtwYXJlbnQtc3ViY2F0ZWdvcnktaWQ9MzUxMA%3D%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">direct on line<\/a> (DOL) or with a motor starter (<a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LXJhbmdlLXByZXNlbnRhdGlvbi85ODgtbW90b3JwYWN0P3BhcmVudC1jYXRlZ29yeS1pZD0zNTAwJmFtcDtwYXJlbnQtc3ViY2F0ZWdvcnktaWQ9MzUxMA%3D%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">auto-transformer<\/a>, <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LXJhbmdlLXByZXNlbnRhdGlvbi85ODgtbW90b3JwYWN0P3BhcmVudC1jYXRlZ29yeS1pZD0zNTAwJmFtcDtwYXJlbnQtc3ViY2F0ZWdvcnktaWQ9MzUxMA%3D%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">soft-starter<\/a>, <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LXJhbmdlLXByZXNlbnRhdGlvbi85ODgtbW90b3JwYWN0P3BhcmVudC1jYXRlZ29yeS1pZD0zNTAwJmFtcDtwYXJlbnQtc3ViY2F0ZWdvcnktaWQ9MzUxMA%3D%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">variable speed drive<\/a>), a motor can be individually paired with dedicated capacitor unit to fulfill installation power factor objectives and ensure <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LWNhdGVnb3J5LzQzMDAtcG93ZXItcXVhbGl0eS1hbmQtcG93ZXItZmFjdG9yLWNvcnJlY3Rpb24%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">power quality<\/a>.<\/p>\n<p>Usually not well understood, capacitor protection is often underestimated. Several phenomena have to be considered in order to design an optimum protection and guarantee the safety of people and goods:<\/p>\n<ul>\n<li>capacitor internal fault and failure mode<\/li>\n<li>inrush current,<\/li>\n<li>auto-excitation with motor<\/li>\n<li>harmonics<\/li>\n<\/ul>\n<p><strong>Internal faults<\/strong> can occur in a capacitor. Protective devices shall be used to isolate promptly the faulty capacitor before the unit case rupture. Properly rated, High Rated Current (HRC) <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LXN1YmNhdGVnb3J5Lzg3OTAyLW1lZGl1bS12b2x0YWdlLWZ1c2Vz&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">fuses<\/a> is the most cost-effective solution for the protection of delta connected capacitor units used for individual compensation of motors. It is important to mention that fuses for motors are not suitable to protect capacitors. They are overrated to withstand motor starting current, and too slow to operate with capacitors.<\/p>\n<p> <img loading=\"lazy\" decoding=\"async\" class=\"alignleft wp-image-43647\" src=\"https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Inrush-499x1024.png\" alt=\"capacitor connection higher voltage graph\" width=\"122\" height=\"250\" srcset=\"https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Inrush-499x1024.png 499w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Inrush-146x300.png 146w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Inrush-768x1576.png 768w\" sizes=\"auto, (max-width: 122px) 100vw, 122px\" \/> <\/p>\n<p>&nbsp;<\/p>\n<p><strong>Inrush current<\/strong> occurs when capacitor units are switched on. This inrush current can be significantly increased if other capacitors connected in parallel are already energized (back-to-back switching). In this case, inrush reactors are required to reduce the transient overcurrent to values acceptable for the capacitor (100 In) and the switching device.<\/p>\n<p>Typical values for inrush reactors range from 50 to 400 \u00b5H.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Auto-excitation<\/strong> can occur when capacitor and motor remain permanently connected after disconnection. In this case, the motor could behave as a generator by self-excitation during the deceleration and may cause over-voltages large enough to produce capacitor failures. To prevent this phenomenon, the capacitor current must be lower than the no-load magnetizing current of the motor. A value of 90% of no-load current is recommended.<\/p>\n<p> <img loading=\"lazy\" decoding=\"async\" class=\"alignright wp-image-43650 size-thumbnail\" src=\"https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Autoexcitation-150x150.png\" alt=\"Autoexcitation\" width=\"150\" height=\"150\" srcset=\"https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Autoexcitation-150x150.png 150w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Autoexcitation-300x300.png 300w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Autoexcitation-768x768.png 768w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Autoexcitation-1024x1024.png 1024w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Autoexcitation-125x125.png 125w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Autoexcitation.png 1278w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/> <\/p>\n<p>A motor\u2019s no-load-current is typically in the range 30 to 40% of its rated value. From a practical point of view, auto-excitation is most likely to occur when the motor power factor is relatively low, under 0.8, and installation power factor objective is high, above 0.95.<\/p>\n<p> <img loading=\"lazy\" decoding=\"async\" class=\"alignleft wp-image-43649 size-thumbnail\" src=\"https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Harmonics-150x150.png\" alt=\"harmonics \" width=\"150\" height=\"150\" srcset=\"https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Harmonics-150x150.png 150w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Harmonics-300x300.png 300w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Harmonics-768x768.png 768w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Harmonics-1024x1024.png 1024w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Harmonics-125x125.png 125w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Harmonics.png 1278w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/> <\/p>\n<p><strong>Harmonics<\/strong> are high order currents leading to excessive heating of the capacitor. They have to be considered for permanent operation. Typical solution are detuned reactors.<\/p>\n<p>In some cases, motor starters may produce harmonics during the start-up. Given the short duration, no specific protection will be necessary.<\/p>\n<h2><strong>Summary of recommended solutions\u00a0<\/strong><strong>for capacitor bank protection in motor applications with\u00a0individual power factor correction<\/strong><\/h2>\n<p>On the figure below is shown a typical arrangement for individual compensation of motor.<\/p>\n<p> <img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-medium wp-image-43653\" src=\"https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Starting-SLD-300x189.png\" alt=\"individual compensation of motor\" width=\"300\" height=\"189\" srcset=\"https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Starting-SLD-300x189.png 300w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Starting-SLD-768x484.png 768w, https:\/\/blog.schneider-electric.com\/wp-content\/uploads\/2017\/12\/Starting-SLD-1024x645.png 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/> <\/p>\n<p><strong>Motor fuses<\/strong> (or other protection) are rated to withstand starting, 3-7 time the motor rated current. These <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LXN1YmNhdGVnb3J5Lzg3OTAyLW1lZGl1bS12b2x0YWdlLWZ1c2Vz&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">fuses<\/a> will not protect the capacitor unit.<\/p>\n<ol>\n<li><strong>Capacitor HRC fuses<\/strong> are specific to protect capacitor in case of an internal fault. When determining <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LXN1YmNhdGVnb3J5Lzg3OTAyLW1lZGl1bS12b2x0YWdlLWZ1c2Vz&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">fuse<\/a> rating, inrush currents and capacitor case rupture curves must be taken into consideration. The rating should be at least 1.7 the capacitor rated current<\/li>\n<li><strong>Inrush reactors<\/strong> are necessary in case of back-to-back capacitor configuration, to limit inrush current. It is the case with several motors with individual PFC or with <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LWNhdGVnb3J5LzQzMDAtcG93ZXItcXVhbGl0eS1hbmQtcG93ZXItZmFjdG9yLWNvcnJlY3Rpb24%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">capacitor bank<\/a> on the same busbar. Single motor with no other capacitor bank in parallel can go without inrush reactors but usually, go with in case of the later additional motor.<\/li>\n<li><strong>Correct-Sizing<\/strong> of capacitors is essential to avoid auto-excitation phenomenon when motor and capacitor remain connected after disconnection from the supply.<\/li>\n<\/ol>\n<p>It is recommended to verify that capacitor current remains below 90% of the motor no-load current. Conservative recommendation is to limit capacitor power below 30% of motor power.Otherwise, a dedicated <a href=\"https:\/\/blog.schneider-electric.com\/?feed-stats-url=aHR0cHM6Ly93d3cuc2NobmVpZGVyLWVsZWN0cmljLmNvbS9lbi9wcm9kdWN0LWNhdGVnb3J5Lzg4MDI1LXN3aXRjaGdlYXItY29tcG9uZW50cw%3D%3D&#038;feed-stats-url-post-id=43644\" target=\"_blank\" rel=\"noopener\">contactor<\/a> to disconnect the capacitor from the motor before the supply disconnection has to be added. But additional cost and place need to be evaluated.<\/p>\n<p>  <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/blog.schneider-electric.com\/?feed-stats-post-id=43644\" width=\"1\" height=\"1\" style=\"display: none;\" \/><\/p>\n<p>The post <a rel=\"nofollow\" href=\"https:\/\/blog.schneider-electric.com\/power-management-metering-monitoring-power-quality\/2017\/12\/06\/3-safety-measures-motors-individual-power-factor-correction\/\">3 safety measures for motors with individual power factor correction<\/a> appeared first on <a rel=\"nofollow\" href=\"https:\/\/blog.schneider-electric.com\">Schneider Electric Blog<\/a>.<\/p>\n<p><a href=\"https:\/\/blog.schneider-electric.com\/power-management-metering-monitoring-power-quality\/2017\/12\/06\/3-safety-measures-motors-individual-power-factor-correction\/\" target=\"bwo\" >http:\/\/blog.schneider-electric.com\/feed\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p><strong>Credit to Author: Jerome Guillet| Date: Wed, 06 Dec 2017 20:51:18 +0000<\/strong><\/p>\n<p>In the continuity of the previous article on 5 Steps for Efficient Motor Management Design, we tackle power quality domain and raise awareness on a particular case of motors with&#8230;  <a href=\"https:\/\/blog.schneider-electric.com\/power-management-metering-monitoring-power-quality\/2017\/12\/06\/3-safety-measures-motors-individual-power-factor-correction\/\" title=\"Read3 safety measures for motors with individual power factor correction\">Read more &#187;<\/a><\/p>\n<p>The post <a rel=\"nofollow\" href=\"https:\/\/blog.schneider-electric.com\/power-management-metering-monitoring-power-quality\/2017\/12\/06\/3-safety-measures-motors-individual-power-factor-correction\/\">3 safety measures for motors with individual power factor correction<\/a> appeared first on <a rel=\"nofollow\" href=\"https:\/\/blog.schneider-electric.com\">Schneider Electric Blog<\/a>.<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"colormag_page_container_layout":"default_layout","colormag_page_sidebar_layout":"default_layout","footnotes":""},"categories":[12389,12388],"tags":[15373,16868,16869,16870,12446,13150,13019,13051,13052],"class_list":["post-10740","post","type-post","status-publish","format-standard","hentry","category-scadaics","category-schneider","tag-capacitor-banks","tag-motors","tag-power-factor","tag-power-factor-correction","tag-power-management","tag-power-quality","tag-switchgear","tag-variable-speed-drives","tag-vsd"],"_links":{"self":[{"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/posts\/10740","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/comments?post=10740"}],"version-history":[{"count":0,"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/posts\/10740\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/media?parent=10740"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/categories?post=10740"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.palada.net\/index.php\/wp-json\/wp\/v2\/tags?post=10740"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}