{"id":6182,"date":"2018-04-06T07:23:20","date_gmt":"2018-04-06T06:23:20","guid":{"rendered":"https:\/\/engineernewsnetwork.com\/blog\/?p=6182"},"modified":"2018-04-03T12:30:36","modified_gmt":"2018-04-03T11:30:36","slug":"why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing","status":"publish","type":"post","link":"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/","title":{"rendered":"Why AC DC variable voltage sources are still necessary for testing"},"content":{"rendered":"<p><strong>Producing robust variable voltage output power for electronic applications has not always been easy.\u00a0Here, Steve Hughes\u00a0explains why AC DC variable voltage sources are still essential in testing applications<\/strong><\/p>\n<p>Historically, variable transformers were the most efficient way to produce output power for a given application. They would achieve this by using a brushed gear that would move over the windings, adjusting the output voltage to any level required.<br \/>\n<script async src=\"\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js\"><\/script><br \/>\n<ins class=\"adsbygoogle\" style=\"display: block; text-align: center;\" data-ad-layout=\"in-article\" data-ad-format=\"fluid\" data-ad-client=\"ca-pub-7565662001938327\" data-ad-slot=\"7585079586\"><\/ins><br \/>\n<script>\n     (adsbygoogle = window.adsbygoogle || []).push({});\n<\/script><br \/>\nUsed in combination with rectifier circuits \u2014 circuits that convert alternating current (AC) to direct current (DC) \u2014 variable transformers provide a variety of benefits such as being able to control the speed of a motor, or providing precise control in electroplating or electrophoretic paint-coating processes.<\/p>\n<p>Even old fashioned impressed current cathodic protection (ICCP) power supplies, which were designed to tackle corrosion in marine applications, used variable transformers.<\/p>\n<figure id=\"attachment_6183\" aria-describedby=\"caption-attachment-6183\" style=\"width: 618px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/engineernewsnetwork.com\/blog\/wp-content\/uploads\/2018\/04\/Image-REOLAB-3000-E.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-6183\" src=\"https:\/\/engineernewsnetwork.com\/blog\/wp-content\/uploads\/2018\/04\/Image-REOLAB-3000-E-683x1024.jpg\" alt=\"Why AC DC variable voltage sources are still necessary for testing\" width=\"618\" height=\"927\" \/><\/a><figcaption id=\"caption-attachment-6183\" class=\"wp-caption-text\">For engineers looking for a robust variable output power supply, it\u2019s easy to overlook variable voltage transformers. However, these should not be taken for granted. Variable voltage transformers offer distinct advantages in testing applications<\/figcaption><\/figure>\n<p>However, as the demand for current and voltages increased, variable voltage sources began to be made from modern electronics. Unfortunately, these can become more expensive and less robust when dealing with high power applications.<\/p>\n<p>Many modern variable power systems require protection circuits to offer trouble-free use and suffer from problems such as harmonic currents and electromagnetic interference (EMI), which can lead to overheating, overload, short circuiting, unnecessarily high power-consumption and shorter equipment lifecycles.<\/p>\n<p>One of the most popular uses of\u00a0variable AC DC voltage supplies is in test applications today, where there is often a need for the test power-supply to be frequently exposed to high inrush currents and short circuits.<\/p>\n<p>Inferior power supplies can necessitate frequent fuse replacements or, even worse, lead to semiconductor failure.<\/p>\n<p>Variable transformers are often used in conjunction with an isolation transformer to form a safe, isolated supply or with a high voltage transformer to provide a high voltage (HV) supply if the application demands it.<\/p>\n<p>They are usually rated from 1A to 32A. However, they can be designed to achieve power ratings up to 1MVA.<\/p>\n<p>Their robustness means that\u00a0variable transformers are perfect for test bench applications.<\/p>\n<p>The typical short-term overload of a variable transformer is 10 times nominal power for 0.5 seconds, a much higher capability than test-power systems that use modern electronics.<\/p>\n<p>Today, <span class=\"highlight highlight-blue\"><a href=\"https:\/\/engineernewsnetwork.com\/blog\/power-quality-industry-is-wasting-potential-44twh-each-year\/\" target=\"_blank\" rel=\"noopener\">REO UK<\/a><\/span> supplies robust test power supplies for cable testing, railway traction, connector testing, as well as any electrical application that requires test power to be smooth, stable and free of EMI.<\/p>\n<p>REO&#8217;s variable transformers also overcome a traditional limitation of this kind of power supply, which was that it had to be physically adjusted using a control wheel.<\/p>\n<p>However, recent developments with servo motors and feedback regulators mean that they can now be controlled automatically.<\/p>\n<p>What&#8217;s more, <span class=\"highlight highlight-blue\"><a href=\"https:\/\/engineernewsnetwork.com\/blog\/industrial-ethernet-gets-boost-from-power-quality-specialist\/\" target=\"_blank\" rel=\"noopener\">REO UK<\/a><\/span> manufactures control electronics that allow them to be regulated using current or voltage feedback that is compatible with fieldbus networks using standards such as ProfiNet or CanBus.<\/p>\n<p>For engineers looking for a robust variable output power supply, it&#8217;s easy to overlook variable voltage transformers. However, these should not be taken for granted, offering distinct advantages in testing applications.<\/p>\n<p>Steve Hughes is, managing director of\u00a0power quality specialist <span class=\"highlight highlight-blue\"><a href=\"http:\/\/www.reo.co.uk\/electrical_testing\" target=\"_blank\" rel=\"noopener\">REO UK<\/a><\/span>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Producing robust variable voltage output power for electronic applications has not always been easy.\u00a0Here, Steve Hughes\u00a0explains why AC DC variable voltage sources are still essential in testing applications Historically, variable transformers were the most efficient way to produce output power for a given application. They would achieve this by using a brushed gear that would &hellip;<\/p>\n","protected":false},"author":1,"featured_media":6183,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[3422,3424,472,3423,59,3421],"class_list":["post-6182","post","type-post","status-publish","format-standard","has-post-thumbnail","","category-process","tag-cable-testing","tag-connector-testing","tag-power-quality","tag-railway-traction","tag-reo-uk","tag-variable-voltage-transformers"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.2 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Why AC DC variable voltage sources are still necessary for testing - Engineer News Network<\/title>\n<meta name=\"description\" content=\"For engineers looking for a robust variable output power supply, it\u2019s easy to overlook variable voltage transformers. However, these should not be taken for granted. Variable voltage transformers offer distinct advantages in testing applications\" \/>\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\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Why AC DC variable voltage sources are still necessary for testing - Engineer News Network\" \/>\n<meta property=\"og:description\" content=\"For engineers looking for a robust variable output power supply, it\u2019s easy to overlook variable voltage transformers. However, these should not be taken for granted. Variable voltage transformers offer distinct advantages in testing applications\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/\" \/>\n<meta property=\"og:site_name\" content=\"Engineer News Network\" \/>\n<meta property=\"article:published_time\" content=\"2018-04-06T06:23:20+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2018\/04\/Image-REOLAB-3000-E-e1522750944102.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"3826\" \/>\n\t<meta property=\"og:image:height\" content=\"2476\" \/>\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=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/\"},\"author\":{\"name\":\"admin\",\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/#\/schema\/person\/4477342aea8e299c6a21761e513ea8e1\"},\"headline\":\"Why AC DC variable voltage sources are still necessary for testing\",\"datePublished\":\"2018-04-06T06:23:20+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/\"},\"wordCount\":568,\"image\":{\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2018\/04\/Image-REOLAB-3000-E-e1522750944102.jpg\",\"keywords\":[\"cable testing\",\"connector testing\",\"power quality\",\"railway traction\",\"REO UK\",\"Variable voltage transformers\"],\"articleSection\":[\"Process\"],\"inLanguage\":\"en-GB\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/\",\"url\":\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/\",\"name\":\"Why AC DC variable voltage sources are still necessary for testing - Engineer News Network\",\"isPartOf\":{\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/why-ac-dc-variable-voltage-sources-are-still-necessary-for-testing\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.engineernewsnetwork.com\/blog\/wp-content\/uploads\/2018\/04\/Image-REOLAB-3000-E-e1522750944102.jpg\",\"datePublished\":\"2018-04-06T06:23:20+00:00\",\"author\":{\"@id\":\"https:\/\/www.engineernewsnetwork.com\/blog\/#\/schema\/person\/4477342aea8e299c6a21761e513ea8e1\"},\"description\":\"For engineers looking for a robust variable output power supply, it\u2019s easy to overlook variable voltage transformers. 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