{"id":64482,"date":"2025-05-12T09:47:01","date_gmt":"2025-05-12T06:47:01","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=64482"},"modified":"2026-09-30T18:34:36","modified_gmt":"2026-09-30T15:34:36","slug":"single-phase-transformer","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/engineering\/single-phase-transformer\/","title":{"rendered":"Single Phase Transformer Calculator"},"content":{"rendered":"<section class=\"not-prose calculator-box\" aria-labelledby=\"calculator-title\"><div class=\"flex items-baseline sm:items-center justify-between gap-2 sm:gap-3\"><div class=\"flex flex-col sm:flex-row sm:items-center gap-2\"><span class=\"icon icon-calculator text-primary-700! text-base! dark:text-primary-300!\" aria-hidden=\"true\"><\/span><h2 id=\"calculator-title\" class=\"text-lg font-display font-bold\">Single-Phase Transformer Voltage &amp; Current Estimator<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"64482\" data-favorite-title=\"Single Phase Transformer\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/engineering\/single-phase-transformer\/\" data-favorite-excerpt=\"Calculate secondary voltage, secondary current, and turns ratio for a single-phase transformer. Enter primary voltage, primary and secondary turns, and primary current to get instant results.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-magnet\">\n    <span class=\"icon icon-shape-star-empty\" aria-hidden=\"true\"><\/span>\n  <\/button>\n  <div class=\"calcdash-favorite__tip\" aria-hidden=\"true\">\n   <span class=\"favorite-tooltip\" id=\"favorite-tooltip\"><\/span>\n  <\/div>\n  <span class=\"sr-only\" role=\"status\" id=\"favorite-status\"><\/span>\n<\/div><\/div><form action=\"https:\/\/wpcalc.com\/en\/engineering\/single-phase-transformer\/\" method=\"POST\" class=\"calculator\" id=\"calculator-64482\" data-post=\"64482\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Primary Voltage<\/label><div class=\"term\">V\u209a<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"primary_voltage\" id=\"field-1\" aria-describedby=\"calc-unit-1 calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"1\" value=\"220\"\/><div class=\"unit\" id=\"calc-unit-1\">V<\/div><small id=\"calc-info-1\">Voltage applied to the primary coil<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">Primary Turns<\/label><div class=\"term\">N\u209a<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"primary_turns\" id=\"field-2\" aria-describedby=\"calc-info-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"1\" value=\"500\"\/><small id=\"calc-info-2\">Number of turns in primary coil<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-3\">Secondary Turns<\/label><div class=\"term\">N\u209b<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"secondary_turns\" id=\"field-3\" aria-describedby=\"calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"1\" value=\"100\"\/><small id=\"calc-info-3\">Number of turns in secondary coil<\/small><\/div><div class=\"field has-term\" id=\"input-4\"><label for=\"field-4\">Primary Current<\/label><div class=\"term\">I\u209a<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"primary_current\" id=\"field-4\" aria-describedby=\"calc-unit-4 calc-info-4\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0.01\" value=\"1\"\/><div class=\"unit\" id=\"calc-unit-4\">A<\/div><small id=\"calc-info-4\">Current flowing into the primary winding<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"64482\">Calculate<\/button><button type=\"reset\">Reset<\/button><\/div><div class=\"field is-checkbox hidden!\" id=\"field-auto-calc\"><input type=\"checkbox\" id=\"auto-calc\"><label for=\"auto-calc\">Calculate automatically<\/label><small>If enabled, the result will update automatically when you change any value.<\/small><\/div><div class=\"fieldset-result is-hidden\" aria-labelledby=\"result-title\" aria-live=\"polite\" role=\"region\"> <h3 class=\"result-title bg-gradient-to-r from-primary-50 to-gray-50 dark:from-primary-900 dark:to-gray-800\" id=\"result-title\"><span class=\"icon icon-s-pulse\" aria-hidden=\"true\"><\/span> Your Results<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Secondary Voltage (Vs)<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"V\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-2\"><span class=\"field-title\"><span>Secondary Current (Is)<\/span><\/span><span class=\"field-value\" id=\"result-2\" data-unit=\"A\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-3\"><span class=\"field-title\"><span>Turns Ratio (Np:Ns)<\/span><\/span><span class=\"field-value\" id=\"result-3\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><\/div><div class=\"result-actions\"><button type=\"button\" class=\"copy-link\"><svg viewBox=\"0 0 20 20\" fill=\"currentColor\" aria-hidden=\"true\"><path d=\"M12.232 4.232a2.5 2.5 0 0 1 3.536 3.536l-1.225 1.224a.75.75 0 0 0 1.061 1.06l1.224-1.224a4 4 0 0 0-5.656-5.656l-3 3a4 4 0 0 0 .225 5.865.75.75 0 0 0 .977-1.138 2.5 2.5 0 0 1-.142-3.667l3-3Z\"\/><path d=\"M11.603 7.963a.75.75 0 0 0-.977 1.138 2.5 2.5 0 0 1 .142 3.667l-3 3a2.5 2.5 0 0 1-3.536-3.536l1.225-1.224a.75.75 0 0 0-1.061-1.06l-1.224 1.224a4 4 0 1 0 5.656 5.656l3-3a4 4 0 0 0-.225-5.865Z\"\/><\/svg><span class=\"copy-link__text\">Copy link to this calculation<\/span><\/button><span class=\"sr-only\" role=\"status\" id=\"copy-link-status\"><\/span><\/div><\/div><a href=\"#respond\" class=\"hidden transition-opacity duration-300 opacity-0 w-50 text-sm justify-center items-center gap-2 px-4 py-2 rounded bg-gray-200 text-gray-700 hover:bg-gray-300\" id=\"leave-comment\"><span class=\"icon icon-comments\" aria-hidden=\"true\"><\/span>Leave a Comment<\/a><\/form><\/section><section id=\"calc-reactions\" class=\"not-prose hidden my-12 bg-gradient-to-r from-primary-50 to-gray-50 border border-indigo-100 rounded-xl px-6 py-4 shadow-sm\" data-post=\"64482\" aria-live=\"polite\" aria-labelledby=\"calc-reactions-title\"><p id=\"calc-reactions-title\" class=\"text-sm text-gray-500 text-center mb-2\">How did this result make you feel?<\/p><div role=\"group\" aria-labelledby=\"calc-reactions-title\" class=\"grid grid-cols-3 sm:flex sm:flex-row sm:justify-around gap-4 sm:items-center sm:flex-wrap\"><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"like\"><span class=\"reaction-count\" data-reaction-count=\"like\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude00 <\/span><span class=\"reaction-description font-medium\">Like <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"helpful\"><span class=\"reaction-count\" data-reaction-count=\"helpful\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\udca1 <\/span><span class=\"reaction-description font-medium\">Helpful <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"confused\"><span class=\"reaction-count\" data-reaction-count=\"confused\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude15 <\/span><span class=\"reaction-description font-medium\">Confused <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"disappointed\"><span class=\"reaction-count\" data-reaction-count=\"disappointed\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude1e <\/span><span class=\"reaction-description font-medium\">Disappointed <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"inaccurate\"><span class=\"reaction-count\" data-reaction-count=\"inaccurate\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\u274c <\/span><span class=\"reaction-description font-medium\">Inaccurate <\/span><\/button><\/div><div id=\"reaction-message\" class=\"hidden mt-8 rounded-md border border-primary-100 bg-white\/50 backdrop-blur-sm px-4 py-2 text-sm text-center shadow-sm\"><\/div><\/section><div class=\"calcdash-ad not-prose calcdash-ad--calc_result calcdash-ad--in-article\"><ins class=\"adsbygoogle\" style=\"display:block\" data-ad-client=\"ca-pub-1721569815777345\" data-ad-slot=\"6317458308\" data-ad-layout=\"in-article\" data-ad-format=\"fluid\"><\/ins><script>(adsbygoogle = window.adsbygoogle || []).push({});<\/script><\/div>\n<style id=\"wpcoderpro-inline-1\">.formula-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section class=\"formula-box\" aria-labelledby=\"formula-title\">\r\n\t<div id=\"formula-title\" class=\"not-prose font-display mb-4\"><span class=\"icon icon-formula\" aria-hidden=\"true\"><\/span><h2>Single Phase Transformer Formula<\/h2><\/div>\r\n\t<figure class=\"not-prose formula\">\r\n\t\t<figcaption class=\"formula-title\">Formula<\/figcaption>\r\n\t\t<div class=\"text-base text-gray-800\" id=\"formula\">\n\\[ V_s = \\frac{V_p \\cdot N_s}{N_p} \\]\n\\[ I_s = \\frac{I_p \\cdot N_p}{N_s} \\]\n\\[ \\text{Turns ratio} = \\frac{N_p}{N_s} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(V_p\\) \u2014 primary voltage, applied to the primary winding (V)<\/li>\n<li>\\(V_s\\) \u2014 secondary voltage, induced in the secondary winding (V)<\/li>\n<li>\\(N_p\\) \u2014 number of turns in the primary winding<\/li>\n<li>\\(N_s\\) \u2014 number of turns in the secondary winding<\/li>\n<li>\\(I_p\\) \u2014 primary current (A)<\/li>\n<li>\\(I_s\\) \u2014 secondary current (A)<\/li>\n<\/ul>\n<p>These equations describe an ideal single-phase transformer: voltage scales in proportion to the turns ratio, while current scales in the inverse proportion, so that the apparent power on both sides stays equal.<\/p>\n<p>\r\n<\/section>\n<style id=\"wpcoderpro-inline-459\">.calculation-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section id=\"calculation\" class=\"calculation-box\" aria-labelledby=\"calculation-title\">\r\n\t<div id=\"calculation-title\" class=\"not-prose font-display\"><span class=\"icon icon-unordered-list\" aria-hidden=\"true\"><\/span><h2>Single Phase Transformer \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> a step-down transformer has a primary winding of 500 turns connected to a 220 V supply, a secondary winding of 100 turns, and a primary current of 1 A.<\/p>\n<p>\\[ V_s = \\frac{V_p \\cdot N_s}{N_p} = \\frac{220 \\cdot 100}{500} = 44~\\text{V} \\]<\/p>\n<p>\\[ I_s = \\frac{I_p \\cdot N_p}{N_s} = \\frac{1 \\cdot 500}{100} = 5~\\text{A} \\]<\/p>\n<p>\\[ \\text{Turns ratio} = N_p : N_s = 500:100 = 5:1 \\]<\/p>\n<p><strong>Result:<\/strong> the secondary voltage is 44 V, the secondary current is 5 A, and the turns ratio is 500:100 (5:1). The transformer steps 220 V down to 44 V and, correspondingly, steps the 1 A primary current up to 5 A on the secondary side.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Enter the <strong>Primary Voltage<\/strong> (\\(V_p\\)) in volts \u2014 the voltage applied to the primary winding, e.g. 220 V.<\/li>\n<li>Enter the <strong>Primary Turns<\/strong> (\\(N_p\\)) \u2014 the number of turns in the primary winding.<\/li>\n<li>Enter the <strong>Secondary Turns<\/strong> (\\(N_s\\)) \u2014 the number of turns in the secondary winding.<\/li>\n<li>Enter the <strong>Primary Current<\/strong> (\\(I_p\\)) in amperes \u2014 the current flowing into the primary winding.<\/li>\n<li>Read the results: the <strong>Secondary Voltage (Vs)<\/strong> in volts, the <strong>Secondary Current (Is)<\/strong> in amperes, and the <strong>Turns Ratio (Np:Ns)<\/strong>.<\/li>\n<\/ol>\n<p>All input values must be greater than zero. If you are designing a transformer rather than analyzing an existing one, you can enter any convenient trial value for the current \u2014 the voltage and turns results depend only on the voltage and the two turn counts.<\/p>\n<h2>What Is a Single-Phase Transformer?<\/h2>\n<p>A single-phase transformer is a static device that transfers electrical energy between two circuits through electromagnetic induction. It consists of two windings \u2014 primary and secondary \u2014 wound on a shared magnetic core. Alternating current in the primary winding creates a changing magnetic flux in the core, which induces a voltage in the secondary winding. Because there is no electrical connection between the windings, a transformer also provides galvanic isolation.<\/p>\n<p>The key relationship in any transformer is the turns ratio \\(N_p\/N_s\\). If the secondary has fewer turns than the primary, the transformer steps the voltage down; if it has more turns, the voltage steps up. Current behaves in the opposite way: a step-down transformer with a ratio of 5:1 reduces the voltage fivefold but increases the available secondary current fivefold. This is why transformers are described as converting between voltage and current while keeping the apparent power roughly constant: \\(V_p \\cdot I_p \\approx V_s \\cdot I_s\\).<\/p>\n<p>Single-phase transformers are found everywhere in residential and light commercial power systems \u2014 doorbell transformers, welding supplies, HVAC control circuits, battery chargers, and the distribution transformers that drop the utility voltage from several kilovolts to the 230 V or 120 V used in homes. Engineers and electricians use the turns ratio calculations shown above to select a transformer for a load, to verify winding data when repairing a unit, or to check whether an existing transformer is suitable for a new application. For a deeper look at the power side of the analysis, see the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/real-reactive-power\/\">Real and Reactive Power calculator<\/a>.<\/p>\n<h2>Interpreting the Results<\/h2>\n<p>The <strong>secondary voltage<\/strong> tells you the no-load output voltage of the transformer. Under load, the actual output voltage will be slightly lower due to winding resistance and leakage reactance \u2014 typically by 2\u20136% for small units.<\/p>\n<p>The <strong>secondary current<\/strong> is the current the transformer can deliver on the secondary side for the given primary current. It also tells you the current ratio: since power is conserved, a transformer that steps voltage down must step current up by the same factor.<\/p>\n<p>The <strong>turns ratio<\/strong> \\(N_p:N_s\\) is usually simplified to its lowest whole numbers (e.g. 500:100 becomes 5:1). A ratio greater than 1 means the transformer steps voltage down; less than 1 means it steps voltage up. The actual winding numbers matter in practice, because fewer total turns for the same ratio mean a smaller, cheaper core but higher magnetizing current.<\/p>\n<h2>Assumptions and Limitations<\/h2>\n<ul>\n<li><strong>Ideal transformer model:<\/strong> the calculations assume 100% coupling between windings and no losses. Real transformers have copper losses (winding resistance), core losses (hysteresis and eddy currents), and leakage flux, so measured values will differ from calculated ones by a few percent.<\/li>\n<li><strong>Unity power factor:<\/strong> the current relationship assumes the load draws real power efficiently. With reactive loads, currents on both sides can be higher than the real-power transfer would suggest.<\/li>\n<li><strong>Frequency and core saturation:<\/strong> the model does not check whether the core will saturate. A transformer designed for 60 Hz will draw excessive magnetizing current if run at 50 Hz at the same voltage, and vice versa.<\/li>\n<li><strong>Rating check:<\/strong> this tool does not verify that the transformer can handle the resulting power. Always confirm that \\(V_s \\cdot I_s\\) stays within the transformer's VA rating, and size the connecting wires appropriately with the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/wire-gauge\/\">Wire Gauge calculator<\/a>.<\/li>\n<li><strong>Single-phase only:<\/strong> the formulas apply to single-phase units. Three-phase transformers require a factor of \\(\\sqrt{3}\\) in the power equations and per-phase analysis.<\/li>\n<\/ul>\n<p>If you are also designing or analyzing the windings themselves, the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/coil-physical-properties\/\">Physical Properties of Coil calculator<\/a> can help you estimate inductance and wire length for each winding.<\/p>\n<h2>Quick Reference: Turns Ratio Examples<\/h2>\n<table>\n<thead>\n<tr>\n<th>Turns ratio (Np:Ns)<\/th>\n<th>Primary voltage<\/th>\n<th>Secondary voltage<\/th>\n<th>Current relationship<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>10:1<\/td>\n<td>230 V<\/td>\n<td>23 V<\/td>\n<td>\\(I_s = 10 \\cdot I_p\\)<\/td>\n<\/tr>\n<tr>\n<td>5:1<\/td>\n<td>220 V<\/td>\n<td>44 V<\/td>\n<td>\\(I_s = 5 \\cdot I_p\\)<\/td>\n<\/tr>\n<tr>\n<td>1:1<\/td>\n<td>230 V<\/td>\n<td>230 V<\/td>\n<td>\\(I_s = I_p\\) (isolation transformer)<\/td>\n<\/tr>\n<tr>\n<td>1:2<\/td>\n<td>110 V<\/td>\n<td>220 V<\/td>\n<td>\\(I_s = 0.5 \\cdot I_p\\)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>A 1:1 transformer changes neither voltage nor current \u2014 it is used purely for isolation between circuits.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calculate secondary voltage, secondary current, and turns ratio for a single-phase transformer. Enter primary voltage, primary and secondary turns, and primary current to get instant results.<\/p>\n","protected":false},"author":70,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4],"tags":[93],"class_list":["post-64482","post","type-post","status-publish","format-standard","hentry","category-engineering","tag-coils-transformers"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/64482","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/users\/70"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/comments?post=64482"}],"version-history":[{"count":3,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/64482\/revisions"}],"predecessor-version":[{"id":66012,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/64482\/revisions\/66012"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=64482"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=64482"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=64482"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}