{"id":100138,"date":"2026-02-15T20:19:46","date_gmt":"2026-02-15T20:19:46","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100138"},"modified":"2026-07-12T15:23:03","modified_gmt":"2026-07-12T15:23:03","slug":"insulation-resistance-calculator","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/vi\/calculators\/insulation-resistance-calculator\/","title":{"rendered":"C\u00f4ng c\u1ee5 phi\u00ean d\u1ecbch \u0111i\u1ec7n tr\u1edf c\u00e1ch \u0111i\u1ec7n \u0111\u1ed9ng c\u01a1 (Megger) | IEEE 43"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Motor Insulation Resistance Interpreter\",\"description\":\"Interpret motor insulation resistance (megger) readings per IEEE 43. 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a:hover{text-decoration:underline}\n.vc-footer-links{margin-top:8px;font-size:12px}\n.vc-footer-links a{margin:0 8px}\n@media print{.vc-section-body{max-height:none!important}.vc-faq-a{max-height:none!important}.vc-results{max-height:none!important;padding:24px!important}.vc-copy-btn,.vc-section-chevron,.vc-faq-chevron,.vc-promo{display:none!important}}\n<\/style>\n\n<div class=\"vc-calculator\" id=\"vc-insulation-resistance\">\n\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool<\/p>\n    <h1 class=\"vc-header-title\">Motor Insulation Resistance Interpreter<\/h1>\n    <p class=\"vc-header-subtitle\">Interpret megger test results per IEEE Std 43. Calculate minimum acceptable insulation resistance, temperature-corrected values, polarization index, and trending recommendations.<\/p>\n    <div class=\"vc-badges\">\n        <span class=\"vc-badge\">IEEE 43<\/span>\n        <span class=\"vc-badge\">Megger Test<\/span>\n        <span class=\"vc-badge\">Polarization Index<\/span>\n    <\/div>\n<\/header>\n\n<div class=\"vc-card\">\n    <form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\">\n        <div class=\"vc-form-grid\">\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-ir1\">1-Minute IR Reading <span class=\"vc-label-hint\">(M\u03a9)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-ir1\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 500\" value=\"500\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-ir10\">10-Minute IR Reading <span class=\"vc-label-hint\">(M\u03a9, optional for PI)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-ir10\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 2000\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-voltage\">Motor Rated Voltage <span class=\"vc-label-hint\">(V)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-voltage\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 4160\" value=\"4160\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-temp\">Test Temperature <span class=\"vc-label-hint\">(\u00b0C)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-temp\" inputmode=\"decimal\" step=\"any\" placeholder=\"e.g. 25\" value=\"25\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-age\">Motor Age \/ Condition<\/label>\n                <select class=\"vc-select\" id=\"vc-age\">\n                    <option value=\"new\">New or recently rewound<\/option>\n                    <option value=\"service\" selected>In service (normal)<\/option>\n                    <option value=\"old\">Aged (>20 years)<\/option>\n                <\/select>\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-insclass\">Insulation Class<\/label>\n                <select class=\"vc-select\" id=\"vc-insclass\">\n                    <option value=\"thermoplastic\">Thermoplastic (older)<\/option>\n                    <option value=\"thermoset\" selected>Thermoset (modern, epoxy)<\/option>\n                <\/select>\n            <\/div>\n        <\/div>\n    <\/form>\n\n    <div class=\"vc-results vc-visible\" id=\"vc-results\">\n        <div class=\"vc-results-head\">\n            <h2 class=\"vc-results-title\">Interpretation<\/h2>\n            <button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\">\n                <svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg>\n                Copy\n            <\/button>\n        <\/div>\n        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\">\n                <div class=\"vc-rcard-label\">Overall Assessment<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-verdict\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Minimum Acceptable (IEEE 43)<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-minimum\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Corrected IR @ 40\u00b0C<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-corrected\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Temperature Correction Factor<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-tempfactor\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Polarization Index (PI)<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-pi\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Recommended Test Voltage<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-testvolt\">\u2014<\/div>\n            <\/div>\n        <\/div>\n        <div class=\"vc-rcard\" style=\"margin-bottom:12px;\">\n            <div class=\"vc-rcard-label\">Trending Recommendation<\/div>\n            <div id=\"vc-r-trending\" style=\"font-size:14px;color:var(--vc-ink-secondary);margin-top:6px;\">\u2014<\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Theory -->\n<div class=\"vc-section vc-open\" id=\"vc-sec-theory\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udcd8<\/span>\n            <span class=\"vc-section-title\">Theory &#038; Standards<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner vc-theory\">\n            <h3>Minimum Insulation Resistance (IEEE 43)<\/h3>\n            <p>Per IEEE Std 43, the minimum recommended 1-minute insulation resistance at 40 \u00b0C is:<\/p>\n            <div class=\"vc-formula-box\">R_min = kV + 1 &nbsp;&nbsp;(M\u03a9)<\/div>\n            <p>Where <strong>kV<\/strong> is the rated voltage in kilovolts. For a 4160V motor: R_min = 4.16 + 1 = 5.16 M\u03a9.<\/p>\n            <p><strong>\u26a0\ufe0f Scope of the kV + 1 rule:<\/strong> IEEE Std 43 recommends kV + 1 M\u03a9 for windings made before about 1970. For most form-wound windings made after about 1970 the recommended minimum is <strong>100 M\u03a9<\/strong>, and for random-wound stators rated below 1 kV it is <strong>5 M\u03a9<\/strong>. For modern form-wound machines, judge the corrected IR against 100 M\u03a9 rather than the kV + 1 value used below.<\/p>\n            <p style=\"font-size:13px;color:var(--vc-ink-muted);\">Reference note: IEEE Std 43-2013 is Inactive-Reserved (since 2024); revision project P43 is in progress.<\/p>\n\n            <h3>Temperature Correction<\/h3>\n            <p>Insulation resistance approximately doubles for every 10 \u00b0C decrease in temperature. To normalize to 40 \u00b0C:<\/p>\n            <div class=\"vc-formula-box\">R\u2084\u2080 = R_T \u00d7 C_T, where C_T = 0.5^((40 \u2212 T)\/10)<\/div>\n            <p>For a reading at 25 \u00b0C: C_T = 0.5^((40\u221225)\/10) = 0.5^1.5 = 0.354. So a 500 M\u03a9 reading at 25 \u00b0C becomes 177 M\u03a9 at 40 \u00b0C.<\/p>\n\n            <h3>Polarization Index (PI)<\/h3>\n            <div class=\"vc-formula-box\">PI = IR\u2081\u2080min \/ IR\u2081min<\/div>\n            <table class=\"vc-table\">\n                <thead><tr><th>PI Value<\/th><th>Insulation Condition<\/th><\/tr><\/thead>\n                <tbody>\n                    <tr><td>&lt; 1.0<\/td><td>Dangerous \u2014 do not energize<\/td><\/tr>\n                    <tr><td>1.0 \u2013 2.0<\/td><td>Questionable<\/td><\/tr>\n                    <tr><td>2.0 \u2013 4.0<\/td><td>Good<\/td><\/tr>\n                    <tr><td>&gt; 4.0<\/td><td>Excellent<\/td><\/tr>\n                <\/tbody>\n            <\/table>\n\n            <h3>Recommended Test Voltages (IEEE 43)<\/h3>\n            <table class=\"vc-table\">\n                <thead><tr><th>Motor Rated Voltage<\/th><th>DC Test Voltage<\/th><\/tr><\/thead>\n                <tbody>\n                    <tr><td>&lt; 1000 V<\/td><td>500 V DC<\/td><\/tr>\n                    <tr><td>1000 \u2013 2500 V<\/td><td>500 \u2013 1000 V DC<\/td><\/tr>\n                    <tr><td>2501 \u2013 5000 V<\/td><td>1000 \u2013 2500 V DC<\/td><\/tr>\n                    <tr><td>5001 \u2013 12000 V<\/td><td>2500 \u2013 5000 V DC<\/td><\/tr>\n                    <tr><td>&gt; 12000 V<\/td><td>5000 \u2013 10000 V DC<\/td><\/tr>\n                <\/tbody>\n            <\/table>\n\n            <div class=\"vc-warning-box\">\n                <p style=\"margin:0;font-size:14px;color:var(--vc-ink-secondary);\"><strong>\u26a0\ufe0f Important:<\/strong> A single IR reading is less meaningful than a trend. Always compare with previous readings taken under similar conditions. A sudden drop (>50%) is more alarming than an absolutely low but stable value.<\/p>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Related -->\n<div class=\"vc-section\" id=\"vc-sec-related\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udd17<\/span>\n            <span class=\"vc-section-title\">Related Calculators<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-related\">\n                <a class=\"vc-related-link\" href=\"\/calculators\/motor-winding-resistance\/\">Winding Resistance Calculator<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/diagnostic-matrix\/\">Vibration Diagnostic Matrix<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/vibration-glossary\/\">Vibration Glossary<\/a>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- FAQ -->\n<div class=\"vc-section\" id=\"vc-sec-faq\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\u2753<\/span>\n            <span class=\"vc-section-title\">Frequently Asked Questions<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<div class=\"vc-promo\">\n    <div class=\"vc-promo-text\">\n        <strong>Vibromera \u2014 Portable Balancing &#038; Vibration Analysis<\/strong><br>\n        Professional field balancing instruments and software. Used in 50+ countries.\n    <\/div>\n    <a class=\"vc-promo-link\" href=\"https:\/\/vibromera.eu\/\" target=\"_blank\" rel=\"noopener\">Learn More<\/a>\n<\/div>\n\n<footer class=\"vc-footer\">\n    <p>\u00a9 2024\u20132025 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a> \u2014 Engineering Calculators<\/p>\n    <p style=\"font-size:12px;margin-top:4px;\">Based on IEEE Std 43. Last updated: February 2025<\/p>\n    <div class=\"vc-footer-links\">\n        <a href=\"\/calculators\/engineering-calculators\/\">All Calculators<\/a>\n        <a href=\"https:\/\/vibromera.eu\/contacts\/\">Contact<\/a>\n    <\/div>\n<\/footer>\n\n<\/div>\n\n<script>\n(function() {\n    'use strict';\n\n    function $(id) { return document.getElementById(id); }\n    function fmt(n, d) {\n        if (isNaN(n) || !isFinite(n)) return '\u2014';\n        var f = n.toFixed(d === undefined ? 2 : d);\n        return f.replace(\/(\\.\\d*?)0+$\/, '$1').replace(\/\\.$\/, '');\n    }\n\n    function getTestVoltage(ratedV) {\n        if (ratedV < 1000) return '500 V DC';\n        if (ratedV <= 2500) return '500\u20131000 V DC';\n        if (ratedV <= 5000) return '1000\u20132500 V DC';\n        if (ratedV <= 12000) return '2500\u20135000 V DC';\n        return '5000\u201310000 V DC';\n    }\n\n    function calculate() {\n        var ir1 = parseFloat($('vc-ir1').value);\n        var ir10 = parseFloat($('vc-ir10').value);\n        var voltage = parseFloat($('vc-voltage').value);\n        var temp = parseFloat($('vc-temp').value);\n        var age = $('vc-age').value;\n        var insclass = $('vc-insclass').value;\n\n        if (isNaN(ir1) || ir1 < 0 || isNaN(voltage) || voltage <= 0) {\n            $('vc-r-verdict').innerHTML = '\u2014';\n            return;\n        }\n\n        var kv = voltage \/ 1000;\n        var rMin = kv + 1; \/\/ M\u03a9 per IEEE 43\n\n        \/\/ Temperature correction to 40\u00b0C\n        var tempC = isNaN(temp) ? 40 : temp;\n        var corrFactor = Math.pow(0.5, (40 - tempC) \/ 10);\n        var ir40 = ir1 * corrFactor;\n\n        \/\/ PI calculation\n        var piVal = NaN;\n        var piText = 'Enter 10-min reading to calculate';\n        var piClass = '';\n        if (!isNaN(ir10) && ir10 > 0 && ir1 > 0) {\n            piVal = ir10 \/ ir1;\n            if (piVal < 1.0) { piText = fmt(piVal, 2) + ' \u2014 <span class=\"vc-status-fail\">DANGEROUS<\/span>'; }\n            else if (piVal < 2.0) { piText = fmt(piVal, 2) + ' \u2014 <span class=\"vc-status-warn\">Questionable<\/span>'; }\n            else if (piVal < 4.0) { piText = fmt(piVal, 2) + ' \u2014 <span class=\"vc-status-pass\">Good<\/span>'; }\n            else { piText = fmt(piVal, 2) + ' \u2014 <span class=\"vc-status-pass\">Excellent<\/span>'; }\n        }\n\n        \/\/ Thermoset PI note\n        if (insclass === 'thermoset' && !isNaN(piVal) && piVal > 5) {\n            piText += '<br><span style=\"font-size:12px;color:var(--vc-ink-muted);\">Note: Thermoset insulation may show very high PI (>5) \u2014 this is normal.<\/span>';\n        }\n\n        \/\/ Overall verdict\n        var verdict, verdictClass;\n        if (ir40 < rMin) {\n            verdict = 'FAIL';\n            verdictClass = 'vc-status-fail';\n        } else if (ir40 < rMin * 5) {\n            verdict = 'MARGINAL \u2014 Monitor closely';\n            verdictClass = 'vc-status-warn';\n        } else if (ir40 < 100) {\n            verdict = 'ACCEPTABLE';\n            verdictClass = 'vc-status-warn';\n        } else {\n            verdict = 'PASS \u2014 Good insulation';\n            verdictClass = 'vc-status-pass';\n        }\n\n        if (!isNaN(piVal) && piVal < 1.0) {\n            verdict = 'FAIL \u2014 PI < 1.0, moisture or contamination likely';\n            verdictClass = 'vc-status-fail';\n        }\n\n        $('vc-r-verdict').innerHTML = '<span class=\"' + verdictClass + '\">' + verdict + '<\/span>';\n        $('vc-r-minimum').innerHTML = fmt(rMin, 1) + ' <span class=\"vc-rcard-unit\">M\u03a9 at 40 \u00b0C (kV + 1 rule \u2014 pre-1970 windings; modern form-wound: 100 M\u03a9; random-wound &lt;1 kV: 5 M\u03a9)<\/span>';\n        $('vc-r-corrected').innerHTML = fmt(ir40, 1) + ' <span class=\"vc-rcard-unit\">M\u03a9<\/span> <span class=\"vc-rcard-unit\">(from ' + fmt(ir1, 1) + ' M\u03a9 at ' + fmt(tempC, 0) + ' \u00b0C)<\/span>';\n        $('vc-r-tempfactor').innerHTML = fmt(corrFactor, 4);\n        $('vc-r-pi').innerHTML = piText;\n        $('vc-r-testvolt').innerHTML = getTestVoltage(voltage);\n\n        \/\/ Trending recommendation\n        var trending = '';\n        if (ir40 >= rMin * 10) {\n            trending = '<strong>Healthy insulation.<\/strong> Continue routine testing at 6\u201312 month intervals. Record values for trend analysis.';\n        } else if (ir40 >= rMin) {\n            trending = '<strong>Adequate but declining.<\/strong> Increase testing frequency to every 3\u20136 months. Investigate if values drop >25% between tests. Consider cleaning or drying the winding.';\n        } else {\n            trending = '<strong>Below minimum.<\/strong> Do not energize. Investigate: check for moisture, contamination, or damage. Clean\/dry the winding and retest. If still failing, the winding may need repair or replacement.';\n        }\n        if (age === 'old') {\n            trending += ' <em>Note: aged motors may show lower readings \u2014 compare with the machine\\'s own historical trend.<\/em>';\n        }\n        $('vc-r-trending').innerHTML = trending;\n\n        $('vc-results').classList.add('vc-visible');\n    }\n\n    $('vc-form').addEventListener('input', calculate);\n    $('vc-form').addEventListener('change', calculate);\n\n    $('vc-copy-btn').addEventListener('click', function() {\n        var text = 'Insulation Resistance Interpretation\\n\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\n' +\n            '1-min IR: ' + $('vc-ir1').value + ' M\u03a9\\n' +\n            'Motor Voltage: ' + $('vc-voltage').value + ' V\\n' +\n            'Temperature: ' + $('vc-temp').value + ' \u00b0C\\n' +\n            'Corrected @ 40\u00b0C: ' + $('vc-r-corrected').textContent + '\\n' +\n            'Minimum: ' + $('vc-r-minimum').textContent + '\\n' +\n            'PI: ' + $('vc-r-pi').textContent + '\\n' +\n            'Verdict: ' + $('vc-r-verdict').textContent + '\\n' +\n            '\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\nvibromera.eu';\n        if (navigator.clipboard) {\n            navigator.clipboard.writeText(text).then(function() {\n                var btn = $('vc-copy-btn');\n                btn.classList.add('vc-copied');\n                btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><polyline points=\"20 6 9 17 4 12\"\/><\/svg> Copied!';\n                setTimeout(function() { btn.classList.remove('vc-copied'); btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy'; }, 2000);\n            });\n        }\n    });\n\n    document.querySelectorAll('.vc-section-toggle').forEach(function(btn) {\n        btn.addEventListener('click', function() {\n            var section = this.closest('.vc-section');\n            section.classList.toggle('vc-open');\n            this.setAttribute('aria-expanded', section.classList.contains('vc-open'));\n        });\n    });\n\n    var faqData = [\n        { q: 'What is the \"kV + 1\" rule?', a: '<p>IEEE Std 43 recommends a minimum 1-minute insulation resistance (at 40 \u00b0C) of <strong>(kV + 1) M\u03a9<\/strong>, where kV is the rated line-to-line voltage in kilovolts. This is a minimum \u2014 healthy motors typically read much higher.<\/p>' },\n        { q: 'Why correct for temperature?', a: '<p>Insulation resistance decreases as temperature increases (approximately halves every 10 \u00b0C). To compare readings taken at different temperatures, normalize to 40 \u00b0C standard reference.<\/p>' },\n        { q: 'What is Polarization Index?', a: '<p>PI is the ratio of 10-minute to 1-minute IR readings. It indicates how well the insulation absorbs charge. A low PI (&lt;2) suggests moisture or contamination. Thermoset insulation may show very high PI (&gt;5) which is normal.<\/p>' },\n        { q: 'Should I test hot or cold?', a: '<p>Both have value. Cold readings (motor off for >8 hours) are best for trending. Hot readings can reveal problems masked when cold. Always record the temperature and normalize to 40 \u00b0C.<\/p>' },\n        { q: 'What causes low insulation resistance?', a: '<p>Common causes: moisture absorption, contamination (oil, dust, chemicals), insulation degradation from aging or overheating, physical damage, and cracked insulation from thermal cycling.<\/p>' }\n    ];\n    var faqList = $('vc-faq-list');\n    faqData.forEach(function(faq) {\n        faqList.innerHTML += '<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\"><span>' + faq.q + '<\/span><svg class=\"vc-faq-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\">' + faq.a + '<\/div><\/div><\/div>';\n    });\n    faqList.addEventListener('click', function(e) {\n        var btn = e.target.closest('.vc-faq-q');\n        if (!btn) return;\n        btn.closest('.vc-faq-item').classList.toggle('vc-open');\n    });\n\n    calculate();\n})();\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>C\u00f4ng c\u1ee5 tr\u1ef1c tuy\u1ebfn mi\u1ec5n ph\u00ed \u0111\u1ec3 ph\u00e2n t\u00edch \u0111i\u1ec7n tr\u1edf c\u00e1ch \u0111i\u1ec7n \u0111\u1ed9ng c\u01a1 theo ti\u00eau chu\u1ea9n IEEE 43. T\u00ednh to\u00e1n \u0111i\u1ec7n tr\u1edf t\u1ed1i thi\u1ec3u cho ph\u00e9p, hi\u1ec7u ch\u1ec9nh nhi\u1ec7t \u0111\u1ed9, ch\u1ec9 s\u1ed1 ph\u00e2n c\u1ef1c v\u00e0 \u0111\u00e1nh gi\u00e1 \u0111\u1ea1t\/kh\u00f4ng \u0111\u1ea1t.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100138","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/vi\/wp-json\/wp\/v2\/calculator\/100138","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/vi\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/vi\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":2,"href":"https:\/\/vibromera.eu\/vi\/wp-json\/wp\/v2\/calculator\/100138\/revisions"}],"predecessor-version":[{"id":102460,"href":"https:\/\/vibromera.eu\/vi\/wp-json\/wp\/v2\/calculator\/100138\/revisions\/102460"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/vi\/wp-json\/wp\/v2\/media?parent=100138"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/vi\/wp-json\/wp\/v2\/categories?post=100138"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/vi\/wp-json\/wp\/v2\/tags?post=100138"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}