{"id":2611,"date":"2026-11-04T17:12:00","date_gmt":"2026-11-04T09:12:00","guid":{"rendered":"https:\/\/www.zishengelectric.com\/?p=2611"},"modified":"2026-11-04T10:21:48","modified_gmt":"2026-11-04T02:21:48","slug":"how-to-read-%c2%b12-x-2-5-on-a-transformer-tap-schedule","status":"publish","type":"post","link":"https:\/\/www.zishengelectric.com\/fr\/how-to-read-%c2%b12-x-2-5-on-a-transformer-tap-schedule.html","title":{"rendered":"How to Read \u00b12 \u00d7 2.5% on a Transformer Tap Schedule"},"content":{"rendered":"

On a conventional symmetric schedule, \u00b12 \u00d7 2.5% means two steps above the nominal tapping voltage and two below it, each step equal to 2.5% of nominal. Including the nominal position, that gives five positions. When asking Zisheng Electric to quote a transformer, request the actual voltages alongside the percentages. A five-line table makes a discrepancy easier to spot than a plus sign on a catalogue sheet.<\/p>\"Technical

Translate the shorthand into volts<\/h2>

Consider a hypothetical 11,000 V primary winding with the above schedule. One step is 275 V. The winding tapping voltages are shown below in ascending order. These are voltage designations, not instructions to move a switch. The manufacturer\u2019s position numbers and physical sequence must be read from its own approved drawing.<\/p>
Offset from nominal<\/th>Primary tapping voltage<\/th><\/tr><\/thead>
\u22125%<\/td>10,450 V<\/td><\/tr>
\u22122.5%<\/td>10,725 V<\/td><\/tr>
Nominal<\/td>11,000 V<\/td><\/tr>
+2.5%<\/td>11,275 V<\/td><\/tr>
+5%<\/td>11,550 V<\/td><\/tr><\/tbody><\/table>

The highest tapping voltage is five percent above nominal. The span between lowest and highest is ten percent of nominal. Recording only \u201c10% range\u201d loses information. A bidder could interpret that as an asymmetric arrangement entirely below nominal. Ask for both endpoints, the nominal position, step size and the winding on which the taps are provided.<\/p>

Which voltage does the plus sign describe?<\/h2>

In this example the plus sign describes a primary winding tapping voltage. It does not promise a higher secondary output at the same incoming voltage. For a fixed secondary winding, selecting more primary turns gives a lower ideal secondary voltage at unchanged input. The intended use of a higher primary tapping voltage is to accommodate a correspondingly higher supply while maintaining approximately the target secondary voltage.<\/p>

For example, take an idealized 11,000\/400 V ratio. With 11,550 V applied to the 11,550 V tap, the ideal secondary voltage is 400 V. With 11,000 V applied to that same tap it is about 381 V, calculated as 400 \u00d7 11,000 \/ 11,550. Actual loaded terminal voltage depends on impedance, load and power factor. The arithmetic explains the direction of the change. It does not select a field setting or permit operation outside the approved rating.<\/p>

Schneider Electric\u2019s voltage adjustment tap explanation<\/a> gives a manufacturer example of the relationship between supply and secondary voltage. Compare the actual position table for the offered equipment before assigning any universal meaning to \u201cposition one.\u201d<\/p>\"EPC

Separate coverage from the way taps are changed<\/h2>

Two quotations can offer the same five voltages and still serve different operating needs. A de-energized arrangement requires the specified outage and safe isolation. An on-load tap changer is designed to change taps while carrying load within its rating. The tap changer selection guide<\/a> covers that choice. The percentages alone do not establish which mechanism, controls or operating procedure is included.<\/p>

Ask whether full rated apparent power is available on every required tap. A percentage schedule establishes the voltage steps. It does not by itself establish current limits or permissible loading at the extreme positions. Obtain the manufacturer\u2019s tapping table with rated voltage, current and power for the required duty. Carry the approved values into the nameplate and rating-record review<\/a>.<\/p>

Give the bidder a supply range it can check<\/h2>

State the normal, minimum and maximum incoming voltage on a consistent basis, together with frequency, required secondary voltage and the relevant load cases. Distinguish occasional deviations from sustained operating conditions. If the owner requires a particular secondary voltage band, state where it is measured and under what load. The transformer terminals and a remote motor bus may have different voltages.<\/p>

For a 110 kV\u2013115 kV power transformer<\/a> enquiry, give Zisheng Electric the utility voltage schedule and any restrictions on outages. Ask the bidder to return one row per position and identify any project operating case the proposed range cannot cover. Procurement can then resolve the gap before the drawing is released for manufacture.<\/p>","protected":false},"excerpt":{"rendered":"

Translate a tap range into actual primary voltages, check the nominal position and compare two transformer bids against the supply range specified for your project.<\/p>","protected":false},"author":1,"featured_media":2131,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"themepark_post_bcolor":"#f5f5f5","themepark_post_width":"1022px","themepark_post_img":"","themepark_post_img_po":"left","themepark_post_img_re":false,"themepark_post_img_cover":false,"themepark_post_img_fixed":false,"themepark_post_hide_title":false,"themepark_post_main_b":"","themepark_post_main_p":100,"themepark_paddingblock":false,"footnotes":""},"categories":[4],"tags":[410,581,582],"class_list":["post-2611","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-epc-procurement","tag-tap-schedule","tag-transformer-voltage-ratio"],"metadata":{"_edit_lock":["1793790363:1"],"_thumbnail_id":["2131"],"_edit_last":["1"],"themepark_seo_title":["Transformer Tap Percentages Explained | EPC Bid Review"],"themepark_seo_description":["Translate a tap range into actual primary voltages, check the nominal position and compare two transformer bids against the supply range specified for your project."],"themepark_seo_keyword":["transformer tap percentages, EPC procurement"],"catce":["sidebar-widgets4"],"views":["120"]},"medium_url":"https:\/\/www.zishengelectric.com\/wp-content\/uploads\/2026\/09\/transformer-rating-record-reconciliation-e1789980992635-300x169.png","thumbnail_url":"https:\/\/www.zishengelectric.com\/wp-content\/uploads\/2026\/09\/transformer-rating-record-reconciliation-e1789980992635-150x150.png","full_url":"https:\/\/www.zishengelectric.com\/wp-content\/uploads\/2026\/09\/transformer-rating-record-reconciliation-e1789980992635.png","_links":{"self":[{"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/posts\/2611","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/comments?post=2611"}],"version-history":[{"count":1,"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/posts\/2611\/revisions"}],"predecessor-version":[{"id":2612,"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/posts\/2611\/revisions\/2612"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/media\/2131"}],"wp:attachment":[{"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/media?parent=2611"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/categories?post=2611"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.zishengelectric.com\/fr\/wp-json\/wp\/v2\/tags?post=2611"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}