{"id":2615,"date":"2026-11-05T10:18:22","date_gmt":"2026-11-05T02:18:22","guid":{"rendered":"https:\/\/www.zishengelectric.com\/?p=2615"},"modified":"2026-11-05T10:18:28","modified_gmt":"2026-11-05T02:18:28","slug":"dry-type-transformer-insulation-class-vs-temperature-rise","status":"publish","type":"post","link":"https:\/\/www.zishengelectric.com\/fr\/dry-type-transformer-insulation-class-vs-temperature-rise.html","title":{"rendered":"Dry-Type Transformer Insulation Class vs Temperature Rise"},"content":{"rendered":"

A dry-type transformer\u2019s insulation class describes the thermal capability of its insulation system. Temperature rise describes how much warmer the winding becomes than its cooling medium under specified conditions. They are related, but one number cannot replace the other. When requesting a Zisheng Electric quotation, put both fields on the enquiry so the offered thermal design can be reviewed against your actual installation.<\/p>\n\"Indoor\n

Read the temperature fields separately<\/h2>\n

For an EPC procurement engineer, the first task is to identify what each figure represents. A temperature in degrees Celsius is an absolute temperature. A rise in kelvin is a temperature difference. A rise of 100 K is numerically the same interval as 100\u00b0C, but it does not mean the winding operates at an absolute temperature of 100\u00b0C.<\/p>\n
Field<\/th>Meaning<\/th>Buyer\u2019s check<\/th><\/tr><\/thead>
Insulation thermal class<\/td>Thermal classification of the complete electrical insulation system<\/td>Ask for the numerical class and applicable design standard, not only a letter.<\/td><\/tr>
Average winding temperature rise<\/td>Average winding temperature above the specified cooling-medium reference<\/td>Request the guaranteed rise at the stated load and cooling arrangement.<\/td><\/tr>
Winding hot spot<\/td>The hottest location in the winding insulation system<\/td>Confirm how its temperature is assessed and controlled.<\/td><\/tr>
Cooling-air temperature<\/td>The air condition used for the thermal design<\/td>Identify the intake location and the applicable maximum and average conditions.<\/td><\/tr><\/tbody><\/table>\n

The hottest part of a winding can be warmer than the winding average. Consequently, subtracting the average rise from the insulation-class number does not establish an allowable room temperature. It omits the hot-spot relationship and the design\u2019s specified operating conditions.<\/p>\n

Why a higher class does not automatically mean a cooler transformer<\/h2>\n

Schneider Electric\u2019s low-voltage transformer guidance shows that a 220\u00b0C insulation system can be used with different specified rises, including 150\u00b0C, 115\u00b0C and 80\u00b0C. This illustrates the distinction between insulation capability and thermal design. Those combinations belong to that product context and should not be copied as a universal IEC limit table.<\/p>\n

Consider two hypothetical offers for the same required kVA, voltage and natural-air cooling duty. Both declare the same numerical insulation class. Offer A guarantees an average rise of 100 K and Offer B guarantees 80 K under identical agreed conditions. The second offer promises a lower average rise at that duty. The shared insulation class alone would not reveal this difference.<\/p>\n

That comparison does not establish an overload allowance, a quantified life extension or a percentage energy saving. Each claim needs its own design evidence. In particular, request guaranteed losses separately if energy consumption is part of the purchase decision.<\/p>\n\"Technical\n

Bring the room and enclosure into the comparison<\/h2>\n

An outdoor weather figure may differ from the air reaching a transformer inside an enclosure or electrical room. Restricted ventilation and recirculated warm air can change the cooling conditions. Give every bidder the same room arrangement, enclosure requirements, site elevation and operating load before comparing thermal guarantees.<\/p>\n

The transformer room layout guide<\/a> explains the physical interfaces to coordinate. Ask the supplier to state whether the offered kVA and rise apply to the enclosed assembly or another tested configuration. If fans are optional, obtain separate guaranteed duties for natural and forced-air operation.<\/p>\n

What to ask for before datasheet approval<\/h2>\n