限值表怎么查：温升、漏电流与耐压

结论：限值取决于条件，先定条件再查表

企业在自查时经常问：温升限值是多少、漏电流限值是多少。这个问题本身就不完整，因为限值不是一个固定数字。

温升限值取决于部件的类型、材料、是否可触及、接触时间；漏电流限值取决于测量类型、设备类型、应用部分的分型、正常还是故障状态；耐压试验电压取决于绝缘的位置、工作电压、绝缘配合的等级。

所以查限值的正确顺序是：先把条件确定清楚，再查对应的限值。 顺序反了，查出来的数字可能完全不适用。

温升限值

温升相关的限值要区分几类：

绕组与元件。 按绝缘材料的耐热等级确定，不同等级的允许温度不同。

可触及表面。 按表面材料和预期接触时间确定。金属表面的限值低于塑料，因为金属导热快、烫伤风险高。

与患者接触的部分。 限值通常更严，因为接触时间长且使用者可能无法感知或躲避。

元件的自身限值。 元件规格书规定的上限，可能比通用要求更严。

查温升限值时要确定的条件： 测量点是什么部件；部件的材料；是否可触及；预期接触时间；以及元件自身的规格限制。

「元件自身限值」常被忽略。 通用要求允许的温度，可能已经超出某个元件规格书的上限。两者取较严的一方。

漏电流限值

漏电流是分类最细的一项，查限值要确定：

单一故障状态的限值高于正常状态，但这不意味着可以放松——因为故障状态下的实际漏电流也会升高，两者要一起考虑。

常见的查错是混淆测量类型。 对外壳的漏电流和对患者的漏电流是不同的测量，限值也不同，用错会导致判断错误。

耐压试验

耐压试验电压的确定需要：

明确绝缘的位置。 是哪两部分之间的绝缘——网电源与外壳、网电源与应用部分、应用部分与外壳等。

确定该绝缘的工作电压。 实际承受的电压。

确定绝缘的类型。 基本绝缘、附加绝缘、加强绝缘、双重绝缘。

查对应的试验电压。

这一项的难点在于「绝缘图」的梳理 ——要把设备中所有需要考察的绝缘位置都找出来，并确定每处的类型和工作电压。设备复杂时，这项梳理本身就需要时间。

建议在设计阶段就画出绝缘图，标明各处的绝缘类型、工作电压、爬电距离和电气间隙。这份图在设计、送检、审查三个环节都用得上。

常见的查错情形

用错设备类型。 对设备的防电击类型判断有误。

用错应用部分分型。 前面专门讲过。

混淆正常与故障状态的限值。

忽略元件自身限制。 只看通用要求。

忽略材料耐热等级。 按通用表查温升，未核对实际使用的绝缘材料等级。

测量条件不对。 供电电压、环境温度、负载状态不符合要求。

忽略修正。 某些测量需要按环境条件修正。

「测量条件不对」在自测时很常见。 比如温升测试要在规定的环境温度下做，或者按实际环境温度修正到规定条件；不做修正的自测数据可能与正式测试结果差别明显。

自查时的注意点

先做条件清单。 把影响限值的条件一项项确定下来，再查表。

留余量。 自测条件不如正式测试严格，如果自测结果刚好卡在限值，正式测试很可能超。建议自查时按限值的一定比例作为内控线。

记录测量条件。 环境温度、供电电压、负载状态、测量点位置。没有条件记录的数据无法复核。

注意测量点的选择。 温升测量点要选在真正的热点，而不是容易测的地方。

核对元件规格书。 关键元件的温度、电压、电流上限。

「留余量」这一条最实际。 设计时按限值做，制造和使用中的各种变化都会吃掉余量，最终在某批产品上超标。

数据的记录

自查数据的记录建议包含：测量项目；测量条件（环境、供电、负载）；测量点位置；实测值；适用限值及其来源；判断结论；以及测量日期和人员。

「适用限值及其来源」这一项建议写清楚，因为它记录的是你按什么条件查的限值。将来如果条件判断有变（比如分型改了），可以据此快速找出受影响的项目。

爬电距离与电气间隙

这两项与耐压试验相关，但考察方式不同——耐压是施加电压看是否击穿，距离是实测几何尺寸。确定要求值需要：

工作电压。 该位置实际承受的电压。

绝缘类型。 基本、附加、加强。

污染等级。 与使用环境相关。

材料组别。 绝缘材料的耐电痕性能。

海拔。 高海拔需要修正。

「材料组别」和「污染等级」常被忽略，而它们直接影响爬电距离的要求值。用错组别可能导致设计的距离不够。

测量时还要注意路径的确定 ——爬电距离沿绝缘表面测量，遇到沟槽、筋条时的计算方式有具体规定，不是简单的直线距离。

自测设备的局限

用简易设备自测时要清楚其局限：

漏电流测试。 测量网络的阻抗特性要符合要求，用普通万用表测出的值不具可比性。

温升测量。 热电偶的粘贴方式、位置、导热影响测量结果。

耐压试验。 试验设备的电流限值和上升速率有要求。

环境条件。 温湿度会影响多项测量。

这些局限不意味着自测没有意义 ——自测能发现明显超标的问题，只是不能代替正式测试的判定。自测的定位是筛查，不是判定。

我们的做法

承接电气安全委托时，我们会先与委托方确认影响限值的关键条件：设备类型、应用部分分型、绝缘配置。这些条件确定之后，限值才有意义。

对于自查过的委托方，我们会看自查的条件记录。如果条件判断与我们的理解不同，会先讨论清楚 ——否则自查合格而正式测试不合格，双方都要花时间找原因。

如果你在准备送检，想先核对一遍限值适用的条件，可以把设备说明和电路资料发过来一起看，或者直接联系：132 4819 8029。能力范围见服务介绍，送检要求见送检要求，流程见检测流程。

English version

Conclusion. Manufacturers preparing for submission frequently ask what the temperature rise limit or leakage current limit is. The question is incomplete, because limits are not fixed numbers. Temperature rise limits depend on the type of part, its material, whether it is accessible and for how long it is contacted. Leakage limits depend on the measurement type, the equipment class, the applied part classification and whether the condition is normal or single fault. Test voltages depend on where the insulation sits, its working voltage and the grade of insulation coordination. The correct order is therefore to establish the conditions first and then look up the corresponding limit. Reversed, the number found may not apply at all.

Temperature rise limits. Several categories must be distinguished. Windings and components follow the thermal class of the insulating material, with different classes permitting different temperatures. Accessible surfaces follow the surface material and expected contact duration, with metal surfaces limited below plastics because metal conducts heat quickly and burns more readily. Parts contacting the patient carry stricter limits, since contact is prolonged and users may be unable to feel or withdraw. And components carry their own limits from their data sheets, which may be stricter than the general requirement. To look up a temperature rise limit, establish which part is measured, its material, whether it is accessible, the expected contact duration, and the component's own rating. The last is commonly overlooked: a temperature permitted by the general requirement may already exceed a component data sheet maximum, and the stricter of the two governs.

Leakage current limits. Leakage is the most finely subdivided item. Establish the measurement type, whether earth, enclosure, patient or another. Establish the equipment's protection class, which relates to supply and earthing arrangements. Establish the applied part classification, which drives patient-related limits. Establish the condition, normal or single fault. And establish the supply condition, typically a multiple of rated voltage. Single fault limits exceed normal condition limits, which does not license relaxation, since actual leakage also rises under fault and the two must be considered together. A frequent error is confusing measurement types: enclosure leakage and patient leakage are different measurements with different limits, and using the wrong one leads to the wrong conclusion.

Dielectric strength testing. Determining the test voltage requires identifying where the insulation sits, meaning between which two parts, such as mains to enclosure, mains to applied part, or applied part to enclosure; determining that insulation's working voltage, meaning the voltage it actually withstands; determining the insulation type, whether basic, supplementary, reinforced or double; and then looking up the corresponding test voltage. The difficulty lies in mapping the insulation: finding every insulation location requiring assessment and establishing its type and working voltage. In complex equipment that mapping itself takes time. Draw an insulation diagram during design, marking insulation type, working voltage, creepage and clearance at each location; it serves design, submission and review alike.

Common lookup errors. Wrong equipment class from misjudging the protection class. Wrong applied part classification, discussed separately. Confusing normal and fault condition limits. Ignoring component ratings and consulting only the general requirement. Ignoring material thermal class, reading a general table without checking the insulation actually used. Wrong measurement conditions of supply voltage, ambient temperature or load state. And omitting corrections, since some measurements require correction for ambient conditions. Wrong measurement conditions are common in self-testing: temperature rise must be measured at a specified ambient, or corrected to it from the actual ambient, and uncorrected self-test data can differ markedly from formal results.

Points for self-checking. Build a condition list first, settling each factor that affects the limit before consulting a table. Leave margin, since self-test conditions are less rigorous than formal testing and a result sitting right at the limit will probably exceed it formally; set an internal control line at a proportion of the limit. Record measurement conditions of ambient, supply, load and measurement point, since data without conditions cannot be reviewed. Choose measurement points carefully, placing temperature sensors at genuine hot spots rather than convenient locations. And check component data sheets for temperature, voltage and current maxima. Leaving margin is the most practical advice: designing to the limit means that ordinary variation in manufacture and use consumes the margin and some batch eventually exceeds it.

Recording data. Self-check records should include the measured item, conditions covering ambient, supply and load, measurement point location, measured value, the applicable limit and its source, the conclusion, and the date and personnel. Recording the limit's source is worth doing, because it captures the conditions under which you looked it up. If a condition judgement later changes, such as a revised classification, you can quickly identify the affected items.

How we handle it. For electrical safety work we confirm the key conditions with the client first: equipment class, applied part classification and insulation arrangement. Only once those are settled do limits mean anything. Where a client has self-checked we review their condition records, and where their judgement differs from ours we resolve it first; otherwise a self-check passes while formal testing fails, and both sides spend time finding out why.

Send us the equipment description and circuit documentation and we will review which conditions apply. Phone or WeChat: +86 132 4819 8029.