A circuit breaker’s kA marking describes a specified short-circuit rating under stated test conditions. One kiloampere equals 1,000 amperes. Read the declared rating together with the applicable standard, rated voltage and AC/DC conditions; it is different from the normal current rating in amperes.
إذا كنت تختار قاطعًا كهربائيًّا للوحة أو آلة أو منشأة، فإن هذا الرقم ليس اختياريًّا. فعند حدوث ماس كهربائي، يمكن أن يقفز تيار العطل إلى آلاف أو حتى عشرات الآلاف من الأمبيرات في أجزاء من الثانية. إذا كانت السعة المقننة للقاطع بالكيلو أمبير (kA) منخفضة جدًّا، فقد لا يتمكن من إزالة العطل بأمان — مما قد يؤدي إلى تلف المعدات أو خطر نشوب حريق أو الفشل في اجتياز الفحص.
This guide explains kA markings, the ratings to verify for different breaker types, and the checks an electrical professional needs for selection.
Check which short-circuit rating the manufacturer declares. Icn applies to relevant household and similar circuit breakers; Icu and Ics apply to relevant industrial circuit breakers. Their test duties differ, so these markings should not be treated as interchangeable.
على سبيل المثال:
لا علاقة لهذه القيمة بتيار التشغيل العادي. فقد لا يتجاوز التيار في داربتك 20 أمبير أو 100 أمبير أثناء التشغيل العادي، لكن تيار العطل قد يصل إلى أعلى بمئات المرات للحظة وجيزة. ولهذا السبب يُعد تصنيف «kA» من مواصفات السلامة — وليس من مواصفات الراحة.
Manufacturer documentation may identify different short-circuit ratings, including:
A number alone does not establish that a breaker can remain in service after a fault. Follow the manufacturer’s inspection and replacement instructions. Verify the installation’s prospective short-circuit current against the applicable declared rating or an exact manufacturer-documented coordinated combination.
يوجد قاطع قيمتان مختلفتان تمامًا للتيار المسموح به:
A breaker can have an appropriate normal current rating and still have insufficient short-circuit breaking capacity. Both ratings need to be checked; a correct ampere rating does not establish suitability for the available fault current.
Breaker categories do not establish universal kA ranges. Verify the selected model’s declared ratings, voltage and applicable standard.
جدول مقارنة سريع
| Breaker information | ما الذي يجب التحقق منه |
| Household and similar circuit breaker | Applicable standard, declared Icn and rated voltage |
| Industrial circuit breaker | Applicable standard, declared Icu and Ics at the specified voltage |
| Coordinated breaker combination | Exact device references, permitted conditions and manufacturer-verified combination tables |
Compare the selected model’s declared ratings with the calculated prospective short-circuit current at its installation point. Where a coordinated combination is used, verify the exact devices and permitted conditions in the manufacturer’s documentation.
MCB breaking-capacity ratings vary by model, voltage and applicable standard. Small normal loads do not establish a low prospective short-circuit current.
تشمل الأحمال الشائعة ما يلي:
Supply characteristics and circuit impedance affect prospective fault current. Verify the declared rating at the installation point rather than selecting from a generic category range.
For an MCCB, check the declared Icu and Ics at the required voltage, together with its current rating and protection settings.
وتُستخدم على نطاق واسع في:
Frame size and application alone do not establish breaking capacity or suitability for continued service after a fault. Reassess fault current and coordination when the supply system changes.
An ACB may be used in main distribution applications, but its ratings depend on the selected model and voltage. Do not assume a universal kA rating from the breaker category.
Verify the manufacturer’s declared short-circuit ratings, protection settings and coordination data for the selected ACB and its installation.
Insufficient short-circuit breaking capacity is a serious specification issue. Verify the prospective fault current and the selected breaker’s applicable rating, or a manufacturer-documented coordinated combination. Breaking capacity alone does not establish overall installation safety, selectivity, assembly suitability or compliance with the project’s applicable requirements.
المصدر: من تصميم Freepik
يتبع اختيار سعة الكبح الصحيحة منطقاً هندسياً واضحاً.
(1) تحديد الحد الأقصى لتيار العطل
يُعد تيار الدائرة القصيرة المتاح عند نقطة التركيب هو القيمة المرجعية. احصل على هذه القيمة أولاً — فهي القيمة المرجعية للاختيار.
(2) النظر في التوسع في المستقبل
Changes to transformers, generators or other supply arrangements can change fault levels. Reassess the fault study and coordination when the electrical system changes; do not assume that every load increase has the same effect.
iii) مطابقة التصنيف مع التطبيق
Starting and inrush currents affect the selection of trip characteristics and protection settings. They do not, by themselves, determine the required short-circuit breaking capacity. Determine prospective fault current from the electrical system and installation conditions. A kA breaking-capacity rating is not a surge-protection rating.
(4) التنسيق مع أجهزة الحماية الأخرى
A higher kA rating does not guarantee selective tripping. Selectivity depends on the exact upstream and downstream devices, their settings and the fault-current range. Check manufacturer coordination tables to establish whether selectivity is total or limited to a stated current.
(5) اتباع إرشادات الشركة المصنعة
يتم التحقق من قيم السعة القصوى من خلال الاختبارات. يجب دائمًا الالتزام بالقيم المعتمدة والمعايير الدولية للكهرباء (IEC) أو المعايير المحلية المعمول بها. تختلف طرق اختبار العلامات التجارية لأجهزتها. يجب اتباع إرشادات الشركة المصنعة والمعايير المعمول بها.
عند مراجعة أو اختيار قاطع الدائرة، يرجى مراعاة النقاط التالية:
Breaking capacity is one part of circuit-breaker selection. The installation also needs appropriate voltage and current ratings, trip characteristics, coordination and suitability for the service conditions. Have a qualified electrical professional assess the system and verify the exact manufacturer’s documentation before installation.
قبل اتخاذ القرار النهائي بشأن اختيار أي قاطع كهربائي:
For an أوماج quotation, provide the application requirements and the model information to be checked. Confirm the applicable product datasheet and declared ratings before specifying a breaker.
Prospective fault current depends on the supply arrangement and circuit impedance, not only the connected load. A qualified electrical professional should determine the fault level at each installation point and reassess it when the supply system changes.
A replacement needs checks for voltage, current rating, trip characteristics, physical compatibility and coordination. A higher breaker breaking-capacity rating does not, by itself, establish the required assembly rating. Assess the assembly against the actual prospective fault current and applicable protection conditions.
kA is a unit of current. kAIC is used to express an interrupting rating in kiloamperes. Icn, Icu and Ics identify different short-circuit ratings or test duties under their applicable standards. Compare the declared value, voltage, standard and test conditions; these markings should not be treated as interchangeable.
Yes. Breaking capacity is only one selection criterion. An assessment also needs to consider the assembly, voltage and current ratings, protection settings, coordination and applicable installation requirements. A sufficient kA value alone does not establish compliance.
