SHORT ANSWER
Do not select the model without five basic data.
The load current, system and pole configuration, calculated short-circuit current at the installation point, need for the protection unit and coordination with upper and lower protection elements must be known for moulded-case circuit breaker (MCCB) selection.
Sigma states that the moulded-case circuit breaker (MCCB) product family is offered with a nominal current range of 16A–1600A and options of 1, 2, 3, or 4 pole numbers. The exact product code must be verified through the project calculation, panel conditions, and the latest technical documentation of the relevant model.
This guide is for pre-selection. Final short-circuit, cable protection, selectivity and coordination control must be performed by a qualified electrical engineer using project data.
Visual Separation
Product family
Separate according to application.
The function and application point of similar-looking protective devices differ. Visual comparison is only a preliminary guide.
01Main distribution and high current
moulded-case circuit breaker (MCCB); current, breaking capacity, pole and trip unit are selected together.
02Final circuit protection
miniature circuit breaker (MCB) is considered for overload and short-circuit protection in smaller circuits.
03Residual current function
Residual current protection, moulded-case circuit breaker (MCCB) selection is not replaced; it is also considered in the protection scheme.
SELECTION CRITERIA
Every value on the label
answers a separate question.
A single high value does not mean the product is suitable for the project. All criteria should be checked together.
| Control | What is determined? | Why is it important? |
|---|---|---|
| 1. rated current and thermal adjustment | Current value, based on load calculation, cable carrying capacity and operating conditions. | It ensures that the cable and connected system are protected within the correct limit for overload protection. |
| 2. number of poles | Need for 1P, 2P, 3P or 4P; requirement for opening phase and neutral together. | The distribution system and project specifications match the switching arrangement. |
| 3. Short circuit breaking capacity | The Icu/Ics value appropriate to the calculated possible short-circuit current at the point where the circuit breaker is installed. | In order for the circuit breaker to reliably interrupt the fault current, breaking capacity should not be below the calculated value. |
| 4. trip unit | Fixed or adjustable thermal-magnetic; electronic protection options if required. | Provides protection suitable for the load characteristics, initial starting currents, and adjustment requirements. |
| 5. Coordination and selectivity | Cooperative behavior of upper and lower protective elements. | Helps the closest faulty element to trip and reduces unnecessary wide area outages. |
| 6. Environment and accessories | panel temperature, installation type, connection and remote trip/auxiliary contact requirements. | Ensures proper capacity and functionality under the product's actual operating conditions. |
APPLICATION FLOW
Four steps from smart pre-selection to product code.
- 01
Collect project data
Prepare a single-line diagram, load current, voltage, cable cross-section, pole configuration, and short-circuit calculation at the installation point.
- 02
Determine the protection type
Evaluate the requirement for electronic trip unit according to the load characteristic, with fixed or adjustable thermal-magnetic protection.
- 03
Check coordination tables
Use the manufacturer's current selection and coordination data for upper and lower protective elements.
- 04
Verify the code with the document
Frame size, number of poles, breaking capacity, adjustment range and accessories verify on the same product code.
COMMON MISTAKES
Only "smart pre-selection"
Do not be content with the answer.
The actual protection performance of the compact circuit breaker depends on project data that are interrelated.
Skip short-circuit calculation
Selecting the product without comparing the breaking capacity with panel or the calculated short-circuit current at the installation point is not safe.
Adjustable and fixed types are equivalent
Adjustment requirements, load characteristics, and coordination objectives determine which trip unit is appropriate.
Assume pole configuration
Neutral switching and system structure must be verified according to project specifications.
Select code with old panel
Series and technical data may be updated. The official current manual and product code should be checked before ordering.
SHORT QUESTIONS
Pre-offer requirements.
Is selecting the highest kA value always correct?
breaking capacity, calculated short-circuit current at the installation point should be met. A higher value does not necessarily mean the selection is correct; coordination, body, setting and cost are evaluated together.
What is the difference between thermal-magnetic and electronic moulded-case circuit breaker (MCCB)?
Thermal-magnetic types provide overload and short circuit protection using a mechanical/electromagnetic trip mechanism. Electronic types can offer wider adjustment and model-dependent additional protection options. The requirement is determined according to the project and load characteristics.
What information should be sent for the quotation?
rated current, number of poles, operating voltage, requested breaking capacity, trip unit, quantity and required accessories must be shared. If available, single line diagram and existing product code will speed up the process.
UNVERIFIED SOURCES