SENTRON Miniature Circuit Breakers Technology

Overview

This document is Siemens's 2016 manufacturer primer on SENTRON miniature circuit breakers (MCBs). The primer identifies the magnetic trip-characteristic envelopes according to IEC 60898-1. It is under Siemens copyright; this record rests only on metadata and a short summary, not on the primer as a whole. As a manufacturer introduction, it is a reference that presents the technology of a product family rather than a general design rule.

The key information in the record is the broad magnetic operating envelopes for the referenced AC classes: class B at 3 to 5 times rated current, class C at 5 to 10 times and class D at 10 to 20 times. These ranges are broad class bounds showing at which current multiples the instantaneous (magnetic) trip region of an MCB begins under short-circuit conditions. The information is taken from the 'Tripping characteristics' section.

An important limit applies: these broad class bounds are screening inputs and do not prove the selectivity of a specific pair of devices. Real selectivity verification must be done with the manufacturers' selectivity tables or trip curves for the devices concerned, together with the short-circuit current. In short, this document is useful for quickly recalling typical magnetic trip multiples of MCB classes, but it cannot be the sole basis of a protection-coordination decision.

Key points

1. The source is Siemens's 2016 SENTRON MCB manufacturer primer.
2. It identifies IEC 60898-1 magnetic trip-characteristic envelopes.
3. For the referenced AC classes the broad magnetic operating envelope for class B is 3-5 times rated current.
4. Class C: 5-10 times rated current.
5. Class D: 10-20 times rated current.
6. These broad class bounds are screen inputs, not pair-specific selectivity evidence.

Using it in design

• Use the broad class bounds (B 3-5, C 5-10, D 10-20 times) as screening inputs in a selectivity study.
• Verify selectivity claims for specific device pairs with manufacturer selectivity tables or trip curves.
• State in reports that class envelopes are not pair-specific selectivity evidence.

Who should read it

Electrical designers doing low-voltage protection and selectivity studies and engineers selecting MCB classes.

Publication details

Authors

Siemens

Publisher

Siemens

Year

2016

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation