Applications
3.9 Safety-related applications of 3VA molded case circuit breakers
3VA molded case circuit breakers with IEC certificate
Manual, 03/2019, A5E03603177010-03
183
3.9
Safety-related applications of 3VA molded case circuit breakers
The 3VA molded case circuit breakers can be used in safety-related applications (up to
Category 2 and PL d according to ISO 13849-1 and SIL 2 according to IEC 62061).
As the molded case circuit breaker has no diagnostic capability, such as mirror contacts, it
cannot be used as a second function channel in the safety function. Neither is is practical to
trip the molded case circuit breaker every time a safety request occurs, as it has to be reset
manually. However it is possible to use the molded case circuit breaker as a "test device
output". When combined with a contactor, this corresponds to Category 2 according to
ISO 13849-1 and can therefore achieve up to PL d. According to IEC 62061, a hardware
fault tolerance (HFT) of 0 can be assumed and up to SILCL 2 can therefore be achieved.
Category 2 can be implemented if the contactor is monitored with the evaluation unit and a
sufficiently prompt fault response (welding of main contacts) takes place in the event of
contactor failure. The molded case circuit breaker is immediately tripped by an undervoltage
release in the event of a fault. It is therefore a single-channel architecture with a specified
fault reaction.
Moreover, the power contactor and the molded case circuit breaker constitute proven
components according to ISO 13849-2.
DANGER
Danger of death due to undetected fault cluster
Undetected fault clusters can result in life-threatening situations in the application.
In order to avoid an undetected fault cluster, the molded case circuit breaker must be tested
after 6 to 12 months at the latest.
Documentary evidence of the tests performed must be kept by the user during the period of
use.
The set delay time has an effect on the maximum response time.
DANGER
Danger of death due to excessively long delay time
The delay time set on the molded case circuit breaker has an effect on the maximum
response time.
The user must ensure that this response time in the event of a fault is sufficiently short
based on the risk assessment.
You can find details and calculation examples in the FAQs on the Internet
https://support.industry.siemens.com/cs/ww/en/view/40349715
). The B10(d) values
https://support.industry.siemens.com/cs/ww/en/view/109738685
) of the 3VA molded case
circuit breakers are also listed there.