Supplementary Protectors

Siemens' UL 1077 Supplementary Protectors are designed to provide additional protection along with a branch circuit protection device. Since our Supplementary protectors are made to trip faster than a standard UL 489 Circuit Breaker they are able to provide additional protection for more sensitive devices inside the panel. Supplementary protectors can used in a number of industrial applications such as to provide selectivity for multiple motor control circuits on the secondary side of a control transformer or power supply by allowing the user to quickly find the problem circuit should a fault occur with out having to shut down all of the other control circuits. Supplementary protectors may also be used as a local disconnecting means inside the panel when a branch circuit protection device is already present.

Tripping characteristic

Supplementary protectors are equipped with a delayed overload/time-dependent thermal release (thermal bimetal) for low overcurrents and with an instantaneous electromagnetic release for high overload and short-circuit currents.  The thermal trip point on all versions is 1.13 to 1.45 times the supplementary protector rating.

  • Tripping characteristic A, -5: To protect very sensitive circuits such as semiconductors. Magnetic trip point - 2 to 3 times supplementary protector rating.  

  • Tripping characteristic B, -6: For European residential circuit protection.  Also for protection of computers and electronic equipment. Magnetic trip point. 
     - 3 to 5 times supplementary protector rating. 

  • Tripping characteristic C, -7: For general device protection in control circuits and all other supplementary circuit protection systems. Magnetic trip point
    - 5 to10 times supplementary protector rating.

  • Tripping characteristic D, -8: For protection of high inrush loads. Magnetic trip point - 10 to 20 times supplementary protector rating.  

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