UL1077 Supplementary Protector

UL1077 Supplementary Protector

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.

5SY Supplementary Protector Benefits

  • High rated breaking capacity of up to 14,000 A

  • Identical terminals at both sides for an optional infeed from the top or the bottom

  • No tool required for mounting or dismounting

  • Separate switch position indication

Supplementary Protectors

5SY4 - Supplementary Protectors (0.3 - 63A, AC)

UL 1077

5SP4 - Supplementary Protectors (80 - 125A, AC)

Supplementary Protectors

5SY5 - Supplementary Protectors (0.3 - 63A, AC/DC)

5SX2 - Supplementary Protectors (0.3 - 63A, AC)

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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