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Information 392e

Defined Current Sensitive Thermal protector of Type SZ1

Application:

The current sensitive thermal protector type SZ1 with normally closed contacts is utilised for overheating protection of all electric equipment or devices, especially to safeguard transformers according to EN 60 742. The type SZ1 is sensitive for temperature as well as for currents. Therefore it is recommended in all cases of a dramatic rise of temperature, due to an overload current, e.g. in case of short circuit.

Design:

The thermal protector SZ1 is based on the well proven mechanism of Thermik’s product series 01. A defined current-sensitivity is reached by an integrated series resistor

R

S . Version: SZ1 with insulation cap
Diameter d 9.4 mm Height h 5.0 mm Length of insulation cap

Operation:

l 19.0 mm dimensions (average) If, in the case of overheating or increase in current, the rated switching temperature of the bimetallic disc is reached, this suddenly snaps over and opens the contact. Automatic resetting after a significant temperature drop. TP of Type SZ1 R
S U

Series Resistor R

S

: R

L The series resistor R
S has to be adapted to each application. To protect an electrical apparatus, the response time should be less than 20 seconds in case of a short circuit. In order to guarantee this ideal response time, a heating performance of R
S between 5 W and maximal 10 W is recommended. The table on the next side will help to find an optimal resistor R
S . Due to different possibilities of adapting the protector to the electrical device, experimental tests with different protectors are recommended.

Features:

Quick response sensitivity: featured by the metal housing and small protector mass Defined response time:
S Excellent long term performance : due to fine-silver contacts. Reproducible switching temperature values due to tempered, electrically and mechanically unstressed bimetallic disc Instantaneous switching: with constant contact pressure over the whole temperaturerange Very short bounce times:
Thermik Gerätebau GmbH ? P.O. Box 101980 ? D-75119 Pforzheim ? Germany ? Phone: +49 (72 31) 60 04 -0 ? Fax: +49 (72 31) 60 04 -100