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Siemens Thermal Overload Relays

A thermal overload ralay is a device to protect an electrical device like a motor/generator from catching fire/burning out due to excessive heat produced during operation. The relay has a bi-metallic contact that operates with temperature. When the temperature of the system goes above a pre-set value, the contact goes from closed position to open, and the power supply to the circuit is cut and the device is saved from damages. So it keeps the system with in the safe operating temperatures. You may find thermal relays for different temperature values, based on the operating range of your equipment.

Siemens provides 3UA series of overload relays based on the concept of bimetallic strips. The bimetallic thermal relay consists of a small bimetallic strip that is heated by an element connected in series with the supply. When the current rises above a preset value, the movement of the strip releases a catch which opens the trip contacts.

3UA Series Overload Relays are suitable for overload and phase – failure protection of AC motors with frequency of 50/60Hz, voltage up to 690 ~ 1000V, current up to 0.1 ~ 400A under 8 – hours duty or uninterrupted duty. The relays are also suitable for overload protection of DC magnet and DC motors.

The relays comply with IEC947-4, VDE0660 and GB14048. Several functions provided by these relays are: phase-failure protection, temperature compensation, ON/OFF indication and manual/automatic reset. The relays can be mounted onto contactors or installed as single units



  • 3UA series are bimetal thermal relays with release class 10A.
  • With differential phase- failure protection.
  • With continuous current adjusting scale
  • With temperature compensation
  • With ON/OFF indicator
  • With TEST(OFF) button
  • With Manual/Auto reset button
  • With Auxiliary contacts 1 NO +1 NC insulated each other
  • SIGUT – Siemens patent terminal, ensures easy and reliable connection, strong shock resistance and perfect safety protection.
  • Mounting: plug in connection with contactor or install as a single unit

Please note that Siemens being a global multinational company follows the same quality standards in all its plants across the world for the products sold globally.

We, at KMIC, provide all these series of relays from Siemens. Kindly note that all the products provided by KMIC are 100% brand new and genuine.

Please click on individual links to know more about the products.

Siemens 3UA Relays


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