Motors occasionally draw excess current causing overload conditions, overheating as well as phase failures. A reliable means of protection is hence required to shield the motor, motor branch circuit and its components from such situations. Overload relays available on the market offer the most steadfast safety options to prevent damages from overloading. These overload relays are typically categorized into two types namely, Thermal overload relays and Electronic overload relays. Manufactured as economic electromechanical protection devices, the thermal overload relays guarantee the safety of main power circuits while the electronic overload relays are capable of protecting motors with high precision and accuracy.

Unlike other protection devices, ABB delivers impeccable and more refined overload relays with great benefits including, but not limited to, reliability in protecting motors, easiness to create starters, matching the ABB contactors with optimized design, minimized logistic expenses of electronic overload relays, and availability of single mounting kits. Both thermal and electronic overload relays possess the ability to form a compact starting solution combined with ABB contactors.

Incorporated with bimetallic tripping elements, the thermal overload relays function accordingly by bending the tripping elements and changing the switching position in the event of an overload. These three pole overload relays can be employed for both single and three phase motor overload protection by either directly connecting to the motor circuit or by feeding through a current transformer. Thermal overload relays mostly use the tripping class 10 while having an adjustable current setting range which trips at 125% setting value. Moreover, the thermal overload relays provide overload protection with phase loss sensitivity standardized according to IEC/EN 60947-4-1. Additionally, these relays comprise with temperature compensation up to +60°C and also consist of selectable manual or automatic reset. Another feature presented in this product is the TEST and STOP function with trip indication on the front side which ensures the smooth handling of the device.

As opposed to the orthodox bimetallic overload protection, the electronic overload relays use magnetic trip function to disconnect the system during an overload condition. Accredited in accordance with IEC/EN 60947-4-1, these three pole devices offer many benefits such as low power consumption, recyclable material usage, high accuracy, low cost and low heat dissipation among others. Designed with selectable trip class (10E, 20E, 30E), the electronic overload relays provide an improved structure by installing three trip classes in a single device. In addition, the temperature compensation of electronic overload relays is maintained up to +70°C, ensuring the device performance.

Consequently, with many special features and a wide range of accessible items, ABB’s overload relays are considered the top-quality products available in the market to assure the protection of motors as well as its components to the highest degree.



  1. 2022. Thermal Overload Relays, Tripping Class 20. [online] Available Here: [Accessed 6 January 2022].
  2. Low Voltage Products. 2022. Thermal overload relays. [online] Available Here: [Accessed 6 January 2022].
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