Siemens introduces Sirius 3RN2 series of motor protection relays |

Siemens introduces Sirius 3RN2 series of motor protection relays

October 212016
Siemens introduces Sirius 3RN2 series of motor protection relays

October 21, 2016 - Siemens is bringing a product family of thermistor motor protection relays onto the market. The Sirius 3RN2 replaces the preceding 3RN1 series, and with widths of 17.5 and 22.5 millimeters these relays require less space in a control cabinet. A standardized supply voltage reduces the number of versions. With just one device, machine manufacturers and users cover all supply voltages throughout the world. Sirius 3RN2 thermistor motor protection relays protect motors against overheating by measuring the temperatures at points at risk of overheating within the motor. PTC (positive temperature coefficient) temperature sensors are integrated into the motor windings to monitor critical overheating.

The Atex versions of the Sirius 3RN2 thermistor motor protection relays were developed with the focus on functional safety. Verification of their suitability for SIL 1 applications fulfills an important requirement of DIN EN 50495. The verification of suitability for Atex is valid for both gas-laden and dust-laden atmospheres. This makes production safe for machine manufacturers and users, even under difficult conditions, such as those found in the oil, gas and chemical industries, and in mills and sawmills.

Thermistor motor protection relays are used particularly where circuit breakers or overload relays do not provide adequate protection. In these cases, the motor may overheat, if, for example, the fan provided as standard fails or the ambient temperature exceeds the maximum defined in the assumed boundary conditions. Typical applications for thermistor motor protection relays are for a heavy start of, for example, centrifuges, braking procedures, frequent switching, such as in jogging  and reversing operations, and where there is a risk of the motor cooling being impaired by contamination, for example in the paper and textile industries and in cement works.

About Siemens

Siemens is a global technology powerhouse that has stood for engineering excellence, innovation, quality, reliability and internationality for more than 165 years. The company is active in more than 200 countries, focusing on the areas of electrification, automation and digitalization. One of the world’s largest producers of energy-efficient, resource-saving technologies, Siemens is No. 1 in offshore wind turbine construction, a leading supplier of gas and steam turbines for power generation, a major provider of power transmission solutions and a pioneer in infrastructure solutions as well as automation, drive and software solutions for industry.