Monitoring relays increase plant availability

Paul Boughton

Siemens Automation and Drives' new Sirius 3UG4 series monitoring relays can be used to protect critical plant and machinery

Three new Sirius 3UG4 series monitoring relays are being launched by Siemens Automation and Drives (A&D). The devices are available in versions for single-phase voltage monitoring, single-phase current monitoring, as well as monitoring of cos phi and active current on motors.

In this way, Siemens claims the products can increase the availability of machines and equipment. The relays have a switchable fault memory and can detect violation of the digitally adjustable upper and lower limit values. The display constantly indicates the actual value and the type of fault, and, thanks to the wide voltage range, it can be used worldwide.

The device version for cos phi and active current monitoring is suitable for running motors well below the rated torque, as in no-load operation of a pump, for example. Active current measurement and monitoring for violation of upper and lower limits facilitate advance maintenance information, so plant availability can be increased. It is possible to choose between the cos phi and active current measuring principles.

For more information, visit


Recent Issues