New electronic motor-protection relays help to enhance energy efficiency

Designed to help engineers cut stock management costs and simplify design processes whilst ensuring high reliability according to international standards, a new series of highly-versatile and efficient electronic motor protection relays has been introduced by WEG. The RW_E relays offer a wider adjustment range to suit a broad spectrum of motor powers and deliver 87% less power dissipation than conventional thermal devices, therefore providing enhanced energy efficiency, while ensuring the motor’s smooth running and enabling users to reduce maintenance costs and total cost of ownership. The RW_E relays’ wide current adjustment range of 1:5 ratio between the lowest and highest settings allows the relays to cover an extensive variety of motor powers at rated operating voltages up to 690VAC. This enables original equipment manufacturers to reduce their stock of spare parts and associated warehousing costs and invest less time in designing machinery to accommodate different relay models, says the company. “In an increasingly globalized and competitive market it is common that machine manufacturers provide their customers with a wide choice of electric motors with a huge number of different models and output powers,” said Marek Lukaszczyk, European and Middle East marketing manager, WEG. “WEG’s solution means that machine manufacturers can now standardise their control panels, saving time.” The new relays have ratings from 0.4A to 840A and protect electric motors for normal or heavy-load starting against overheating due to overload, phase drop-out or phase asymmetry. Powered by the motor’s current without any need for additional external power connections, the RW_E relays feature special thermal memory which precisely models the heat balance of the motor to ensure optimal protection. The low power dissipation also makes a significant contribution to reducing heat load in switch cabinets and enables the replacement of corresponding equipment in switchgear sets approved to IEC 61439 without new certification. The relays are just as easy to use as bimetallic motor protection relays, and feature manual or automatic reset after tripping. Trip classes 10, 20 and 30 for normal and heavy-load starting can be set easily on the front panel. This makes the RW_E motor protection relays suitable for a wide range of industrial applications and enables users to respond flexibly to changes in existing systems. The relays also include temperature compensation, which ensures consistently high trip accuracy from -20C to +60C with no restrictions. The relays provide the highest levels of reliability worldwide and are manufactured and tested to the IEC/EN 60947 international standard (DIN VDE 0660) and UL 60947-4-1A (UL508) certification for the North American market. The RW_E electronic motor protection relays can be combined directly with WEG's CWM and CWB contactors to configure compact and reliable motor starter sets. “These new relays fit our strategy of end-to-end energy efficiency throughout the drive chain, starting with energy-efficient IE3 to IE5 motors and extending to thermal protection by RW…E electronic relays, short-circuit protection by MPWi circuit breakers, and operational switching by low-loss CWB contactors,” concluded Marek.