New electronic motor-protection relays help to enhance energy efficiency

17-06-2015 | Weg Electronics | Connectors, Switches & EMECH

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

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

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

“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.

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