Electrical Power & Protection


Zest WEG Group’s protection systems

December 2015 Electrical Power & Protection

The continuous pursuit for improvement and cost reduction in industry has seen a rapid evolution in the development of electric motor control and protection systems. “To ensure that we meet all the needs of industry in this regard, as well as keeping abreast of the latest trends and developments, the Zest WEG Group has introduced its range of RW_E electronic motor protection overload relays, to complement the range of smart relays,” says switchgear manager Stephen Cook.

The relays are designed for increased reliability in terms of the protection of low-voltage three-phase motors in sinusoidal 50/60 Hz networks where reliability, low power dissipation and ease of maintenance are critical requirements. They have been developed in accordance with the IEC 60947-4-1 and UL 60947-4-1A (UL 508) international standards.

RW_E Electronic overload relays are highly reliable devices intended to protect motors, controllers and branch circuit conductors against phase failures and overloads that can result in overheating. These critical products play a vital role in overall system performance and efficiency and are designed to protect three-phase and single-phase AC motors.

The electronic overload relay has no power contacts and therefore cannot disconnect the motor by itself. Instead, motor overloads or phase failures increase the motor current, which in turn trips the mechanism and switches the auxiliary contacts. When wired properly in series with the coil of the contactor, these auxiliary contacts will de-energise the contactor in the event of an overload.

This means the contactor itself disconnects the power supply to the motor, halting its operation. Another handy feature is that, once tripped, the relay will only reset once the motor has cooled down, preventing costly damage. The relays are also temperature compensated, which means that the trip point is not affected by temperature and it performs consistently at the same current value.

In order to ensure rapid tripping in the case of phase loss, and thereby protecting the motor and avoiding costly repairs or additional maintenance, the WEG RW_E relays include phase failure sensitivity protection as a standard feature. They can be mounted directly onto the WEG CWB and CWM contactor ranges, which make for highly reliable and flexible motor starting units.

For more information contact Kirsten Larkan, Zest WEG Group, +27 (0)11 723 6000, kirstenl@zest.co.za, www.zest.co.za



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