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R&D focus leads to improved motor protection offering

24th May 2013

By: Ilan Solomons

Creamer Media Staff Writer

  

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Motor protection company NewElec says it has made significant upgrades to its range of motor-protection relays in the past three years, which the company attributes to rigorous research and development (R&D) processes on which it spends several million rands each year.

“The company examines its range of protection relays daily to find ways of improving its offerings,” NewElec sales manager Luc Dutrieux tells Engineering News.

NewElec’s design team is headed up by SD Loudon, who is assisted by computer-aided design software and software development personnel.

Dutrieux explains that, in the past ten years, the R&D of protection relays has emphasised the communication and control aspect of motors, including the management of motors using programmable logic controller communication protocols.

The development of software systems to support the communication platforms of the design process, including independent testing, both locally and internationally, has also been undertaken to ensure compliance with industry protocols.

“Designing a protection relay, manufacturing a prototype and then testing it to produce the final product can take six months to five years, depending on the relay type and whether the company is designing a product from scratch or simply making alterations to an existing product,” explains Dutrieux.

NewElec’s products are all thoroughly tested in its laboratories for a minimum of three months, which includes radio interference testing, before being launched onto the market.

MA Series

Dutrieux notes that the MA Series of motor-protection relays was first launched in South Africa in 1999 and was upgraded during the past two years. It was initially bought by JSE-listed group Exxaro Resources for use at its Grootegeluk mine, in Limpopo. The series has had eight software revisions to date and continues to be a prime seller for NewElec.

Dutrieux says, although underload con-ditions can never be eliminated entirely, the MA Series motor-protection relays prevent mechanical failure of pumps and other unfavourable conditions, such as short circuits between turns and winding failures.
“All the company’s motor-protection products use the same concept with regard to the manner in which currents to the motors are monitored. “All relays use current transformers that are connected to each phase and, as a result, determine the loads drawn by the motor protection,” he explains.

Dutrieux adds that the current transformers may, at times, be an integrated relay component or separately mounted and fed back to the protection relay. This permits the relay to register the starting in-rush current and determine whether the motor is accelerating, under load, or whether there are unbalanced loads in the phase current.

“The MA relay range can also monitor phase voltage, therefore, allowing additional voltage-monitoring protection features. It also has integrated current transformers on board and earth-leakage protection,” says Dutrieux, adding that the integration simplifies installation and reduces the mounting space requirements.

Besides the maximum load, one of the user inputs for protection relays is the thermal curve class that equates to the safe, cold stall time of the protected motor.

While a motor is running, the protection relay monitor, whether it is operating above or below the selected current limit, increases the motor-modelled temperature during an overload, and decreases it when the motor is not loaded.

KD and KE Range

“The KD and KE ranges of low-voltage three-phase motor-protection relays, which were launched in 2007, are designed for conveyor, compressor, crusher, fan and pump-motor protection,” says Dutrieux.

He explains that the KD relay facilitates certain control-panel-mounted settings, while the paramatisation of the KE is fully software driven.

The relays are simple to set up using a man-to-machine interface or a computer using the company-supplied, free setup software. A range of protection features is offered, including thermal overload, earth-insulation lockout, earth leakage and short-circuit protection.

“The KD and KE motor protection relays are also equipped with an integrated current transformer that allows direct measurement from 0.1 A to 50 A. External-current transformers can be used to extend the current range to meet a customer’s requirements. Power measurements monitor real-time power consumption and power consumption over extended periods,” says Dutrieux, adding that all features and information can be accessed through an external Profibus communication unit.

The relays initiate programmable starts every hour, enable permissible consecutive starts and record 2 000 uploadable time- and date-stamped events. Further, they record the last 60 faults, pertaining to current and voltage values, with complete details and have software-based real-time recording capabilities to aid motor management.
“The relays are also equipped with a simulator that enables trainee electricians to experience the relay settings and simulate test faults of their own,” notes Dutrieux.

Edited by Tracy Hancock
Creamer Media Contributing Editor

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