The NewElec MA motor protection relay provides a means of upgrading existing motor starters. It permits them to be controlled by Profibus DP, eliminating the need of having to replace older MCCs, before gaining the benefit of automating via the two-wire field control, fieldbus technology, of which Profibus DP is but one.
With the MA motor protection and control relay, this is achieved by providing programmable field I/O in the form of four relay outputs and five digital inputs with a wide voltage range of 24 V to 240 V a.c./d.c. The inputs can be configured as a common bus type input as in standard PLC applications, alternatively, the neutral of field supply for the MA's digital inputs can be connected to the existing auxiliary power supply neutral. Connecting a voltage signal to any of the digital inputs will be seen as an active signal.
The original control wiring remains intact with very little additional wiring being added, to link the MA closing and tripping relays into the closing and tripping circuits. The wiring from the MA digital inputs to the control interlocks needs to be monitored via the PLC or scada system.
Additional features such as actual load current, thermal capacity available in motor, alarm and trip flags for all fault conditions, running hours counter, time and date stamping of last four faults can be extracted via Profibus DP communications.
All configuration and parameterisation of the MA relay on Profibus DP is done using the PLC vendor configuration and parameterisation software. This incorporates the MA's GSD file into the vendor PLC device library to identify all the features of the MA relay to the specific PLC or scada system under Profibus DP.
The NewElec MA motor protection relay via an RS232 port running NewElec propriety free-issue software is able to record the three-phase currents, line voltage and phase voltage at 1 s intervals. The resultant text file is exported to Excel for analysis, with a typical file size of 7 MB for a 24 h period of recording. This feature has proved invaluable in monitoring load currents in mining equipment in flameproof enclosures allowing the identification of load related problems that have been plaguing the operation and engineering staff in the coal mining industry. Older P1 type laptops are ideally suited for the task, allowing one to find an economical solution to field measurement in harsh environments.
For more information contact Luc Dutrieux, NewElec, 012 327 1729, [email protected], www.newelec.co.za
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