Existing and prospective customers often ask "What is the purpose of the digital inputs/outputs on NewElec's MA motor protection relay?" Those asking are generally speaking from a non-automated applications viewpoint and are considering standalone applications.
The NewElec MA range has five digital inputs, which accommodate an external field supply voltage of between 24 to 220 V a.c or d.c. The motor protection relay is also equipped with four output relays. Two of these are programmable in that they may be associated to the digital inputs mentioned above. The moment a potential is applied to any of the digital inputs it becomes 'high' or switches 'on' (1). If the potential is removed it becomes 'low' or switches 'off' (0).
It is now easily understood how these digital inputs can be used in standalone applications for extended control of processes since we can now, by example, use the following logic: If digital input X goes 'high', output relay Y must energise (the pilot circuit is healthy). Relay Y in this example would be interlocked into the start circuit so that it would only be possible to start the given motor providing the pilot circuit was healthy. Now consider that the motor protection relay includes solid-state timers for both programmable output relays so that the logic may be further advanced to permit more flexibility. Lastly, the relay logic may be configured to follow the programmed instructions only if the motor is in service or only if the motor is out of service.
See below for some previously satisfactory solutions that NewElec's customers have used to meet their requirements on site:
* Sequential starting of conveyor belts with timed intervals.
* Automatic starting of a standby pump when the primary unit fails.
* Four logical input (1, 2, 3 and 4) conditional start.
* Pre-warning alarm prior to start.
* Forced running of ventilation fan underground before starting other motors.
The NewElec MA protection and control relay is issued with free standalone software that also provides an easy I/O allocation truth table to facilitate the programming of the relay.
The NewElec MA relay supports all popular communications protocols and has an excellent platform of standard integrated protection benefits that include earth leakage and voltage protection features. It is also very flexible on the digital input field supply side, and the enterprising engineer will realise how he is able to automate his old plant immediately at a very economical price.
For more information contact Luk Dutrieux, NewElec, 012 327 1729, [email protected]
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