Power and Air Minimum Requirements

    

                     8 pages,  4 MB



Minimum requirements for Power                                                

All of the Electronic Inspectors, whatever the:

  • amount of the CPUs on which they are based;
  • linear speed of the containers whose physical properties they are controlling;
  • number of containers they have to check each one second;

are measurement systems processing signals of high-frequency, short-duration and small amplitude. Measurement systems lying in an industrial ambient where motors and frequency converters creates spikes and other signals of high-frequency and short-duration.  These signals are superimposed, mainly due to induction, to the true signals outcoming by the Electronic Inspectors' sensors translating themselves also in jitters of the signals processed by the CPUs.


 Electronic Inspectors have to be powered in a specially conditioned way.  Strict limits are imposed to the harmonic content of the sinusoidal function.  Total harmonic distortion introduced by the sum of 2nd to 5th harmonic oscillations has to be ≤ 10 % and the total of the 6th to 30th harmonic oscillations has to be ≤ 2 %










When there is to power something like this, the common rules valid for Programmable Logic Computers power are no more valid. Because of such criticities, the Author of this notes had been compelled tens of times to apply to the mains a 50 MHz bandwidth digital Oscilloscope.   

One freezing into its memory of 48 consecutive hours all and each one of the:

  • spikes with peak value until 860 V, superimposed to what had been considered until that moment to be a fully compliant 380 V mains to the Electronic Inspector;
  • voltage cut-offs, until 100 ms;
  • voltage drops, until 50 % of the peak voltage. 


Food and Beverage companies in the entire tropical and semitropical band of the planet, know how many negative consequences arise by the named “electric storms”.  They have been measured lightnings' potentials > 3.5 billion volts. Transient over voltages are just one of the many dagnine effects affecting the Bottling Controls electronics 









Some of the common values specified by several Vendors of Food and Beverage Machinery and controls, as minimum requirements for their Programmable Logic Controllers (PLCs) and Electronic Inspectors’ power, can be synthesized as: 

Deviations of the voltage

  • Nominal voltage of 115 V:                                             ± 10 % nominal voltage
  • Nominal voltage of 230 V (400 V):                                 ± 10 % nominal voltage
  • Nominal voltage of 240 V (415 V):                                 + 6 %, -10 % nominal voltage

Deviations of the frequency

  • Permanent:                                                                    ± 1 % of the rated frequency
  • Temporary:                                                                    ± 2 % of the rated frequency











 Fourier Theorem is not only relevant in Optoelectronics because of the Fast Fourier Transform applied to the convolution of images.  Also, it indicates the way to correctly power whatever Electronic Inspector, in terms of harmonic oscillations.  In the formulas above, for integers N ≥ 0, the summations sN(x) are periodic with period P,  where aN  and  bN  are the Fourier coefficients. To these harmonic oscillations, until the 30th, we are referring in the text above, as something which can truly affect the future of the Bottling Line, preventing correct function of the Inspectors.  Designers engaged in the power distribution to a new project of Bottling Line, to prevent future problems of kinds whose diagnosis is not banal, have to care a pre-analysis of the Line and choose, after tests, what mono phasic line to connect to the Inspectors 






The wave form of the power ideally should have to has to be  sinusoidal.                                                                           

Harmonic oscillations and total harmonic distortion:

  • Total of 2nd to  5th  harmonic oscillations:               ≤ 10 %
  • Total of 6th to 30th harmonic oscillations:                 ≤ 2 %

Voltage interruptions:                                                         < 3 ms   (≤ 1/second)

Voltage drops:                                                                    20 % peak voltage for ≤1 period

                                                                                            (≤ 1/second)





When it is known not to be possible to fulfill one of them, it is mandatory to introduce an UPS.    

Nearly all Electronic Inspectors are monophasic.  Because of this reason, it is suggested to study the power distribution to the motors of the Bottling Line, to choose the most balanced single phase for the Inspector's mains.    









Minimum requirements for compressed Air


The solenoid valves used in the rejectors of the Electronic Inspectors are expensive models, in between the fastest existing in the World, easily and permanently damaged after receiving eventual material residuals flowing thru the piping, oil or water. A valve made defective by these factors can introduce a permanent and hidden disturbance to the Production, e.g. by mean of irregular movements of the Rejector cylinder it controls.

More, the air is used to cool sensible CCD-cameras in optics’ cabinets. Because of these reasons, it is really important to take care of the air quality.

Following the Norm ISO-DIN 8573-1 'instrument quality', the air has to be clean, dry and oil-free, say:

  • solids content quality:                                                  category 2
  • pressure dew point quality:                                          category 4
  • max. oil content quality:                                               category 1


To reject means also to accomplish an action with minimum possibility for delays.  The air infeeding the valves has to be particularly cared.   As can be seen by one of the figures down, when powered at 24 VDC, the solenoid valves response times is reduced to 2 ms when de-energising and to 6 ms when energising.  It is exactly because these times are so small that these calves can be used in an Electronic Inspector.   

It is vital to prevent their progressive degeneration, induced by water, oil and other impurities travelling thru the piping.



 

 















What gets out of the air filter immediately before the solenoid valves visible in the images down, when draining each ~ 6 hours, in an Aseptic Filling Bottling Line.  In these conditions, hinting to a missing or non-functioning air dryer which must have been active in the outfeed of the Bottling Line Main Air Compressor, also the lifetime of the best solenoid valves existing in the World is deemed to values close to the poorest & low quality models














  A battery of MAC® solenoid valves and cylinders in a multi segment rejector







 MAC® solenoid valves specification for one of their series frequently adopted into Electronic Inspectors and other Bottling Line Machinery.  In evidence, when powered at 24 VDC, the response times of 2 ms when de-energising and 6 ms when energising.   To prevent degeneration of these values, the air infeeding the valves has to be cared much more than what necessary for all other Machines and Devices composing a Bottling Line



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