EMC Aspect as Important Parameter of New Technologies

Equipment  disturbances  and  errors  have  become  more  serious  as  a  consequence  of  the growth of the electronic circuit complexity. According to new technical legislation and also economic  consequences,  the  electromagnetic  compatibility  (EMC)  concept  of  all  products must be strictly observed (Montrose & Nakauchi, 2004). It must start with the specification of  the  equipment  performance  and  end  with  the  equipment  installation  procedures.  The importance of the electromagnetic compatibility (EMC) of all electrical products has grown rapidly    during    the    last    decade.    The    environment    is    increasingly    polluted    with electromagnetic  energy.  The  interference  output  into  the  surroundings  is  doubled  every three years, and covers a large frequency range.

EMC couplings

The EMC concept is defined as competence of functional coexistence of electrical and also biological devices or systems at the same time and in such a way that even though they are located in the common electromagnetic environs, there is no relevant influencing factor of their normal functionality (Vaculíková & Vaculík, 1998). Devices can but don’t need to have the  mutual  dependence.  On  the  one  hand  the  systems  must  be  robust  against  the  other systems  influences,  but  on  the  other  hand  they  must  not  affect  adversely  the  normal functionality  of  other  devices  (Fig.  1).  On  one  side,  interferences  are  deliberately  or involuntarily produced. The place of their origin is called interference source. On the other side, devices can be hindered in their function by such interferences. Those objects are called interference objects.

From the viewpoint of the theoretical analysis it is evident that the radiated energy transfer between  individual  investigated  equipments  is  done  by  the  following  ways:  inductive coupling, capacitive coupling, galvanic coupling, electromagnetic coupling.

Inductive coupling

Inductive coupling is typical for two and more galvanically separated electric loops at the moment   when   the   smaller   one   is   driven   by   a   time   variable   current   creating   the corresponding   time-variable   magnetic   field   (Kůs,   2002).   In   such   case   their   mutual intercircuit effect is expressed as a function of the slope of the current increase or decrease, circuit environmental magnetic property as well as circuit geometric dimensions. To predict the intercircuit inductive coupling, our focus will be on two electric loops l1  and l2

with currents iand i2. We will try to determine the effect of loop lon loop l2  (Fig. 4).

Capacitive coupling

The capacitive coupling is typical for galvanically separated circuit nodes among which the mutual influence is represented by electric field strength  . Its distribution is given by the potential  at  the  particular  nodes,  geometry  of  the  system  and  dielectric  properties  of materials and media involved (Fig. 9).

Solution for the low frequencies and concentrated parameters

Minimum two or more electric circuits, which are mutually galvanically interconnected by one common conductor with its length l, represent a type of galvanic coupling. Due to low frequency operation it is possible to define the common conductor electrical parameters by concentrated parameters of its resistance and inductance L. If we suppose in the next step, that the conductor will be made of copper, so the voltage drop on its resistance will be much smaller in comparison with the voltage drop across its inductance L, which is caused by the time depending change of current. So, for the simplified analysis of the problem the conductor resistance will be neglected in the following. The schematic representation of the described problem is shown in the following figure Fig. 15. The mathematical description of the situation in the investigated circuit (Fig. 15. a) is then given  by  the  next  system  of  integral-differential  equations  (if  the  load  created  by  serial connection of R1L1  and Ccomponents is supposed):

By comparing the simulated and measured results one can find out that positive amplitudes reach approximately the same values 1.8 mV and similarly the negative amplitudes have the values 1 mV. The existing ripple and the absence of short positive voltage impulse with the amplitude  2.5  mV  inside  the  induced  voltage  course  obtained  by  simulation  is  caused  by considering only the first nine components of Fourier series. Generally it is possible to say that there exists a relatively great coincidence between the simulated and measured results. Thus  the  correctness  of  derived  equations  is  confirmed  as  well  as  the  fact  that  if  higher number  of  Fourier  series  components  are  used  the  better  coincidence of  both  type  results will  be  obtained.  It  means  that  during  the  electromagnetic  coupling  investigation,  as  one part of general EMC investigation, it is necessary to reconsider the compromise between the number of Fourier series components and the required calculation precision.The  above-mentioned  simulated  and  measured  results  are  sufficiently  identical  with  the theoretical results and so they confirm the correctness of derived equations. Such a way they can  be  used  for  predictive  stating  of  EMC  quality  of  individual  new  electrotechnical products (Williams, 2001).Based on the performed analysis also we can find out that the intensity of electromagnetic coupling is directly proportional to the amount and the time change slope of circuit current, which  is  radiating  the  electromagnetic  energy.  In  the  same  way  electromagnetic  coupling intensity depends on the length of this circuit. It is also directly proportional to the surface and  the  length  values  of  disturbed  circuit.  It  is  indirectly  proportional  to  the  distance between the interference source and the disturbed circuits, to the reflection coefficient and to the permeability and permittivity values of space between the both circuits.


The performed analysis enables constructers to improve the EMC parameters of the newly constructed devices not only by expensive testing measurements, but also in advance, by the theoretical analysis and simulation. They can state its supposed and required properties by a predictive method based upon the results introduced in this chapter (Kováčová et al., 2006). The improving of EMC will thus be more comfortable, cheaper, easier and quicker.

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