Beckhoff EL3773, Documentation

Page: 144 / 179

Commissioning
EL3773 144 Version: 2.5
Fig. 160: Overview of the performance of the calculations
Note
Calculation of the frequency and the sign of the reactive power Q
The frequency is calculated by determining the zero point of the zero crossing from positive
to negative. This time is constantly determined and compared with the previous zero cross-
ing.
The frequency is calculated from the time difference. The method used for frequency calcu-
lation serves only as a starting point for the determination of a possible algorithm.
It is up to the user to check the practical suitability of the method for a certain application.
Practical tests have shown that the frequency calculation of a very noisy signal with the
method used will not supply any reliable values. However, the calculation of the frequency
of the 50 Hz mains voltage worked reliably in the tests performed.
The same applies to the determination of the sign of the reactive power Q, because this is
determined by comparing the times of the zero crossings of the voltage and current.
6.11.4 Starting the example program
The application examples have been tested with a test configuration and are described accordingly. The
program serves as an initial introduction to the options for evaluating the data from a mains monitoring
terminal. The user is free to change the program to suit his ideas or to use only part of the code.
• The following hardware and software were used for the test configuration:
TwinCAT Master PC with Windows XP Professional SP 3 as operating system, TwinCAT version 2.11
(Build 2230) and Intel PCI Ethernet adapter
• Beckhoff EK1100 EtherCAT coupler, EL3773 and EL9011 terminals