The safe switching of three-phase asynchronous motors for machines not only requires the selection of the correct switching devices. The cable to the load also has to be adapted to the ambient conditions to carry the current safely in all situations. Some calculations are required to find the suitable cable cross-section and ensure it is the right one.
The switching and protection devices required to operate the motor depended on the mechanical load and until now had to be determined with reference to the SIRIUS Configuration Manual or by searching the catalog. This was followed by a search for suitable variants with the correct control supply voltage and type of connection, and the necessary auxiliary contacts.
This can now be done more easily, as you can find the right switching and protection devices for your motor quickly and easily using the Load Feeder Configurator+ (IEC).
Many constraints have to be taken into account when determining the cable cross-section. These include the ambient temperatures, method of installation and number of loaded circuits or cables. The cable also has to carry the current safely under overload and short-circuit conditions. Furthermore, the voltage drop must not be too large and the minimum short-circuit current not too small so that the motor can be safely switched and also safely shut down in the event of a malfunction.
Finally, the standard IEC 60204-1 specifies the minimum requirements for electrical safety for the protection of the machine, drives, and operator. However, additional standards such as IEC 60364, IEC 61439, IEC 60909 (short-circuit calculations) or VDE 100 also have to be consulted frequently.
The cable cross-section is determined in the Load Feeder Configurator + (IEC) at the press of a button. Parameters such as the method of installation, bundling and ambient temperatures can be selected freely to dimension the cable as optimally as possible for the prevailing conditions.
Yes, since a short circuit can occur in any system and the installed devices must safely switch off the short circuit, the need for a short circuit calculation already results from the risk assessment, which is mandatory according to the European Low Voltage Directive. Furthermore, the current version of DIN EN 60204-1 - Electrical Equipment of Machines, published in October 2016, requires that the rated short-circuit current of the electrical equipment must be determined.
By the way: The Load Feeder Configurator + (IEC) determines the relevant short-circuit values automatically.
You will find the Load Feeder Configurator + (IEC) in the offline version of the TIA Selection Tool under the topic "Industrial Controls". Download the TIA Selection Tool for this purpose. Do you need a step-by-step guide to obtaining the feeder configurator+ (IEC)? If so, then watch our tutorial.
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