Posts related to protection of variable speed drive systems.
What types of electromechanical switching devices are used in MV VFD systems? In this blog post we will talk about switches in variable frequency drive (VFD) systems. However, our subject are not the semiconductor switches but electromechanical switching devices (e.g. circuit breakers). Classification of electromechanical switches We will start with Read more
How to consider explosion load of a transformer? Abstract When oil filled transformer is installed indoors, the explosion load becomes relevant for the building design. Introduction In a common setup, dry type transformers are installed indoors while oil-filled transformers stand outdoors. Dry transformer can be located outdoors as well if Read more
VFD protection reaction Reliable protection is key for long term successful operation of a variable frequency drive (VFD). There is a wide range of situations outside of the normal operation to what the drive system shall respond. In this blog post we briefly explore the VFD protection reaction. Introduction VFD Read more
Fault current considerations for integrated transformer of CHB drive Introduction Cascaded H-bridge (CHB) variable frequency drives (VFD) have the input transformer as an integral part of the VFD. This transformer has high number of secondary windings (equal to the number of VFD power cells). Such multi-winding transformer represents a challenge Read more
Fuseless is not useless This post addresses the VFD protection concept and particularly the concept eliminating medium voltage fuses – so called fuseless design. We explain the advantages of such approach and why it is definitely not a useless feature. Concept of fuseless design Solid protection concept is key point Read more
What do the protection function numbers mean? In single line diagrams and other documents depicting protection details you can see various numbers. These numbers are also called ‘ANSI codes’ as they are defined in the ANSI/IEEE standard. What do the protection function numbers mean? You have surely seen them: the Read more
What makes protection firing so brilliant? Protection firing, sometimes also called “firing through”, is a VFD protectionconcept used in some medium voltage drives. The principle is well described in its name:In case of a severe fault the VFD will turn on all the active switches (such as power semiconductors in Read more
How to calculate the short circuit current in a correct way? Calculation of short circuit current is essential for the design, dimensioning and protection of electric systems. Such system may be for example a substation, a transmission line, a generator or a variable speed drive system. In fact, the calculation Read more
Protection of VFD-fed motors How to properly protect an inverter-duty variable-speed electric motor? What protection is covered by the VFD? What shall be done externally? Which protection elements are most suitable? The article on protection of VFD-fed motors brings the answers. General considerations System and equipment protection is of crucial Read more
Short circuit currents appearing in variable speed drive systems The knowledge of short circuit current level in variable speed drive systems is crucial for the design of system components as well as for the system protection. Inadequate dimensioning, unsuitable protection concept or wrong parameterization may lead to fatal consequences: Hazard Read more