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…
Short circuit current contribution of a VFD Electric motors and generators contribute to the total fault level at the connection point. Their short circuit current is typically in the range 4…6-times the nominal current of the machine. How is the situation with a variable frequency drive? The answer is rather 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…
Protection of VFD transformers In the introduction to this series we have explained the differences between a distribution/power transformer and a VFD transformer [1]. Due to different design, construction and operation of VFD transformers the protection requirements shall be adapted as well. While many end users, system integrators, EPCs and Read more…