How to choose a medium voltage VFD (Part 1: Introduction) We start a new series dedicated to the selection of medium voltage variable frequency drive. Some points might also be valid for low voltage VFDs. However, many topics require different considerations in medium voltage range compared to low voltage. Purchasing Read more
Reliability and availability (Part 4: IGCT based converters) IGCT is a power semiconductor used in medium voltage converter applications. The abbreviation stands for Integrated gate-commutated thyristor. Unlike classical thyristor that can only be switched on, IGCT can be switched on and off through its adjacent gate unit. Therefore, it is Read more
Reliability and availability (Part 3: Semiconductor redundancy) Today we gonna talk about N+1 semiconductor redundancy. When is it needed? What are the benefits and drawbacks? The main purpose of redundancy is to increase reliability and availaibility of a system. Therefore, to answer if N+1 semiconductor redundancy is needed, we shall Read more
Project specificationsToo little / too much? In this post we talk about balancing the length and especially the content of project specifications. What is too little and what is too much? How to specify your requirements? Let us spend some thoughts on this subject. Balancing the project specifications Specifications are Read more
#LCI versus VSIPart 2: Truth and lies about LCI and VSI We continue our series about the high power drive champions LCI and VSI. The introduction [1] last time was a bit longer, but the goal was to provide a good and unbiased overview. There is quite some material regarding Read more
LCI versus VSIPart 1: Introduction LCI (load-commutated inverter) and VSI (voltage source inverter) are the dominant technologies when it comes to high power medium voltage drives. Each technology has certain advantages as well as drawbacks. Project specific conditions and requirements shall be analyzed before deciding for LCI or VSI. Let’s Read more
#Energy efficiencyPart 3: Selection of VFD technology What type of VFD technology fits the best your demands? The answer depends mainly on your process and operation philosophy. Process dynamics Is your process very dynamic and fast response is required? Then you will need a high performance drive that can track Read more
#Energy efficiency Part 2: Applications with energy saving potential What applications can benefit from variable frequency control the most? To help understand it we use some fundamental equations (don’t worry, there will be no high mathematics!). Mechanical power Pmech is the product of torque T and angular velocity w. The Read more
Reliability and availability (Part 2: MTBF) Let’s start with the mystery around MTBF (Mean Time Between Failures). You may disagree with me, but please give me a chance and read to the end before you make your mind. Many people believe that the higher MTBF figure the more reliable system Read more
Reliability and availability (Part 1: Introduction) Reliability and availability are crucial characteristics of drive systems and every downtime negatively impacts the productivity and profitability of a plant. In this series we would like to walk through the topic, provide some (theoretical) background and also a more practical approach. We have Read more