![]() ![]() Or, as Michael calls them, his best friends in the whole world, because as far as he’s concerned, there’s not really a difference. Of course, he did so by being the least socially aware human ever to grace the small screen, making life absolute hell for his employees and underlings at Dunder Mifflin. To many viewers watching The Office, Michael Scott achieved that status many times over, with fans of the show laughing uproariously almost every time he opened his mouth. On the other hand it is a clearly defined system with well known machine parameters making it easier to manage.For seven years, Steve Carell treated TV audiences around the world to a truly unique character, who proudly stated his goal of making everyone afraid of how much they loved him. On one hand there is the variable output frequency. However, machine side has somewhat different aspects. On the machine side there is practically always some kind of filter (as minimum a dv/dt filter reducing the voltage slope and ensuring compatibility within the inverter-cable-motor system ). However, it is rather challenging to make a filter design that is robust and stable during grid faults and other unusual operation states. The purpose of a filter is to absorb specific harmonics and eventually compensate the reactive power. Since the grid parameters are project-specific a grid filter is usually an engineered solution. This applies mainly for the grid side filter. If possible, a filterless VFD design is preferred. Of course, there are high performance applications that require speed and/or position encoder. In sensorless variant the speed is calculated in VFD software based on electrical signals that are already available. unbalance), environmental factors (dust, vibration) etc. Performance of an encoder is affected by multiple factors such as physical distance between inverter and motor, type of signal, interfences with other equipment (EMC topic), installation aspects (e.g. Sensorless speed controlĮlimination of a speed encoder can also be seen as a step towards KISS. It reduces the parts count, simplifies the maintenance job throughout the lifetime of equipment and boosts the availability. A fuseless design will be more in line with KISS principles. In the example of a 5 MW, 4.16 kV multi-cell inverter a total amount of 36 fuses is needed (some manufacturers reduce the quantity to 24 pcs using two fuses per cell). And again, there is the topic of quantity. ![]() Fuses also naturally age making the maintenance somewhat cumbersome. The fuse needs to have very quick response to provide required protection of semiconductor devices. ![]() Use of fuses in medium voltage VFDs is tricky. Thus increasing the probability of leakages. ![]() Inverter with high quantity of semiconductors also requires large quantity of plastic pipes distributing the water to the individual heat sinks. Similar situation is for example with cooling pipes in case of a liquid cooled VFD.
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