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vvvf inverter for elevator Soft starter or variable-frequenc

Author:Elevator Inverter Time:2021-04-20 14:38:52Click:
vvvf inverter for elevator Can you talk about the pluses and minuses of using a soft starter or an ac variable-frequency drive (VFD), as well as explaining the applications in which one might be a better fit than the other?
Greg Maryniarczyk thumbGreg Maryniarczyk, test engineer at DLS Electronic Systems:
Soft-start drives are used to limit inrush current associated with electric motor startup. Soft-start drives lower the initial voltage by adding solid-state series impedance and ramp up until full speed is achieved. Doing this extends the life of the motor and mechanical components that are connected to it. Large motor electric inrush current also places a high demand on the electrical supply system, which often results in extra cost.
VFDs deliver much higher frequency source power during startup to reduce current due to the increased inductive impedance. This can be advantageous if control is desired after full speed is reached. This control allows for continuing control as the load on the motor is changing. VFDs are more efficient and produce less heat, while being able to start motors under considerable loads. In both methods, as the motor reaches operating speeds, the counter electromotive force (CEMF) increases to limit current to steady-state conditions.

A decade ago, a group of young Singaporean designers, friends who returned to their homeland around the same time after working abroad, decided to go into business together as Stuck Design. The venture, ahem, stuck, and now, the 28-person team led by Tze Lee, Yong Jieyu, and Donn Koh has completed an array of multidisciplinary projects, including pandemic-ready technologies to mitigate COVID-19. One in particular is Kinetic Touchless, an elevator-button device that automatically depresses when it senses a finger hovering before it. “In contactless interfaces, we often use sound and light for input,” Koh says. “But we tend to forget that physical movement is a satisfying form of haptic feedback.” And the product isn’t limited to just elevators: A sliding door could follow the move­ment of your hand 2 inches away

The mechanical details of Kinetic Touchless. Photography courtesy of Stuck Design.

Photography courtesy of Stuck Design.

All the talk about returning to work in the office has dialed up my anxiety. I’ve been lucky enough that I could work remotely for the past year, unlike frontline workers. But now I can’t imagine taking the subway to my office. My stomach seizes up when I picture myself before an elevator with two or three strangers already standing inside, waiting for me to step in. I look forward to seeing my colleagues, but I also worry that everyone else will adapt to this next phase of the pandemic quickly, while I’ll still be paralyzed by fear.

Sian Beilock, the president of Barnard College in New York and a cognitive scientist, has some comforting words for people like me: The dread I’m feeling right now may be the height of my anxiety. Her research has shown that when people are worried about something, “it’s the time right before it happens, where you see most of the anxiety play out,” she says. This was confirmed by a study that tracked subjects’ brain changes when they were told they were going to have to take a math test. “We just tell them the math is coming, [and] that’s when we see areas of the brain that are involved in anxiety and pain being activated,”