As VFDs have evolved over the years, new unique challenges have presented themselves to those who are specifying and designing them along with the motors they are controlling. These challenges have come about for a variety of reasons.
First, the motors being controlled years ago were overdesigned and less efficient than those we have today. VFDs did not have the technology to control as much so the motors had to be engineered more precisely and effectively. Because they were so overdesigned, the older motors were actually less prone to failure than today’s more efficient motors. Additionally, current VFDs have become smaller. Due to this reduction in size, there is less filtering applied inside of the drive due to costs and space constraints. There is a large propensity for rooftop mounting equipment, and VFDs are being placed farther away from the motors they’re controlling. Furthermore, when VFD technology was first introduced, it was much slower, especially when compared to the current Insulated Gate Bipolar Transistor (IGBT) technology engineers are familiar with today. This added speed can have an adverse effect on the longevity of the VFD controlled motor if not handled properly.