While variable speed drive (VSD), also called variable frequency drive (VFD), is a cost-effective solution for many applications, it is not a cure for all motor problems. This is the biggest misconception in the industry that you need to know the truth behind it. There are many cases when VSD overloading that does not properly set up the motor windings results in overheating. This often results in permanent damage. This is why it’s crucial to choose the right VFD for your specific application.
First, when you are specifying the rated torque output of the motor, you have to consider the required speed range and the amount of overload that you encounter when starting the drive or at any other steps during the operation. Also, you have to consider that the motor has compatible thermal properties with that of the drive you choose.
Moreover, if you are working with a Class F winding insulation, you might need to ensure that the incremental encoder is factory fitted to the shaft’s non-drive end and that the output communicates with your variable speed drive. This is popularly referred to as the closed loop control that gives excellent motor speed holding despite sudden changes in the torque load.
Finally, once you have selected the motor, you can then pick the right VFD that can go with it based on its rated current, frequency, and voltage. One of the most important parameters that can affect your VSD selection is the ambient temperature. This means if the drive will be installed or operated in a closed-loop environment, it should come with enough ventilation with multi-channel encoder inputs. However, when you are going to use it in harsh working conditions like the ones you found in logging and quarrying, it is more advisable to use sensor less control.
So, as you can see, picking the right variable speed drive is not a straightforward task. You have to consider the above conditions first to make sure that you invested in the right equipment.
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