Hi, i am going to select a MV VFD for fan. I am going through all the vendors brochures , however, what are the points i should check thoroughly to avoid VFD failure? also, we are buying motor which will run both on VFD and DOL starting .any special requirement i should check on apart from insulation?
thanks in advance .

Perhaps the reason no one has replied to your inquiry— is that your questions are much too broad.
Kind of like calling up your local hospital and telling them that you are going to remove your girlfriend's appendix and would like them to tell you all the things you must know in advance.

I think you will find that the forum will respond to you if you narrow the scope of your questions and provide as much detail as you can.

In this case you have provided no information other than its a fan application and that just isn't sufficient information to understand your application and the details thereof.

So, in a very broad and general sense, consider that you usually get what you pay for and so, if you purchase a low-end VFD as opposed to a high-end VFD, you can usually expect the life to be a consequence of your decision.. High-end equipment tends to have higher quality and reliability; low-end products are at the opposite end of the quality/reliability spectrum. That being said, I have seen high-end products destroyed by subjecting them to installation and application factors that eclipse their design capabilities.

With regard to the selection of the motor for your application, your question should be directed to the motor manufacturer to assist you in making a correct selection for your application.

Kind regards,
jΩ