When it comes to selecting a VFD for a motor, many professionals start with the values provided for Normal Duty (ND) and Heavy Duty (HD). It seems straightforward \u2014 these ratings supposedly help match a drive to a motor based on its operating cycle. But here’s the truth: these numbers can be misleading. In fact, the Heavy Duty rating is essentially a derated version of the VFD’s Normal Duty value.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t VFDs usually come with two sets of ratings: one for ND and one for HD.<\/p> Now, here\u2019s the trick: these ratings aren\u2019t as independent as they may seem. The Heavy Duty number is simply a reduced version of the Normal Duty rating. So, a VFD rated for 30 kW in Normal Duty could only handle 22 kW in Heavy Duty. What\u2019s important to understand is that these two numbers don\u2019t represent different capabilities \u2014 HD is just the drive operating in a more restrictive condition.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\tBreaking Down Normal Duty and Heavy Duty Ratings<\/h3>
Why Current Is More Important Than Motor Power Rating<\/h3>