As with anything, there is an old saying, “You get what you pay for.” In many cases, variable frequency drives (VFD’s) have come down in price, but then again, it all depends on the application. For instance, using the 7.5 HP theory,
I would not use a drive that does not have the option to run in closed loop sensor vector mode for an extruder. I would however, use that type of drive in a pump or blower fan application, where speed deviation is not that critical. With VFD’s that use sensorless vector and sensored vector, speed control is of a higher tolerance, which in turn will cost you more money.
New VFD’s are incredibly efficient and able to deliver full torque throughout the entire specified RPM range of the motor being driven. I’ve been in the industry for nearly 15 years and have always sized the drive accordingly to the motor size and have never had any problems. Repair Zone considers Allen Bradley to be near the top in quality, and when you want all the bells and whistles, the Powerflex 700 series can pretty much accommodate anything, where in the 7.5 HP range you will typically spend just over $2,000.00. Now, on the other side of the spectrum, you could pick up a Hitachi 7.5 VFD (which is still a quality drive, just with less options) for roughly $600.00. Just keep in mind; it all depends on the application.
Repair Zone efficiently and cost effectively repairs Allen Bradley drives, including Powerflex 700 series, compared to buying new.
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