AC DRIVES vs DC DRIVES

AC Drive - Variable Frequency Drives (VFD) and AC (alternating current) motors are not new to the industries. They have been around for many years. The VFD’s were just too expensive to use in smaller application and too complex. The best part about using a VFD was that you could keep the AC motor that was already being used in the application. So for many years all that was used on machines that needed to adjust the speed of a motor was DC (direct current) motor drives and DC motors. The cost of a VFD used to cost more than a DC motor and a DC motor drive together.

Now with all the new technologies that have been developed over the years the manufactures are able to be more competitive with the makers of the DC motors and drives. With the cost of a VFD and a DC motor drive at almost equal cost and the cost of a DC motor at almost double the cost of an AC motor. It only makes sense to replace the DC motor drive and DC motor with a VDF and an AC motor.

There are also many other considerations as well. If you already have a machine that has an AC motor and you would like to vary the speed. Like if you had a conveyor that was running to fast. All you would have to do is install a new VFD. Then you would be able to adjust the speed of the motor which in turn would adjust the speed of the conveyor or any other equipment that the motor was being used for.

DC motors were also known for the higher maintenance and repairs that was required to keep them running. Like replacing motor brushed, cleaning the commutator, and cleaning out the Carbon that would build up just to name a few. AC motors are very maintenance free and extremely reliable.

DC drive also had problems. When a DC motor would burn out it would also in many cases burn out the DC drive. With a VFD there are many protections to keep this from happening. There are also many protecting features in the VFD to keep the AC motor from being damaged.

VFD’s also have gone through many changes over the years. One of the best changes is that they are much more user friendly. Most of the VFD’s on the market today have an operator interface for programming and making changes to the setting on the fly and a display that uses plain text that makes it easier to understand.

Manufactures have also taken many extra steps to help in designing newer electronic circuits that increase the efficiency of the AC motors that they control. This motor efficiency means that it will cost less to operate. There are also many special filters that are used in the VFD’s to produce a cleaner power source to the motor that can also help to increase the life of the motor.

Looking at the big picture at this time it only makes perfect sense to build newer equipment or replace existing DC drives and DC motors with VFD's and AC motors not only for the reliability but also for the efficiency and the cost saving on maintenance and energy consumption.

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