AC or DC Drive-Which is Best for Small Motors?

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AC Or DC Drive- Which is Best for Small Motors?

Variable speed motor controls (‘drives’) have been around for many decades.  In the early years, application and budget were the primary decision criteria for choosing between a DC motor/drive package and AC equivalent.  While this practice continues, the advances in AC drive technology have made the decision more complex to where either AC or DC meet application requirements.  The decision criteria are broader and now include:

  • Application Requirements
  • Ease of Installation and Operation
  • Cost and Availability
  • Maintenance and Support
  • The Impact of Brushless DC

 A quick review of published information on this subject yields a preponderance of articles that lean toward AC being the better choice, especially with the advent of lower cost, more capable AC variable frequency drives (VFD’s) – drives that produce from an induction motor the kind of speed/torque response previously found only with DC permanent magnet motors.  But these same articles concentrate on larger motors – the majority of drives and motors sold in terms of annual units are fractional to 2HP size motors.

The article will focus on AC vs. DC drive selection for speed and simple direction control of motors 2HP and smaller

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