Upcoming Webinar:  Common Faults On Medium Voltage VFDs and How To Troubleshoot Them   Register Now →

Square D and Eaton MCC medium voltage Softstarters

Medium Voltage SoftstarterWe work on quite a few Square D and Eaton MCC Softstarters.   Most of them, as it turns out, are actually manufactured by Motortronics. Motortronics has a done a great job at capturing the medium voltage softstarter market.  Square D, Eaton, and other MCC manufacturers simply brand label the Motortronics softstarter and install.

This isn’t to denigrate either Square D or Eaton MCC medium voltage softstarters.  Brand labeling is a common and efficient practice by a number of MCC medium voltage softstarter manufacturers.  Toshiba, Schneider, ABB and others do it.  The Square D softstarter is called a Motorpact, but it’s in reality a Motortornics medium voltage softstarter.

Softstarters work by limiting the inrush current during start.  The medium voltage softstarters  work well, but the downside is you are limiting the motor’s ability to generate torque.  IF you have a hard start application, such as a positive displacement pump starting into load, you might consider a VFD instead.  (See “When should you use a VFD as a softstarter?”)

Servicing the Square D and Eaton MCC medium voltage softstarters is fairly straightforward.  The Motortronics softstarter used by Square D andEaton MCC Eaton MCC uses thyristors to limit current, then once the motor is at speed, a vacuum contactor is closed to put the motor across the line.  This limited duty cycle allows Motortronics (Square D and Eaton) to use smaller heat sinks and conserve space.  That’s one reason you can fit a fairly large Motortronics medium voltage softstarter inside a Square D or Eaton MCC.

The Motortronics softstarter is quite reliable.  When failures do occur they are most often either thyristor failures, or contactor issues.  More rare are circuit board failures. Tuning can also be an issue.

The Square D and Eaton MCC medium voltage softstaters do have tuning parameters.   Getting them out of tune can result in a failure to start, or if it does start, failure to limit current as designed.  EMA Service Engineers can assist with repair, tuning, installation and application of medium voltage softstarters of all brands.  (See Electric Motor Softstarters: Repair and Operation)

Call us world wide at 770-448-4644, or use any of the digital contact methods on this page.  No One, Anywhere, is Better at Drives (or softstaters) than we are!


One Response

  1. I am an electrical engineer for an electric cooperative. We have a power company that we’re requiring to install soft-start or vfd motor starters for their existing pumps. We are assisting them in finding an acceptable manufacturer. Therefore we are looking for the closest Square D Rep, near Ebensburg, PA.

Leave a Reply

Your email address will not be published. Required fields are marked *

Get the EMA blog straight to your email

Get the latest and freshest content on managing your drives.
Related Articles