EMA Inc. | Norcross, GA | Tech Articles

Water Treatment: Making America Great

(Eddie Mayfield is the President of EMA, a company specializing in Electronic Motor Controls with particular expertise in Water and Water Treatment facilities) I had the opportunity to visit St. Petersburg and Moscow a few years ago. Both are beautiful cities, much nicer than I anticipated. St Petersburg, with its beautiful art and history is striking. I was amazed at how picturesque Red Square in Moscow was. Both cities were great to visit, the people were wonderful, and I hope…

Rockwell Allen Bradley Powerflex 7000 Shorting Issue

We recently had a customer sustain significant damage on their 2500 HP Allen Bradley Powerflex 7000 medium voltage VFD due to degraded rubber O-rings designed for reducing noise between the SGCT and the heat sink it sits on. After some digging, we found this to be a known problem in this Rockwell medium voltage VFD. In November of 2016 an engineering note was released in the Rockwell Knowledge base regarding the Powerflex 7000 medium voltage VFD: note 969771 states: “In…

Precharge Circuit for Medium Voltage MV VFD

It is common practice to have a precharge circuit in almost all low voltage VFDs, although this is not the case in MV VFD design. Inrush current can cause major damage to a medium voltage VFD. This blog describes how and why this damage occurs.