EMA Inc. | Norcross, GA | Medium Voltage

York MVVSD Repair

York MVVSD (Medium Voltage Variable Speed Drives) series drives are used on large, medium voltage York chillers, in ranges up to 10,000 horsepower. It is common to see VFDs used in low voltage chillers and compressors, but due to decreasing costs of electronics, medium voltage VFDs are becoming more common because of the potential energy and mechanical savings on medium voltage chillers and compressors. For further information on how VFDs can save energy on variable torque applications, click here.…

Square D and Eaton MCC medium voltage Softstarters

We 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…

Pre Charge on Siemens Robicon Perfect Harmony VFD

One of the key features of all low voltage VFDs is their ability to softly charge the DC bus capacitors. This feature is not a readily available on the Siemens/Robicon Perfect Harmony MV VFDs. The Perfect Harmony VFD can be easily modified to include this feature. Soft (or Pre) charging the bus capacitors limits the inrush current upon power up, and prevents damage to transformers, power devices, and other connected devices. Within the Siemens Robicon Perfect Harmony medium voltage VFD…

Low Cost Medium Voltage VFDs

Medium Voltage VFDs are coming down in price as the market grows more competitive. Nonetheless, they remain expensive. The cost is not only the initial price, but the size of medium voltage VFDs means the installation costs are significant. All that said, at EMA we love medium voltage VFDs, enjoy repairing them, and selling them. They are very reliable, and are becoming more and more commonplace. One way to greatly reduce the purchase price and get low cost medium…

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…

Medium Voltage Drives