We get this question a lot: “Do you guys work on Manufacturer X’s drives?” and the answer is always “Yes”. EMA is not a jack of all trades, but we’re a master of One: Medium Voltage Variable Frequency Drives. In today’s world, good work is hard to find and there are few people more valuable than your plant’s handyman. Jack-Of-All-Trades types are very hard to find and deserve to be treated right, they often keep things running that no one else wants to deal with.
However, despite their best efforts, a Jack-Of-All-Trades guy simply cannot be expected to work with Medium Voltage Variable Frequency Drives, even if he’s “dabbled” with low voltage drives. As we’ll mention below in greater detail, there are significant differences between working on low voltage drives and medium voltage drives. Just because you have worked on low voltage drives DOES NOT necessarily mean you can work on medium voltage drives. What makes them different?
Topology
Low voltage VFD topology is almost universal throughout. The way the input is rectified and the output is created is just about the same no matter who makes the drive. Medium voltage VFD topology does not follow this model. Because of patents and differing ideas on this relatively young technology, there are numerous ways that medium voltage drives are constructed, and EMA has seen most of them all. This can cause confusion to a Jack-Of-All-Trades type. Do they use diodes in the rectifier section, SCRs, or something else like IGBTs? Does the DC bus use oil-filled capacitors, film-type, or none at all? Is the output cascaded? How many levels of output exist? These numerous nuances are the reason why you need experts at EMA. We’re extremely proud of the knowledge our field service engineers have and we’d put ourselves up against anyone in the industry, including the manufacturer. Understanding how the drive is laid out is integral to troubleshooting properly, not everyone can do this.
Safety
Low voltage drives are typically 230 or 460 volt, while medium voltage drives are commonly in the 2,300V to 13,800V range. Modern medium voltage drives have multiple interlocks and safety mechanisms in place to prevent anyone from accessing a ‘hot’ cabinet, so the argument could be made that MV drives are safer to work on than LV drives. However, wiring, terminations, arc gaps, and shielding are all different when you’re dealing with Medium Voltage, making even “simple” fixes not so simple. Having no experience in Medium Voltage not only puts personnel in danger, but your multi-million dollar equipment as well. Worker safety should be the #1 priority in any facility, and it simply is unsafe to have non-experienced people working on MV drives. Most people don’t come back from a shock at medium voltage; your Jack-Of-All-Trades guy deserves to be safe, it simply isn’t worth the risk.
Investment
The low voltage drive market is a commodity-based industry, where it is often cheaper to replace the entire drive than replace it. A 5 HP drive that costs $250 doesn’t really have the need for a “drive expert”; if they blow it up, then replacing it won’t cost you much. This is different than it was 30 years ago. When EMA started in 1990, our primary business was repairing small AC and DC drives and circuit boards, but we’ve adapted over the years as the price of components has gone down. Medium Voltage VFDs, however, cost in the hundreds of thousands of dollars, so paying for an expert is well worth the investment. A power cell alone on a 1,000 HP drive is going to cost you around $20,000, so mistakes in setup and wiring is extremely costly. Would you trust your big money investment to someone who isn’t familiar? It’s simply not worth the economic risk.
Size
When EMA first dove into Medium voltage in the mid-2000’s, we had to relearn how we take drives apart. Most of our technicians were used to small drives that required small hand tools to work on them. We invested significantly in large, mechanical tools, torque wrenches, and rigging devices to work on the power electronics that accompany medium voltage variable frequency drives. A soldering iron and a set of jeweler’s screwdrivers are no longer gonna cut it. Someone who doesn’t own and isn’t used to working with these tools is simply not qualified to work on MV drives.
Programming
The majority of low voltage drives are easy to program and extremely user friendly. Many manufacturers offer simulation software to “practice programming” and now have smart phone apps that can program the drive via Bluetooth. Most low voltage drives come with free (sometimes you have to buy a special cable), easy to use, commissioning software. With few exceptions, a modern low voltage VFD works out of the box on most applications, anyone with even minimal experience can get it going; there are thousands of YouTube Videos walking you through how to startup low voltage drives. The medium voltage VFD world is completely different. I offer you a challenge: try to find software to program and commission a medium voltage drive on the internet; I promise it will prove to be a frustrating, if not impossible task. Manufacturers, know what we know: troubleshooting, programming, and commissioning Medium Voltage Variable Frequency Drives should only be done by experts. EMA offers startup on most brands of medium voltage variable frequency drives, including ones new to the market. We’ve made the investment in the software tools already, so you don’t have to. It would be hard to completely ruin a drive due to programming, but you can very easily prevent it from working. Don’t trust this process to a Jack-Of-All-Trades guy, bring in the experts who know what they’re doing.
EMA doesn’t do a lot of things well, but we do one thing well: Medium Voltage Variable Frequency Drives. There is plenty of equipment that a Jack-Of-All-Trades can service and maintain, but leave your MV drives to the experts. Ferrari owners don’t take their high-priced cars to Joe’s Garage down the street and you shouldn’t leave your expensive, valuable MV drives to just anyone.
Let EMA be your one-stop-shop for all medium voltage VFD service, no matter what brand you have. Let us prove to you that No One ANYWHERE Is Better At Drives Than We Are!
