There are not many new plants being built these days. Yes, there are some but most of what takes place today is retrofitting of older, existing equipment in plants that already exist. This process of retrofitting older equipment to new, modern, technology can be complex. We see many instances where someone replaces without considering all of the aspects of a replacement and the motor ends up not working. This article should serve as a guide for doing retrofits on large electric motors, focusing on AC Induction motors. We also want to give credit for a lot of this information from our friends at Siemens. They do many retrofits every year with us as well as their other channel partners.
Large electric motors, those of 400HP or more, are typically referred to as Above-NEMA or A-NEMA electric motors. When it comes time to purchase one (either new or previously owned), it’s vitally important that when bidding manufacturer to manufacturer, they are all given the same parameters.
There is tremendous value in saying “This is what I want.” Without specifying, “what you want” you will simply get what each manufacturer builds. It’s like the old saying “apples vs. oranges”. If you don’t specify that everybody quote an “apple” and you just say you want a piece of fruit, you might get an apple, an orange, or even a banana!
By specifying exactly what you want, you will have leveled the playing field and stand a much better chance of getting precisely the right motor for the job.
YOU NEED A MOTOR. NOW WHAT?
Maybe you need a new NEMA standard electric motor. Maybe you need a previously owned one. In either case, there are some important questions to ask before placing the order. If you make the wrong call, it can cost you — big time.
The following will give you some tips to help make sure you don’t make that costly mistake.
OK, you need another motor – why?
This is the most important question of all. Exactly why do you need one? Was there a failure with a current motor? Has this exact same failure or one very similar occurred before? If so, maybe the motor was not the best available motor for the application. Here are some things to ask yourself in that regard:
- Did the motor have the wrong enclosure?
- Did the motor have the wrong horsepower?
- Is the motor on a VFD?
- What else? There are a variety of items that can be mishandled or misapplied. Go over them all to get a handle on the situation when the motor went down.
If you don’t figure out why it happened – how on earth can you prevent it from happening again?
You’ve decided on a motor. Sure it's the right one?