Saturday, March 7, 2009

How to find the right AC Drive for you

When looking to buy an AC Drive, you need to know a few things to mention when calling a local AC Drive distributor. I'll touch on these and a few tips to keep in mind.

Before shopping around here's what you need to know for basics:
  • Input Voltage
  • FLA (Full Load Amps) on the motor nameplate or spec. AC Drives are actually sized by amps/current not HP (horsepower). Although most consumers rarely size by current, it's the safest method. If you compare similar drive brands by HP and look at the continuous current rating you'll be vastly surprised. Some brands exceed the NEMA FLA for the HP it is rated for (FYI this extra current can bail you out on a tough load). Some brands cut it close. Others have introduced a smoke and mirrors approach with terms like Heavy Duty, Light Duty. Proceed with caution in selection on brands using this terminology.
  • Application-What are you using this for? Is it a conveyor? Is it a fan? Maybe a pump (if it's a pump, know which design type it is, *NOTE* be careful with positive displacement pumps!*)
  • How do you want to control it? Are you just going to use the keypad for starting and stopping? You might want to use remote control via push buttons for starting stopping etc. Also, do you want to give the variable speed drive (AC Drive) a variable speed reference signal from a speed potentiometer or set it using the keypad, or send a 4-20ma signal from a transmitter? If using the keypad, are you going to mount it on the front of the enclosure?
  • What type of environment is it going to be in? If you're not mounting it yourself in a control cabinet do you need to be able to connect conduit (some drives are rated IP20 for their enclosure which is sort of finger safe but you don't have a landing area for conduit)? Do you know the Nema rating of where the AC drive will be mounted?
  • Do you need any form of communications for the AC Drive? Ethernet, Modbus, Devicenet, Profibus etc.
  • Do you have any breaking requirements? Is it a stopping brake, holding brake, emergency stop application?
  • Lastly, this isn't a dealbreaker but ask about tech support via phone or locally. Good tech support is a great intangible often overlooked. Sure, you need to take the time to read the manual, properly wire the drive to the AC motor and attempt to get it running. However, sometimes you may need a little help.

There are a lot of brands out there. Here are quite a few in no particular order (and just because they are listed does not mean I endorse them, be sure to do research on any you are looking at). AC Tech, ABB, Baldor, Cutler Hammer, Emerson/Control Techniques, Danfoss, Fuji, GE, Hitachi, LG, Mitsubishi, Rockwell/AllenBradley, SqD/Tele, Vacon, Yaskawa.

Good luck!

Industrial Electrical Products

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