VFD Questions

[David L. Anthony]

I recently aquired a Delta 43-373 3 hp 3 phase shaper. I don't have access to 3 phase power, so I've decided to purchase a Variable Frequency Drive. I'll admit that I am ignorant on this subject and was looking for a little guidance. I am confused as to where in the "line" the VFD goes. Is it used in place of the starter? I noticed that there are VFD units that have what looks like start/stop switches on them. Could one of these replace the motor starter and manual start/stop switch? The shaper is in great condition and I got it free, so I can spend a little money getting it up and running.


Dave

[Peter Kuhlman]

So - you have single phase power I assume at 230 volts?
If so, yes a VFD will provide 3 phase 230 volts output - BUT only if the VFD is upsized. Will also work if you have single phase 480 input and can wire the motor as 480 and you purchase a 480 volt drive. That depends upon the manufacturer. Allen Bradley requires a 50% upgrade to run single phase input - so a 3 hp motor will require a 5 hp drive. You need to watch the incoming current draw requirements. The drive is normally installed downstream of a disconnect device. Can be a 2 pole circuit breaker in a panel. You will need something for the start-stop control and can be any kind of switch or non-momentary button or a button with holding contacts. Normally for shop equipment, you would want full 60 hertz output and the drive will allow you to ramp it up so no current surge to contend with. Great way to do what you want with lots of flexibility. Normally, the single phase input leads are connected with the center connection having no wire. Setting up a drive can be a little intimidating as there are lots of parameters that can be set. Some have a nice start-up routine that walks you through the required steps.

We do this all the time in the oilfield.
Pete

[Dick Strauss]

David,
I'm not an expert in the field so take my comments for what they are worth. Check with an expert before making any buying decisions and making any electrical connections.

The VFD goes between your 220V/1ph standard power line from the wall and your 220V/3ph power line input on the shaper (it converts a 220V/1ph input to a 220V/3ph output). You should be able to use all of the same switches already on the machine in addition to those on the VFD panel. Some VFDs will not put out the full rated hp with a 1ph input. Check to make sure before you buy! It will also allow you to have some speed control.

Some folks have had good luck with units like this... http://www.factorymation.com/s.nl/it.A/id.198/.f

Good luck,
Dick