VFD wiring questions???

E

eddief

Eddie Fosnaugh
I have a few questions about wiring up my VFD to my variable speed Bridgeport.

1. Since the VFD will be used to control speed, do i set the speed change handwheel on the Bridgeport to the max speed and leave it?

2. Do I disconnect the high-low range drum switch that is on the left hand side of the head?

3. Does the drum switch have to be wired into the VFD or left disconnected?

4. After everything is hooked up, how should the Hi-Neutral-Low lever on the right side of the head be utilized? Neutral is self explanatory, but now since the VFD controls the speed, does the lever just need to be in the Hi position for all speeds, or low for that matter?

Sorry for all the questions,and I really appreciate any and all help!
 
Depends a bit on the VFD you have. If it is a three phase output type, and the mill's motor is 3 phase, then you may just want to bypass all the original electronics on the machine - sometimes there are problems with running one converter into another (without getting too technical, you can overheat things in unusual ways). If you are working with a triac or SCR device output in single phase, then you probably will have other types of problems when you try to run into the Bridgeport controller. Again ,it depends on the specifics of the units. I think I'd check with the Bridgeport people and the VFD manufacturer about compatability before I started any wiring modifications.

This begs the question, but why run the mill with a VFD if the machine is already a variable speed model? There are some potential problems, and I don't know what the upside would be. If your main goal is really to use the VFD module to convert single phase to three phase power because the mill is three phase, then I'd just set the VFD output to 60 Hz and change speeds with the Bridgeport controller. This should work ok if the VFD output is reasonably sinusoidal.

Scott
 
I recommend the following set-up:

Motor control drum sw: High, This sw. cannot be moved when the VFD is running and there should not be a need to do so. It can be removed, but there is no need.
H-N-L lever: High
Speed control handwheel: adjust for maximum desired spindle speed when motor is running at 3600 RPM ( 120 Hz). Don't worry, a quality 1800 rpm motor can tolerate 3600 RPM (120 Hz)
You should fabricate a control panel for the VFD containing the following items: Start button (green) , Stop button ( red), Forward- Reverse selector sw. ( 2 -pos.) Jog button., Speed control pot. with knob( pot wattage and resistance range as specified in VFD user manual. The VFD display can usually be detached and should be added to the control panel. It can be programmed to display spindle speed once you decide on a fixed setting for the BP speed control handwheel.
VFD frequency range: 10 Hz to 120 Hz. Jog frequency : as desired but 10 to 15 Hz usually works well.
Recommend you use standard industrial duty manual switches known as "Oil-Tight" in the trade. (eBay is a good source). You can use components from Radio Shack but they will not hold up.

There is more to consider with a VFD conversion, but this will get you started.

RWO
 
Well, I got the VFD wired up and nothing got smoked. These are really nice and quiet.

I will have to fine tune the programming some more once I figure out where exactly I want to run the handwheel for the speed. It seems that I need to find a happy medium where I get the torque I want at low speed and the top rpm that I want.

Thanks for the posts guys, I appreciate the help.
 
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