VFD on your Stock Feeder for Speed Control?

[Chip Lindley]

Since I have a nice big RPC, I never entertain the thought of using VFDs to power 3-phase machinery. But, it just dawned on me! A VFD might be just the ticket to slow down a 3ph stock feeder when the need arises to run it slower than 13 fpm. Anyone preceeded me by putting this thought into action? How did it work for you?

[Rick Lizek]

Haven't tried that one but no reason it wouldn't work. VFD's for 1 hp or less are inexpensive and you can get them to run on 120 volts single phase. A friend has a small drill press set up exactly like that.

[Dave Cav]

It should work fine. For this application I'd suggest looking at a GS1 drive

http://www.automationdirect.com/adc/Overview/Catalog/Drives/GS1_(120_-z-_230_VAC_V-z-Hz_Control)

because it has the speed control pot right on the front panel. Some of the other low end VFDs require a separate speed control pot. I have one on my drill press and one on my mortiser and both work fine. The only comment I have about them is the fan runs all the time and I find the noise a little annoying, but if you only have it powered up when you're using it then it won't be a problem.

[Chip Lindley]

Thanks guys! I'm "Old School" in most woodworking respects, but not opposed to innovation when it presents a real advantage. I was almost 50 before I became "computer savvy". Now I don't know how I got along without a laptop!

[Lewis Cobb]

It should work fine. For this application I'd suggest looking at a GS1 drive

http://www.automationdirect.com/adc/Overview/Catalog/Drives/GS1_(120_-z-_230_VAC_V-z-Hz_Control (http://www.automationdirect.com/adc/Overview/Catalog/Drives/GS1_%28120_-z-_230_VAC_V-z-Hz_Control))

because it has the speed control pot right on the front panel. Some of the other low end VFDs require a separate speed control pot. I have one on my drill press and one on my mortiser and both work fine. The only comment I have about them is the fan runs all the time and I find the noise a little annoying, but if you only have it powered up when you're using it then it won't be a problem.

Dave - sorry for the hijack. I see you mentioned you put a vfd on your drill press. I have been thinking about this for some time but don't know what it all involves. I have a delta dp with a motor that can be wired for 120 or 240 single phase. So I have to look at a different motor as well as the drive ? Do you lose torque at lower or higher speed settings?

Thanks,
Lewis

[John Ferandin]

Chip,
A VFD on a three phase PF is the way to go.
I use the GS1 mounted under the shaper/saw table to keep it out of the dust zone.
The switch box on the PF has no capacitors in it because it is three phase so that space if perfect for two switches and a potentiometer.
I have an on/off switch, fwd/rev switch, and speed control mounted right there.
Very easy and works great. You can even vary the speed as you cut depending on the grain about to enter the cutting zone.

When ordering the VFD remember to order shielded control cable for the switches. Hard to find locally and very reasonably priced from www.automatiomdirect.com

good luck,
john

[Rick Fisher]

Dave - sorry for the hijack. I see you mentioned you put a vfd on your drill press. I have been thinking about this for some time but don't know what it all involves. I have a delta dp with a motor that can be wired for 120 or 240 single phase. So I have to look at a different motor as well as the drive ? Do you lose torque at lower or higher speed settings?

Thanks,
Lewis

Lewis.. VFD's are usually used to control 3 Phase induction motors .. Even on a 3 Phase motor, you have to be careful that you don't run it too slow, with high torque, for too long... The motor can overhead, and will certainly run hotter because the fan is turning slower. Additional fans can be installed if its mandatory..

Universal single phase motors and DC Motors can be run variable speed in single phase.

I believe with a capacitor start, centrifugal switch, single phase motor, which most of our tools have, and which your drill press likely has, you cannot slow the motor down much without burning out the centrifugal switch, or the starting capacitor..

I am no expert, but the switch activates when the motor reaches speed, so if you slowed it down, I would assume it would activate the start cap again..

I am probably confused, but whenever I try to answer a question like this .. someone who actually knows usually comes along and corrects me :D

It is my belief that DC motors, because they use a commutator, can be slowed down by lowering the voltage, or by lowering the current.. This should cause a reduction in torque..

An AC motor is slowed by changing the frequency.. so the voltage should stay stable. European motors are often 50hz .. while North American motors are often 60hz.. To slow a motor significantly, you would be well under 50hz.. IMO .

[Rod Sheridan]

Rick you are mostly correct.

You cannot reduce the speed of a single phase motor that has a starting winding controlled by a centrifugal switch.

You are correct that it's because the switch will engage the starting winding below about 70% speed.

The three phase VFD's reduce output voltage with frequency, so at half speed they would output 30 hertz and half voltage.

A VFD is a great idea for a 3 phase stock feeder, in fact many have built in VFD's.

Regards, Rod.

[Lewis Cobb]

Rick / Rod -
Thanks for the VFD tutorial :)
It sounds like the approach that I would have to take is
a) find a 3 phase motor to replace the existing one on my DP
b) then buy a VFD that would hook up to the 3 phase motor.

I just started the "google research" and it appears that a VFD - or some of them at least - take 115 / 230 1P input and convert to 230 3P output.

Do you normally spec the 3P motor with the same HP as the 1P motor that you are replacing in such a project?