actually depending on the size of the lathe and the size of your converter you may be able to run them both at once. but if your in a small gargae shop the chances of you running both of them at once is slim to none, at least i haven't figured out how to run both at once. 2 hands too many feeds. ask away i will be happy to help talk you threw hooking it up. and if you are wondering i am an electrical contract with over 10 years in the field.

 

Go to www.automationdirect.com/drives I'm looking at there book and it shows A 230 volt single phase input/230 three phaes output AC drive for 1 hp. for $159.00.

 

I vote for variable frequency drive.

I ran my Bridgeport mill for several years using a chatter box. While that worked fine, was always fussing about having to move belts around the pulleys to change speeds, and it always seemed that the speed wasn't "right".

Last winter I hooked up a Teco/Westinghouse VFD and I will NEVER GO BACK.

Almost instant control of direction and speed. Programmable accel and decel times, electronic braking, current and overload limited, next to idiot proof. Since then I have bought several VFDs from this business and have been very happy with all of them.

http://www.dealerselectric.com/

You can run your Bridgeport with model # FM100-202-N1* which their website lists for $258.00

You'll never want to deal with rotary phase converter or chatter box again after using a VFD!

In fact, I'm hoping that the single phase motor in my Clausing lathe gives me a problem so I can install a 3 phase motor and control it with a VFD!

 

Can someone explain to me how there VFD work?? i guess i am lucky i don't have to change belts around on my bridgeport so having a converter that varies the speed and direction never crossed my mind.

 

I went to their website today and they also have a 230V single phase input/230V three phase output 3HP VFD for $319.

If I'm not mistaken, a VFD more-or-less works like a CD player: Incoming power is converted to DC, then chopped up using a digital-to-analog converter and smoothed out again so it looks like an AC wave.

Until I read this thread, I never thought of using a VFD to run a mill A mill is on my wish list for my dream garage...

Cheers,
Eric

 

eehoepp,

Your explanation is a pretty good analogy, and close enough for this discussion.

If you have a "typical" Bridgeport vertical mill, the motor is only a 1.5hp motor and the 2hp Teco drive I am using handles it just fine.
I even POWER TAP in some situations without a tapping head..... One little push of the Forward/Reverse button and it changes direction in less than 2 seconds. Press STOP and the controller stops it quicker than if it had a mechanical brake. All of these parameters are user programmable.

Like I said before, I just wish my single phase lathe motor would hiccup so I can justify swapping it out for a 3 phase motor and an electronic drive. There is a "scrap" guy locally who sells me 2, 3, or 5hp 3-phase motors for $15. He says they are too small for his "industrial" customers to buy and they don't have enough copper for him to salvage them....

 

ok thanks for the simple explanation. but here's another question for you all. on a rotarty converter you supply it with 240 v and you get 240 v 3 phase out of it. with the VFD you supply it with 240v single phase can you get 440v 3 phase out of it??

 

sparky30_06,

None of the units that I am aware of can do voltage step-upm you either get a 220/230V unit or 440/460V unit. All of the specifications that I reviewed show output voltage proportional to input voltage, they just add the extra phase and give you very wide control over the frequency of the output.

If you want to operate 440/460 3-phase machinery with 220/230V single phase power, I think you would need to use a single phase step-up transformer to get the 440/460V input the 440/460 VFD would require. Just remember that you 220/230 side current would be approx. double the 440/460 side....

 

ok just checking. i have a guy that bought a 3 phase table saw and radial arm saw. both of them MONSTERS but they are wired for 440 v. and they both have electric brakes on them. and everything i have ofund so far is to basically get a step up transformer set up for them. he has 3 phase in his shop but throws a curve my way the other day and says he is changing shops and some of the ones he is looking at are only single phase shops. so i'm just trying to come up with solutions to these possible problems.

 

Your explanation is close, but some additional detail might be useful.

Incoming AC power is rectified to DC using diodes and a capacitor bank. A block of 6 IGBT transistors synthesizes a three-phase waveform using pulse-width modulation of a high frequency carrier (typically 3 Khz to about 16 Khz). These "integrated gate bipolar transistors" are fairly impressive, since they can switch 10's of amps and hundreds of volts in a matter of a few microseconds.

The output of a VFD is variable frequency, variable voltage, 3-phase power. It is trivial to run the motor in either direction. Usual frequency ranges are 0 to 60 HZ, operation to 120 HZ is possible with some motors. There is nearly infinite control over ramp rates, V/F curves, overload detection, 24 volt control wiring, etc. The drive can implement a P-I-D process control loop with an analog input if you like. The instruction book for typical drives is nearly an inch thick, but most parameters default to something useable.

One caveat comes in the nature of the produced power. It is far from a nice smooth 60 HZ three-phase sine wave. Instead, it is a modulated square wave with some very sharp edges and a lot of high-frequency noise. The motor does not care, because the inductance of the windings smooths the "choppy" input into something that behaves the same as if it were a true filtered output. Phase balance and power quality, from the motor's point of view, is much better than the typical phase converter.

However, the drive creates a lot of RFI. AM radio reception in the general vicinity will be completely destroyed. There can be issues with ground leakage and insulation punch-through due to signal reflections if the drive-to-motor leads are long enough. This is not too big a concern at 230 volts, but can be a problem at 460.

There are some drives in the industry that can convert 120 volt single phase to 230 volt three phase. It is also possible to build a 240 volt to 460 volt version. Basically, the rectifier/capacitor bank is reconfigured to act as a voltage doubler, and the IGBTs switch the resulting higher DC voltage. There is a guy on ebay that sells drives that he has rewired to use this strategy. The main cavaet is that the drive output power has to be derated, since the usual limitation on the total horsepower of a VFD is the input section, and the voltage doubling trick doesn't come for free. A 10HP drive that could power a 460 volt motor using voltage doubling would be fairly expensive.

For lots of info on machine tools, including a whole section on VFDs, try www.practicalmachinist.com.


I ended up using a VFD to power a three-phase submersible pump to provide water for my home. The 3HP drive cost about the same as a single phase motor-starter, and the 1 second V/F ramp rate avoids the need for 3 large pressure tanks while still providing the full 27GPM output of the pump. It has worked flawlessly for two years.

 

This is exactly why I am not married. Everytime I think I have the the right one, a better one pops up. Too many choices. Now I'm going to have to look at VFD's.
So if I hook it up to a VFD, what gear and pulley do I use? High gear with the big pulley and then run the motor to lower RPM's????
Or low gear and small pulley and redline the motor? I think the motor runs at about 1500 RPM normally.
Steve