Phase converter help

Gahagan

Gahagan

Well-Known Member
Ok so I was playing on ebay and saw a surface grinder near me. I thought ill bid $500 not thinking I would win it since they usually start out around $1500 and go up form there, well to my surprise I won the thing. The only down fall is it is 3 phase. I am now looking for phase converters. Can some one tell me if this thing will work for a surface grinder.
http://www.ebay.com/itm/3-5-Hp-Stat...721?pt=LH_DefaultDomain_0&hash=item4173c84bf1
or
http://www.ebay.com/itm/1-3-Hp-Stat...538&pid=100005&prg=7683&rk=2&sd=281115380721&
 
Shoot man,I thought you were going to show us pictures of a surface grinder.:biggrin:
To answer your question,yes those will work,just get one sized for the motor on your surface grinder also get one for the proper voltage. Call the phone number that is in the information to be sure.
 
My suggestion is that if you're going to use a static phase converter, get one rated at least double the HP you intend to use it on.....the problem with static converters is that they will only allow about 1/2 the rated HP on the machine they're used on.
 
Using a 4hp static converter WILL NOT give you 2hp out of a 2hp 3 phase motor.
The rating on a Static converter is simply relative to the capacitor size which is used to start the motor. Once the motor starts, these capacitors are disconnected via a relay and no longer have any bearing on the output of your motor.

In other words, a static phase converter is really just a motor starter, and you're really only running on one phase of your three phase motor. In the long run, this is typically pretty hard on the motor, and not a very good nor efficient way to run a machine. They're much cheaper than a rotary phase converter, but probably will end up being more expensive in the long run.

A rotary phase converter is a better choice, as it will give you true 3 phase power, but it's only about 75-90% efficent, so you would still want a bigger "idler" motor (I.E., the rating of your rotary converter) to run your machine.
One other advantage is that you can run multiple machines at once if you get a big enough rotarty converter, but the major disadvantage is the up front cost. You'll probably pay $3-500 bucks for a 5hp RPC.

There is a middle ground though, which would be my personal recommendation if you're on a budget, and that is to get a VFD (Variable Frequency Drive)

If it's a 2 hp motor, then a 2hp or 1.5kw VFD will be plenty. This gives you 3 phase power as well, but it's more of a "simulated" 3 phase. Still MUCH better than using a static VFD, and it also gives you a little more flexibility with speed adjustments, circuit protection, etc...

I found a decent (albeit chinese) VFD for about $130 on fleabay, and I use it for both my surface grinder as well as my knee mill.

If running more than one machine though, you'll have to do it independently. I just wired an outlet into my VFD and plug whatever machine I'm running into it. You can also rig up a switch panel for each machine, but it was easier/cheaper for me to just run the plugs.

http://www.phaseconverterfaq.org/howitworksphaseconverter.htm

There's a little more info.
 
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http://bit.ly/18l1dbW

This is the one I have.
You'll need to put it in a dust proof cabinet with adequate circulation/ventilation, but it's hard to beat for the price.


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Andrew,

SO I can return the static phase converter and use this correct? How does this work and how would I set it up?
 
You can return the static converter.

As for hooking up the VFD, you'll need 220vac for the input. Your ground and 3 phase leads will then tie into the output of the VFD.

I wired a switch for my input so I could easily shut the VFD off without flipping the breaker.

Then it's more/less just a matter of programming your parameters into the VFD and maybe wiring some external controls if needed.

I will say that the manual can be a little confusing if you've never programmed a VFD before.


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If you are still having issues getting up and running, send me a pm and I can make a house call. I added a switched motor overload to the input of my VFD for on/off and so it will trip before breakers.
Find a converter rated for 3hp and you should be fine. If you have to power available, i would buy one that requires a 220 input. I just bought a Leeson Speedmaster and love it. if you have issues with wiring or hookup, send me a pm and i can come visit, just down the road in Sanford. for most uses, the factory settings are ok.
 
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I found the cheapest way to go is to build a rotary phase converter, that is what I did around 17 years ago and have been running all of my three phase applications happily ever since. The only problem is that I cannot actually remember how I did it, but it has to be fairly simple if I managed to pull it off. I will look and see if I kept any decipherable notes.

I do remember that all you really need is an old three phase motor and a mechanism to start it, some Fred Flintsone it and just use a pull cord around the shaft, but I use a starting capacitor with a push button mechanism. Some run capacitors, and some knowledge on how to use them, are useful for smoothing out the running of the other motors.
 
You might be better off just putting a single phase motor on the machine.

I made a rotary converter for a 10 horse a long time ago, only because the 3 phase motor on my machine was a very low rpm and couldn't find a single phase.
 
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I just came back to this to put in some about VFDs and see that it is already being covered. The other advantage to a VFD is that you can control the speed of the motor. On a surface grinder I don't know if that is an advantage. I have several customers that are using one VFD to run a belt grinder and a disk grinder using the system that Andrew described. When I started selling VFDs I looked into getting cheaper VFDs and putting them in an enclosure. I quickly found out that by the time you purchase the enclosure, filters and a fan it is cheaper and much more convenient to buy the NEMA4X VFD to begin with. For the plugs and outlets Andrew describes you can use common "Kitchen range" plugs and outlets. Just make sure that you have 4 prongs. If you are running more than one machine all motors should be the same hp and rpm. Check out my web-site and let me know if I can help you. If you would like to discuss this further or have questions don't hesitate to call or e-mail me.
 
I guess I should add a couple of notes, as Wayne has pointed out some very important considerations:

For my enclosure, I have my VFD in a small wooden cabinet that was always in my shop (in other words, it was free)

I ran cables and fittings to very tight tolerances, and drilled some small holes in the bottom for circulation. It probably wouldn't hurt to wrap a little filter material around the box, but based on it's proximity to the biggest "dust makers" in my shop, it should be ok. Not a bad idea to hit with a vac or some compressed air every now and then though.

I've seen some guys put them in a cheap tool box. The biggest concerns are circulation (to keep the unit from overheating) and being protected enough to keep any dust out of the circuit boards.

IF you do end up running two differently sized machines (say a 1hp AND a 2hp), then realize that the 1hp machine won't have the same kind of circuit protection built into the drive that your 2hp does, as the parameters will be set for the 2hp machine.

That means that your 1hp machine will have to pull the same amount of load/over current that would trip the VFD on a 2hp machine, before the 1hp machine shuts down.

That said, my 1hp surface grinder has some built in circuit protection independed of the VFD, so I'm not as worried about burning up my motor on 2hp drive settings. It simply means that I can't depend on my drive to protect my 1hp machine, unless I change the parameters every time I change machines, and that just simply isn't feasible.

There may very well be a way to set the drive up on a computer so that I can switch paramter settings quickly and easily, but that's not something I want to invest time and effort into at this point. That, and it'd be much more cost effective to just buy another drive. hahahah

As for any RPM differences, VFDs are based on Hz (frequency) for speed changes, so if you just keep it programmed to 60Hz then you'll be fine. I just use the belt pulleys on my mill for speed changes, and my surface grinder is a constant spindle speed, so I don't have to worry about it. If I were to start using my VFD for speed changes, then I'd have to make sure to account for that when I switched between machines.

As for the plugs, I'm just running a couple of 20A 4 prong plugs to a 20A outlet, and it works fine. I could have gotten way with just a 15A plug, but Menards didn't have them.
 
Kevin R. Cashen said:
I found the cheapest way to go is to build a rotary phase converter, that is what I did around 17 years ago and have been running all of my three phase applications happily ever since. The only problem is that I cannot actually remember how I did it, but it has to be fairly simple if I managed to pull it off. I will look and see if I kept any decipherable notes.

I do remember that all you really need is an old three phase motor and a mechanism to start it, some Fred Flintsone it and just use a pull cord around the shaft, but I use a starting capacitor with a push button mechanism. Some run capacitors, and some knowledge on how to use them, are useful for smoothing out the running of the other motors.
Click to expand...

I thought about going that route... buying a static converter and hooking it to a 3 to 5hp 3 phase idler motor.

The 2hp vfd was a lot more "turn key" for me though, and even if I built it myself, it'd probably cost a littler more for a RPC than a VFD.

Now, if I was pricing out a namebrand VFD like a KBAC-27d or simliar, than it would be cheaper to build a rotary, assuming you got a good deal on the motor.
 
ARCustomKnives said:
I guess I should add a couple of notes, as Wayne has pointed out some very important considerations:

I ran cables and fittings to very tight tolerances, and drilled some small holes in the bottom for circulation. It probably wouldn't hurt to wrap a little filter material around the box, but based on it's proximity to the biggest "dust makers" in my shop, it should be ok. Not a bad idea to hit with a vac or some compressed air every now and then though.

IF you do end up running two differently sized machines (say a 1hp AND a 2hp), then realize that the 1hp machine won't have the same kind of circuit protection built into the drive that your 2hp does, as the parameters will be set for the 2hp machine.

That means that your 1hp machine will have to pull the same amount of load/over current that would trip the VFD on a 2hp machine, before the 1hp machine shuts down.

That said, my 1hp surface grinder has some built in circuit protection independed of the VFD, so I'm not as worried about burning up my motor on 2hp drive settings. It simply means that I can't depend on my drive to protect my 1hp machine, unless I change the parameters every time I change machines, and that just simply isn't feasible.

There may very well be a way to set the drive up on a computer so that I can switch paramter settings quickly and easily, but that's not something I want to invest time and effort into at this point. That, and it'd be much more cost effective to just buy another drive. hahahah

As for any RPM differences, VFDs are based on Hz (frequency) for speed changes, so if you just keep it programmed to 60Hz then you'll be fine. I just use the belt pulleys on my mill for speed changes, and my surface grinder is a constant spindle speed, so I don't have to worry about it. If I were to start using my VFD for speed changes, then I'd have to make sure to account for that when I switched between machines.

As for the plugs, I'm just running a couple of 20A 4 prong plugs to a 20A outlet, and it works fine. I could have gotten way with just a 15A plug, but Menards didn't have them.
Click to expand...

hi,
as far as motor protection, most VFDs have a programmable max current(say 5 amps), max current percentage(how much over that before it trips, say 125%) and time(say 15 seconds). In some applications, you may draw over max current on start up or you put a heavy load on machine. the VFD manual may give you recommendations on this.
motor speed is displayed as HZ. on the motor name plate it may say 60Hz 1740RPM. you may have to make a chart or something. 30Hz would be half speed and so on.
again, read the VFD manual. The Leeson I found allows 4 different set up programs, so you can have a seperate program for a 1.5Hp grinder and a 2hp drill press and a ???.
another important area is how the VFD starts and stops the motor. You may be able to program acceleration rate, how it stops, how quickly it changes speeds. my vfd recommends a soft gentle slow down, but it can be programmed and switched for instant stop. you may want an Estop.
the old sailor
 
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