3 phase 20" Jointer Questions

I'm looking at a 3 phase 20" jointer, and the guy has it running off of 220 right now. He starts it up with a smaller 1.5 HP motor attached to an idler pulley, before engaging the start button on the jointer. It only produces between 1/2 to 2/3 the rated 8.5 HP.

How effective is this set up with an idler pulley and starter motor? My other choice would be to get a phase converter, so either way there's added cost to be factored in. Which route would cost less and/or provide better performance?

The machine has been completely reconditioned 5 years ago, but has its original 8.5 HP motor and was used primarily in a shipyard. All the knives and cutterheads have been sharpened. The asking price is $1800 CDN, is this too high?

Also, operating costs for a 20" vs. an 8" jointer. Are they significantly higher for your electricity bill? And for sharpening the knives, how much more will it set you back?

Thanks,

Aaron

Aaron..
I have to say that this is a clever way of getting around the static phase converter.:D Something to keep in mind.

A three phase motor is not self starting on single phase power but it will run on single phase power once started. This is called single phasing. You will get a signficant loss of power off your nameplate rating by running it this way. The loss is about 1/3 with the actual derate being a function of the square root of 3 as if that really matters to woodworkers.:rolleyes:

For most of the work done by a hobby shop, this will not matter much. Lumber these days most often comes in less than 10 inch widths and if your edge jointing, you will not notice the loss of power at all. If your taking a 1/2 inch cut on a 15 to 20 inch wide hunk of purple heart or Ipe, *YOU* will really notice the difference!

The pony motor starter is doing the same job as a "STATIC PHASE CONVERTER" so there is no need to change over to a static phase converter if that is your plan. The power loss or derate is the same regardless of which approach you take.

Clearly the best approach is to switch over to a pure three phase power supply be that from the grid or from a rotary phase converter or from a VFD. VFD stands for variable frequency drive. The VFD is a small electronic box that uses solid state semiconductor technology to generate true three phase power from single phase supplies. Folks that I have talked to who are using VFDs are happy campers. Its just that they are expensive and if you put them on every machine you have, the costs run up. The general variable speed 260 lathe uses a VFD and three phase motor to implement an infinite variable speed lathe drive which illustrates the other use for these items. By the way, this lathe takes standard 220 single phase input as well.

Should you get this jointer, you can change the current setup on your own time table. If it works, then you can use the jointer while you decide on the final course of action or save your pennies to buy a VFD. Whatever works.

As for price. Well, that is a very hard question to answer. We dont know the condition of the jointer, the year and make of the jointer or what type of jointer it is. Does it have ball bearings? Is it a wedge bed jointer or one with indpendent table ways? Certain makes of jointers and the year in which they were made can push up the price. For example, if its an Oliver, Porter, or Newman, then its value just went up. If a Porter, than its value is based on it being a model 300 and not the older babbit types.

Properly tuned up, an Oliver, Porter or Newman can very easily hold its own against new jointers such as the Martin T-54 or the German Hoffmans which represent the pinacle of modern traditional jointers today. That is ineed saying something!

Let us know more about whats up so we can help you out some more.:D

I agree with dev. what is the make of the machine and how many knives does it have. If it is a porter, newman, oliver or northfield then they are quality machines as dev says that will meet or exceed most any machine out there today for a fraction of the cost.

lou

I already answered this posting on another forum last night, but found Dev's reply here this morning and wanted to cover this again. (Dev, you're not TDKPE on another forum are you? The information is so similar.)

I'm running late so this will have to be short.

Using a pony motor to start a 3-phase motor is not healthy for the motor. This will cause an imbalance in the windings which will heat the motor more than it should be.

A static converter is NOT just a starter. The capacitors in the converter energize the third winding to help reduce the imbalance.

Since this is so short, I would suggest reading my article on building a phase converter to answer more of your questions. http://waterfront-woods.home.att.net/

Rick,

Very good article on 3 phase converters. I wish I knew more about 3 phase as I see very good equipment going fairly cheap that requires 3 phase power. I can't get commercial 3 phase where I am and I don't want to spend $2K on buying a converter just to run one or two machines. :rolleyes:

Rick... What is a "TDKPE"?

First of all Dennis, its easy to build a phase converter. I and many "Home Shop Machinists" have used home made rotory converters for years. There are plans on the internet as well as ebay to help you get started. I have a complete machine shop that is virtually all three phase in addition to my woodworking machines.

As to Ricks comments. I have to respectfully disagree on this. I designed my first phase converter myself and wound up using a three phase motor as an idler. In my first pass, I considered using capacitors. A couple of quick calculations and it was clear this would not work very well.

Sorry if this gets complex now. Three phase power is not three independent voltage sources but a phase relationship between three mechanically linked voltage sources. The phase shift is mechanical and is obtained by taking 360/3 or getting 120 degrees. So a three phase generator actually has three separate "mini alternators" spaced equally about the circumference of the rotor thus dividing the stator windings into three groups. This is the ideal goal that a phase converter is trying to duplicate. So when one measures voltage, its always relative to two points of the three points establishing the three phase relationship. For example, L1-L2 or L2-L3 or L3-L1. What connects all this stuff together is the inductive fields established by the stator in a motor or the stator "slicing" magnetic fields estabished by the DC electromagnets of the rotating rotor in the AC alternator. That is why alternators (i.e. street name generators) have DC exciters (DC generators) attached to the drive shaft.

Now, a resistive load has zero phase shift. Phase shift can be leading or lagging meaning that its either positive or negative. A coil for example can have a + 90 degree phase shift assuming we call the coil's or inductor's direction of shift positive. In that case, a capacitor will have a phase shift of 90 degrees in the oppossite direction or in our example, a minus 90 degrees. So depending on how powerful my coil is and how powerful my capacitor is, the two will prorate accordingly and work against each other leaving you with a "net phase shift". Something between +90 degrees and -90 degrees. Also note that your motors are hard core inductive loads meaning that they act as coils and will affect your overall phase shift accordingly. This can cause problems with your power company and you can pay a nice penality for haveing what is known as 'NON UNITY POWER FACTOR". This problem is solved by using a box of capacitors on your incomming line performing what is known as power factor correction. Is was from these "boxes" that we salavaged our first oil filled capacitors for building our phase converters as these are expensive when bought new!

O.K. Back to the issue at hand. The reason that a three phase motor can self start and a single phase motor or three phase motor running on single phase cannot self start is self evident. There is no rotating magnetic field with a single phase supply.

So in the case of single phase motors, you have a main run winding and a secondary winding known as the start winding. These two windings are wound together using often what is called a "skein" winding. Power is bled off the main supply and routed through a big hunkin start capacitor which phase shifts the voltage by 90 degrees. This creates a crude but effective two phase power supply which in turn establishes enough of a rotating magnetic field to self start the motor. Once the motor comes up to speed, a centrifical cut out switch, often located in the aft bell, disconnects the start winding from the power and the motor is now single phasing and running. But a single phase motor was magnetically designed to operate on the single phasing condition with a single run winding so it outputs its nameplate power rating.

As an electrical motor operates, its power output is a function of its current draw and mechanical pull. Increase the mechanical pull, and you increase your current load. That makes sense. So at idle, a three phase motor outputs the same shaft power on either single phase power (once started) or three phase power. As I begin to load the motor, this picture changes dramatically. At full current draw, a single phasing three phase motor is outputting a massively lower shaft power than the same motor running on three phase power. For a machine tool, this is a bad thing! But we are going to take advantage of this problem.

In a rotary phase converter, your idler motor (salvaged three phase motor with no shaft loading) is single phasing. There are three windings in the stator. These are either star connected or delta connected. For most smaller motors of say 20 HP and less, the star is the most frequently used configuration. Hunkin deltas are frquently used to run ski lifts. But for every generic rule, there are exceptions and in this case, there are quite a few. My oliver 10 HP louis allis jointer motor is a delta wound motor.

At any rate, in a star connection, your three windings are connected in the middle creating the star. The outputs of these three main stator windings can be called T1, T2 and T3. To single phase the motor, I will attach my 240 volt single phase power supply L1-L2 to T1 and T2. Thus, I have current flow to run the motor flowing from L1 into the first stator coil via T1 through the interconnect node and back out the second stator coil via T2 and back to the grid via L2. Now bear in mind that I have left out the starting system for this idler motor! This bad boy will not self start as I have described it here. You need to add a few more items.

As this motor single phases, the rotating rotor consummes power through Nickola Tesla's principle of electromotive induction. As a side effect, the stator field of the thrid stator winding is reestablished using borrowed energy taken by the rotor from the stator fields of the first two windings. I told you that this was all interconnected via the principles of fields and induction. Since the third field is mechanically interconnected to the first two fields by virtue of the rotor, it also means that the field is phase shifted permanently by 120 degrees which is how the rotory reestablishes the missing leg.

Now, since the phase converter technically does not generate power but rather re-distributes it, one will find that the voltage levels are not always balanced. The grid is driving your L1-L2 voltage. That is the normal 220 or 240 (depending on your utility) that you get from a two pole breaker. The voltage levels on L1-L3 and L2-L3 are going to be a bit different. In a perfect world, these would all be the same. But we can correct this if needed. The two main "run capacitors" found in a phase converter are used to shuttle voltage amoung the legs to better balance the three legs. Of course, your voltage will differ on an idle converter versus a fully loaded converter. On a grid supplied three phase connection, this situation will not occur. But in reality, these "fluctuations" that occur after the run capacitors are installed do not make much of a difference.

So back to static converters and starting rotary converters. I have seen many different schemes to start a rotary converter. The classic one is to attach a small single phase motor to the idler motor. As you turn on your small motor, it spins up the idler motor and your online. Once the idler is single phasing on its own **AND** assuming your idler can drive the pony motor slightly faster than the pony motor's sync speed, the pony actually becomes a mini induction generator. Unlike a fully syncronous alternator, an induction generator will self sycnronize its output frequency to that of the grid frequency. So in the US, your pony is pumping a small amount of 60 cycle, single phase power back into the grid.

The more popular starting systems are based on single phase motor starting schemes. You have a bank of electrolytic start caps attached to a voltage sensing relay. As you start up, your using the unused winding as a start winding. When the output of your wild leg approaches your line voltage, it trips the voltage sensing relay and takes the start caps offline. Since these are often electrolytics, you dont want to run them with AC continously as this will destroy them in short order. They are only used to start up your idler. The run capacitors are oil filled, paper/mylar power capacitors designed to run on AC continously.

This is what a static phase converter does. Its main theme in life is to supply a starting system to single phase supplied three phase motors. As its using capacitors for phase shifting, your only going to get at most 90 degrees of phase shift. Once the motor gets going, the indcutive nature of the motor will try to pull that phase shift the other direction. So yes, a static converter has wires for all three lugs T1, T2 and T3. But you will do more harm in running continously by trying to divert power to the third winding if its not a true 120 degrees phase shifted from the other two.

Also note that the clasic static phase converter has a red light on the top of the box. This is an overload indicator. If your running a metal lathe for example and this light comes on, BACK OFF NOW! As the motor rotor begins rotor lock up, your going to get excessive heat build up in the motor. The static converter will try to compensate for a reduction in rotor speed once your rotor has poped out of its maximum slip angle by engaging the start up system. That is what is does. But its a known fact that static converters *WILL* never run a three phase motor at full nameplate output because they rely on single phasing to operate.

Static converters are often used to build rotary phase converters. In this application, they are great. The idler motor will never see a shaft loading high enough to pop slip and begin rotor lock up. NEVER EVER EVER! So when one buys a static converter, you get most of the goodies needed to build a full rotary converter minus the idler motor.

Now, if I am running an application in which my application's full load condition will never exceed say 50 percent of the motor's nameplate rating, then I can use a static converter. But, the farther my loading condition deviates from idle, the more unbalanced by motor becomes. Here balance is not mechanical but electrical. This unbalance will result in the motor running hotter than normal. Is this bad? That depends on who built the motor. Motors such as the Louis Allis motors found on many Oliver, Northfield, Newman, Tannewitz, Yates, etc. machines were made to withstand massively higher heating conditions and shunt this extra heat away from the motor. Motors made overseas and used in economical machine tools are not designed to do this. Thus, using a static converter on an oliver will most likely have no noticeable affect other than reduced power output. Use that same converter on the cheaper modern machines, and you can burn the motor out if your not watching the red light!

Hope this all helps in your understanding of motors. One of the down sides to using the older industrial machines is that you *WILL* develop a working knowlege of motors:rolleyes:

Sorry Dev, I know my previous posting was confusing and rushed. TDKPE is the name of a user on another forum that posted very similar information to your first posting. I thought you may have been the same person.
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With the sheer volume of text in your last posting, I cannot be certain that we are on opposing sides of this discussion or not. While I fully understood what you wrote, I could not ascertain what your viewpoints are, so don't automatically assume this is an argumentative discussion. We might actually be saying the same thing in different ways.

The point I was making is that simply spinning a 3-phase induction motor does not necessarily make it a good phase converter without using balancing capacitors. This topic is discussed in my article, which I invite you to read. For what it's worth, there are many machinist's forums and websites that refer to my article on phase converters.

As a matter of fact, there are so many web sites that point to my article, that it carries the #1 ranking in Google under the generic searches of "phase converter" and/or "phase converters". Trust me, there are quite a few phase converter manufacturers out there that are begging me to link to their sites so they can share my ranking (but I'm nonprofit, and have no plans to be otherwise).
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The confusion on this topic is because many people think that an induction motor is the same as a generator because they are so similar. However, a generator has a separate set of field windings (or even permanent magnets) that allow the spinning rotor to generate the third phase from being driven single-phase.

There is no (or little) coupling between the phases of an induction motor because the rotor's shunted bars deliberately have little residual magnetism.

The run capacitors in a static or rotary converter serve to energize the 3rd phase windings, which in turn serve as a quasi-field-winding as the rotor spins.
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By the way just for reference, I actually have a 3-phase, permanent magnet motor sitting right beside me that I am using as a generator/dynamometer. This is identical to a 3-phase induction motor, except the shunted rotor bars are replaced with permanent magnets. When I spin this motor, it truly generates a 3-phase source without any external excitation.
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This topic has grown far too complex for a woodworking forum, so I am going to cut it off here. Since you already know how to build a converter, I don't expect you to read my article. However, if you scan down to the table I created for "Balancing" the converter, much of this discussion will make more sense.

Rick...and Dev...I'm finding this discussion most enlightening and don't think it's beyond this particular woodworking forum. SMC is "different" in that respect!! There are potentially a lot of folks here who might choose big, old iron or new Euro equipment that requires 3-phase power. Understanding how 3-phase works to a certain extent and how to get there is as important as the cutting/milling features of those tools.

Dev & Rick,

Thanks for all the info, it really helps make purchasing older 3 phase machinery a much more feasible route. The jointer was in great shape and ran fine, but I wasn't able to recognize or find more info about the manufacturer (Mccoy-Kewland). It's a huge and beefy machine, but $1800 plus setting up a converter doesn't make it a very smart financial decision regardless of the quality of manufacture. I'm going to keep my eyes open for old iron, especially 3 phase machines since they are so much cheaper.

Rick, I've been to your site before and it actually helped out a lot when I first thought I would be buying a 3 phase General 350. Turned out it wasn't 3 phase, but because I was prepared to do the work to make 3 phase work, I was the only guy who went to go check out the saw. Worked out great for me!

Thanks,

Aaron

So Aaron...
I assume from your last post that you bought the general 350. That would be great!:D

Jim, I have to agree with you. This is a nasty but critical topic. The most frequent reason given by folks for not using some of the older, industrial machines is the barrier of three phase power. The fear of going to a phase converter and the fear of its associated cost. Often it takes a small garage with a hobbyist using three phase on an old oliver or other machine to finally push a person over the fence. As for me, I am eclectic. I love hand tools and power tools. I love metalworking machines and woodworking machines. I love new stuff and old stuff. I like shaft drive and electric motor drive. I like single phase and three phase. So to get all this work in harmony, I have had to apply most of all the three phase stuff I learned in school. The only stuff I did not apply was high school geometry but the woodworking quickly filled in that excuse!:rolleyes:

Rick. As you know, there are two main types of three phase AC motors. Syncronous and Induction. The outer portion of these two motors is called the stator and consists of a bunch of flat plates stacked up along with the windings going through slots in this stack of plates. The hole in the center of this assembly or stator is what houses the rotor and the distance between the rotor and the stator is your air gap.

The most popular motor in use today is the induction motor invented by Nickola Tesla along with the corporate support of Mr. Westinghouse. In an induction motor, the rotor is made of a stack of steel plates packed together on the rotor's main shaft. These plates also have grooves or holes in them forming "passages" from one end of the rotor to the other. This assembly is then put into a special mold in an injection molding machine and molten aluminum is injected into the mold. This aluminum forms the end caps of the rotor which includes some cooling fins. But molten aluminum also fills in the "passages" between the newly formed front and end cap thus connecting the two electrically. Because all the molded "bars" are shorted together, an induction rotor is a chameleon. That is, it can take on any number of motor poles which ultimately determine how fast your motor runs. The more poles, the slower the motor. This pole count is determined by how many sub groups each of the three stator windings has and how many slots are available in the stator plates. So as you can see, this is very simple construction. For folks restoring machines such DeWalt radial arm saws, here is a world of caution. Water can get in between the rotor plates and freeze. Although this is rare, this can cause the rotor pack to exapand and crack some of the bars. A rotor growler test can help in determining this. In the case of the DeWalt motor, this can be an issue as the motor is unique to the tool. The same caution applies to most of the direct drive woodworking machines. Often, machines that are restored from rust bucket cases sitting under trees for years are susceptable to this issue. In the case of my Dewalt, I was lucky. There were no cracked rotor bars.

In the other kind of motor, life gets much more complex. Here, the rotor is built up using electromagnets. For most motors running *LESS* than 3600 RPM, these are built using bulbous shaped magnets called "Salient Poles". In those cases where your at 3600 RPM, the rotor is made by winding the magnet coils into slots milled into a large steel rotor drum. DC power is fed to these magnets using slip rings on the rotor's shaft. This is a much more complex construction and requires you to have a unique DC supply for your rotor's magnets or rotor coils. This type of motor runs at exactly its sycnronous speed which is a function of its stator pole count. This is not the same as an induction motor which runs at slightly less than its syncronous speed with the difference between sycncronous speed and real speed being called the slip.

Now some motors will cheat here. They will utilize permanent magnets on the rotor in place of the larger electromagnets. Tiny alternators also utilize this. For example, in the case of the APU alternator used to power up the A-300 Airbuss, there is a tiny back up alternator attached to the main alternator's shaft. SHould the main alternator lose field exciation, then there will be enough power from the permanent magnet alternator to get the ship back onto the ground.

For the SMC woodworker and electrical hobbyist in general, one should keep one imporant thing in mind. Regardless of which type of AC motor your talking about, the stator winding is identical. In theory, I can remove the induction rotor from a 15 or 20 horse induction motor and replace it with a homemade salient pole rotor and slip ring assembly. Attach a small DC generator to the motors shaft along with a gas engine and I now have a full bore, three phase alternator! Clearly, a practical implementation is more involved. As they say, the devil is in the details. The main point is that the stator of an induction motor is identical to the stator of a syncronous motor.

Now, getting back to the idler motor. The idler motor is best referred to as a "rotating transformer". The run capacitors job is to balance voltage imbalances between the grid supplied L1-L2 and the wild leg or created leg L3. The ilder's rotor bars are shorted together; however, since they are aluminium, they have very poor magnetic properties. The rotor's main construction however is a stack of steel, insulated plates made from a unique magnetic steel alloy specially formulated for magnetic core use. Stator packs, rotor packs, salient pole packs and transformer cores. So there is a ton of magentic field linkage going on between the stator's fields and the rotor's fields.

Do you need run capacitors? That depends. In my first phase converter, I used a super E high effiency baldor 15 HP motor as my idler. Bought this on ebay from an old warehouse ventilation fan application. According to the experts, I would need a certain level of capacitance in farads for each of the run caps. On installation of these, I found that they were wrong. Because of how baldor had made this motor, I did not need to use any run caps. I did wind up using tiny run caps to "fine tune" the voltage imbalances but these were not really needed. On other idler motors, you may need a suit case of run caps to balance your voltage imblances.

One item to note here. Not all rotor cores are identical. Baldor designed my rotor to be as frugal as possible in a motor application. This had a nasty side effect in that it made the idler harder to start. When I discussed this with an engineer from Kay Industries, he mentioned the fact that their converters use unique rotors designed for idler applications which makes starting easier. Personally, I am still researching the details on this topic so I am not the expert to ask questions to in this regard. I just have some empirical data to work from at this point. I do know that the number of run caps required and the ease by which the idler starts are inter-related.

Lastly, please keep in mind that idlers are rotating transformers. Like any transformer, they work on elctromagnetic field coupling. In the case of the idler, its mechanical rotation is how we re-establish the 120 phase shift. Had this been a true alternator (i.e. generator in street slang), the power input would be massivly higher. As it stands, I am single phasing the idler's rotor and that is all I need in terms of energy to get this thing to run. That and a little bit of core loss. This is why phase converters are as effiecient as they are.

Hope this helps in buiding your understanding of the motors that make sawdust. In the final analysis, all that matters is our ability to make chips and sawdust.:D

Yeah, I picked up the General 350. Got in touch with General and they helped ID it as a 1992 model. Saw has a little bit of surface rust and needs new fan belts, guard/splitter (would've replaced the stock one anyways), and motor cover.

Back in school right now, so it's not close by to take pics or to work on, but when I get the chance I'll post some pics.

Aaron... that is great. You are going to love that saw after a bit of TLC.:)

By the way for everyone else, I apologize for the long post I just posted. I guess that is the bad news. The good news is that this post contains most of the slog and bash theory that you need to worry about. Not much more to talk about except some minor logistics stuff.

now this old thread is a true gem!!!
tons of good info.

Thanks for all the great info DEV, I was wondering if you could shed some light on a few things that I have been told and dont know if I believe.
Are all 3-phase power supplies the same (or should be), I am aware of 208, 230, and 460-480 volt. But I have been told that some 3-phase power supplies have a higher voltage on one of the legs? Or are all three legs suppose to be the same?
Example, if I were to buy a machine do I need to find out what power it was set to run on, besides the 208 - 230 - 460? Can most motors be rewied to run high voltage (460) or low voltage (230)?
Is power around the world the same, if a guy were to buy a machine from Italy and bring it to the USA is it designed to work the same way?
Last of all can you get single phase power from 3-phase? I was told to wire my single phase 230 volt stock feeder to any 2 outputs of the magnetic controls on my 3-phase 230 volt shaper. If this does work does it hurt the stock feeder motor any?
Thanks, Troy