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  1. #21
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    The Ward-Leonard System has been around for more than 100 years.

    http://en.wikipedia.org/wiki/Ward_Leonard_control

    Its first application was in elevators and hoists. Also, roll mills.

    It is essentially a rotating power amplifier, wherein a relatively small amount of power can control a relatively large amount of power.

    Where the "amplification factor", K, of a Ward-Leonard system is not enough, there is General Electric's Amplidyne®, and other cross-field systems.

    (An historical question: how does one control the rather large mass of a set of individually targetable .50 caliber Browning machine guns, mounted in the turrets of a B-29, and operate these from a remote location, all without using "electronics"? By using Amplidynes, of course).

    http://en.wikipedia.org/wiki/Amplidyne

    In its machine tool application, the Ward-Leonard system is quite enough to control a 3, 5, or even a 20 HP motor.

    Carla is close to the mark: an elevator technician should be able to fix the Ward-Leonard System in a 10EE. But an industrial control technician may be better suited to the job. All the information necessary is printed on a single sheet, and just about the only parts which need maintenance are the brushes, which are still available from Reliance.

    If the noise from the M-G is truly objectionable, and you have a convenient place to mount the it in an exterior "dog house", then that is a possibility, too, although you may have to increase some wires by a size or two to minimize system losses.

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    The history of the 10EE's drive system is not unlike that of related drive systems, as used in elevators and hoists.

    Perhaps the best description of the Ward Leonard system comes from Wiki's entry on its inventor, Harry Ward Leonard (sometimes called Harry Ward-Leonard):


    The Ward Leonard motor control system was Mr. Leonard’s best known and most lasting invention. It was introduced in about 1891 and soon became the most widely used type of electric motor speed control.

    In a Ward Leonard system, a prime mover drives a direct current (DC) generator at a constant speed. The armature of the DC generator is connected directly to the armature of a DC motor. The DC motor drives the load equipment at an adjustable speed. The motor speed is adjusted by adjusting the output voltage of the generator using a rheostat to adjust the excitation current in the field winding. The motor field current is usually not adjusted, but the motor field is sometimes reduced to increase the speed above the base speed. The prime mover is usually an alternating current (AC) motor, but a DC motor or an engine might be used instead. To provide the DC field excitation power supply, Ward Leonard systems usually include an exciter generator that is driven by the prime mover.

    Although only technical specialists are likely to be familiar with Ward Leonard systems, many millions of people have ridden in elevators powered by Ward Leonard drives. From the 1920’s through the 1980’s most electrically driven elevators used Ward Leonard control and many systems remained in use at the beginning of the 21st century.

    Many variations of the Ward Leonard system have been implemented, but they have generally continued to be called Ward Leonard systems. H. Ward Leonard and many others have patented auxiliary control systems used to regulate the motor speed as required to automatically perform specific tasks such as controlling pump speed to regulate flow.

    Mechanical types of adjustable-speed drives and other electrical types continued to be used and new types developed after the Ward Leonard system was introduced. Electron tube types of DC motor controls began to be developed in the 1920’s but electronic controls didn’t seriously begin to displace the Ward Leonard system until thyristor controlled drives were developed in the late 1960’s. By the mid 1970’s, Ward Leonard drives were rapidly becoming obsolete, but the replacement of existing Ward Leonard drives has continued past the end of the 20th century.



    Note well the last paragraph: "... electronic controls didn’t seriously begin to displace the Ward Leonard system until thyristor controlled drives were developed in the late 1960’s."

    Greene's "Works in a Drawer" electronic drive (1949) predated this trend by nearly twenty years.

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    Vibration in my machine is minimal but its still there. More of a resonance really. Still you could do the balance a nickel trick if I could find a flat spot on the head where it nickel wouldnt roll away.

    Changing the drive out is not really an active project. If I ever find a wiad around from someone installing a VFD or something I might jump on that.

    For me electronics or mechanical will do. I work on both every day. The fewer the moving parts the better.

    But I really doubt I will ever change out the drive. Might have my spare MG unit repaired though, it has a shorted field winding. Or if I can get my friend to design a replacement power supply that emulates the MG set I might do that.

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    This has been a good discussion. Call me prejudiced but having a MG drive was second only to the lathe's mechanical condition when I decided to get a 10EE. It took years to find the right one but I stuck to my guns. The simplicity and robustness of the MG are what made the choice easy for me. I've used all versions of the Monarch DC drives and prefer the MG.

    At one former workplace with many 10EE lathes I recall much more frequent and lengthy service calls to the WiaD and Modular machines than to the old dumb MG versions. As Carla has noted, MG service is simple, quick and easy. It can be accomplished by personnel without electronic training. Service also involves only inexpensive and still available parts. Additionally, the MG starts up quickly. I'd wager the Navy specified MG units as long as they did for the same reasons.

    MG noise is a horror however, drives me nuts. My MG will go live in the same remote shelter that an air compressor and RPC have lived in for 25 years. As Peter noted, it's easy to do.

    I've had some discussions with several Electrical Engineers friends who specialize in power supply and DC control design about building a replacement for the MG set. It's definitely feasible but we all concluded it wouldn't be cost effective in low volume. There are good economics behind using a 3 phase motor and off the shelf VFD for retrofit on machines that need a new drive system.

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    "I've had some discussions with several Electrical Engineers friends who specialize in power supply and DC control design about building a replacement for the MG set."

    You know, if you convert the motor part of the M-G to a 12-wire configuration, you can operate an M-G 10EE from a single-phase source.

    You would have to make or install the equivalent of a H.A.S. static converter, but the practical information is available in the Steelman Electric Service user manual, and in the H.A. Steelman Letters of Patent.

    The Steelman static is one of the few which gives 100 percent of nameplate HP, when operated on single-phase power.

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    I believe that Steelman Patent is 2922942 of Jan 26, 1960 if someone wants to see it. It's available as a .tiff file from the Patent Office and requires a free reader.

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    This publication describes the practical aspects of the H.A.S. (H.A. Steelman) static converter. In particular, the required modification of a 9-wire motor to a 12-wire motor, so that the H.A.S. static may be implemented, is described. Some very useful tables are contained within this publication, and these may be used as a starting point for the specification of motor overload protection. In practical installations, separate protection will be required for the running winding (about 2/3 of the total current) and the starting/running winding (about 1/3 of the total current).

    http://www.capacitorconvertors.com/p...structions.pdf


    This Letters of Patent describes the H.A.S. static in the abstract, without providing guidance as to the actual schematic diagram of a converted machine or the selection of component values. Part of this is with reference to the above document, but most of this is from experimentation on the actual machine, not unlike the "tuning" process in an RPC.

    http://www.pat2pdf.org/patents/pat2922942.pdf

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    That looks interesting, I had seen you mention the H.A.S method in other posts. Wonder how difficult it would be to make the MG into 12 wire config. The converter itself dosnt seem hard to make.

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    "Wonder how difficult it would be to make the MG into 12 wire config."

    The "star point" needs to be isolated, and three wires need to be added where this point formerly was.

    These three wires should be labeled T10, T11 and T12, and there should be continuity between T10 and T7, T11 and T8, and T12 and T9.

    The wires at the "star point" are usually brazed, and the additional wires should be brazed as well.

    Sil-phos is the recommended braze.


    "The converter itself dosnt seem hard to make."

    Conceptually, it is not more difficult to make than a well-tuned RPC.

    The resulting machine needs only single-phase, yet it can easily be restored to its original, three-phase configuration.

    The starting means may be as I have previously described for 5 HP or less, or for more than 5 HP (see the RPC "Stickey").

    The running means can benefit from a power factor correcting capacitor (this was neither mentioned nor claimed by Steelman).

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    “Well, I'm ever so impressed with all the discussion of ultra-sophisticated electronic technology, and I can understand that it is indeed a fascinating and enjoyable field of experimentation for those who are into electronic engineering”

    To be clear, this is not experimentation or a Hobby for me, I have been working on robots for the last 25 years. My idea of using an analog VCU was simply a suggestion about a fairly common piece of industrial equipment that may “fill the bill” (I probably could have found a better description, I’ll see if I can)


    “.......but, from another point of view.....what of those folks who are just 'not electronic' as many of the people in this world are just 'not mechanical'?

    Its all well and good, for those who have the relevant knowledge and capability, to develop sophisticated solid-state electronic power systems, and, of course, technical advances are always desirable.....some become 'blind alleys', others go on to become 'state of the art', and ever so valuable.....possibly patentable or licensable, and worth some real money to their developers. I'm not saying anything at all against the on-going efforts of those who develop sophisticated electronic technology.....quite the opposite, in fact....more power to you, gentlemen, and may you develop better and better technology as time goes on....”


    You entrust your life to electronic equipment when you get into your car with airbags, antilock brakes, traction control, fly-by-wire throttle, engine management….
    I know precious few people who understand all those control systems yet use them everyday without question. Well designed electronic systems are extremely reliable.


    “Back to the original item, tho.......I can tell you from first-hand practical experience that the old Ward-Leonard drive with the motor-generator set is an optimal system for the actual needs of the little Monarch, given its use by machinists who are not electrical engineers, often under time pressure to produce close-tolerance high-finish parts, in the machine shop environment.”

    You bet, very reliable and very expensive to build today. I can’t agree more on the bombproof nature of an MG set…Now, as an end user who wants one of these gems that has been honed to perfection. Accept the fact that you are gonna have to suck it up and drop some coin for one, AND, expect to do it on a one by one basis because people are going to find less expensive ways to get the same thing done and you are not going to get any sort of “production run”.


    I don’t disagree with you, I think these old drives are wonderful, we are just stuck in a small market that is not going to get serviced unfortunately.

    “The MG set is easily understood and maintained by machinists and plant mechanics, an important difference not easily understood by those for whom sophisticated electronic systems are an 'open book'.”

    I put that squarely in the lack of acceptable troubleshooting documentation….it is the bane of my existence. I am a plain spoken person that spent many years in service where the option of going home doesn’t exist. When I write documentation for troubleshooting, I write like I have a plant manager breathing down my neck, its 3AM and I’m tired.


    "Aside from the obvious maintenance items of brushes, bearings, and contact tips, all of which will give years of reliable service before requiring renewal, the MG drive is a 'known quantity' in that its 'stable' and not 'finicky'."

    Yep

    “It may well be argued that the MG set is 'old technology' and 'obsolete'.....and, yes, thats a fair argument. It may well be argued that a new run of MG sets may not be 'cost effective', and that is certainly possible.....in fact, it may not be possible to have them built at all, at least to anywhere near the quality level of the Reliance drives of the 1950's.”

    Sadly, True



    “(in actual practice, our MG drive EE ran 'around the clock' at times, when we had large numbers of small parts to do under time pressure.......our MG drive EE, and the little Hendey gage lathe we had, were reliable in this respect.....our tube drive EE would run alright for sometimes a few weeks, sometimes only a day, before it would start 'hunting' under load, and require its potentiometers adjusted.

    Doubtless, the real underlying problem was one or more components which had become unstable from age, but we couldn't develop even a guess as to which components might have been the problem, and didn't have time to fool with the machine, as we had to get the work out. This, of course, is a problem associated with being a little 'hole-in-the-wall sub-contract shop, as compared, say, to being the experimental shop of a well-financed firm where time and money are more readily available. We had no choice but to 'get the work out', and reliable equipment was a necessity)

    The electronic drives, even tho designed for a similar service, and intended to be adequately capable of handling the hundreds of thousands of intermittent loadings imposed by the starting and braking of the spindle motor, do seem to have their inherent flaw, that of component degradation over time. This is quite understandable, and doubtless inevitable, given the sheer number of components which make up the electronic drive systems, and the wide range of loading cycles they experience in normal use.”


    We fight degradation of components all the time, our primary nemesis is the electrolytic cap, age and heat can really take a toll on them.

    That said, a spot weld robot with a dull normal life of 8 years is going to do about 2-3 million production cycles and about 40 to 60 million welds. A robot is a reciprocating machine therefore it is designed to withstand heavy loads imposed by acceleration, gravity, over payload…et al. a typical major axis servo amp is going to deliver ~50 amps continuous with typical acceleration currents of 90 to 100 amps….perhaps 10-15 times per cycle. A small auto plant will have hundreds of robots with at least 6 amps per robot, that’s thousands of amps; if they weren’t reliable; we wouldn’t be in business more than a week.
    I don’t think you understand just how tough and reliable modern servo drives are.


    My heart goes out to the small job shop, I grew up in a family with a small business and I go way out of my way to use small businesses first when I buy things, the road for the small business today is long and tough.

    I love the classic nature of these machines and I hear people saying that they are worth your best effort when making them run….our best effort may very well be a cost effective combination of the very best modern electronics and motor control technology applied to a machine that is actually worthy of the effort.
    I can’t agree more with many of your points; I just think we need to keep an open mind as to alternatives that might be a win-win on price and reliability.

    Remember,

    “Must Run…ALWAYS”



    Cheers,
    Sean

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    Quote Originally Posted by lennoncs View Post
    “It may well be argued that the MG set is 'old technology' and 'obsolete'.....and, yes, thats a fair argument. It may well be argued that a new run of MG sets may not be 'cost effective', and that is certainly possible.....in fact, it may not be possible to have them built at all, at least to anywhere near the quality level of the Reliance drives of the 1950's.”

    Sadly, True
    I dont know if I would say that. This is related to the "things arnt made like they used to". When in reality people are not willing to pay the cost to have the quality of what they used to be. And a lot of things are much better now as well.

    I am sure you could get reliance to build you a new MG set. Probably cost a bit the equivalent 1940 dollars to get one made today. Better bet is to have a old MG completely gone through.

    Anyone know how much a MG set cost back then?


    Peter, where is that sticky you were referring to?

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    Macona,
    agreed,

    materials are much better than before; but we are in this "cost control" death spiral.

    We suppliers are sure feeling that pinch all the time.



    Sean

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    The WiaD and Modular are electronic simulations of the Ward Leonard drive.

    The speed pot performs the same function in all three, it:

    1) increases the armature voltage, while maintaining the field voltage at maximum,

    2) reaches the half-way point, also called the crossover point, where the armature voltage is maximum and the field voltage is maximum, and

    3) decreases the field voltage, while maintaining the armature voltage at maximum.

    Areas (1) up to (2) is a constant torque mode (also a variable horsepower mode).

    Areas (2) up to (3) is a constant horsepower mode (also a variable torque mode).

    The armature regulator of the WiaD and Modular (two C16Js) perform the same function as the dc generator's field circuit of the Ward Leonard drive: in response to the speed pot, the armature voltage of the spindle motor is increased or decreased.

    The field regulator of the WiaD (two 3C23s) and the Modular (one C3J, plus a "free-wheeling" diode, REC3) perform the same function as the spindle motor's field circuit of the Ward Leonard drive: in response to the speed pot, the field voltage of the spindle motor is increased or decreased.

    The Ward Leonard, WiaD and Modular drives all have a DC Panel which, of course, performs reversing of the armature (the field, having a much higher inductance, cannot be as easily reversed), but also performs field acceleration when changing speeds, and performs deceleration when braking. Loss of field is also detected, and will shut down the machine to prevent a spindle motor runaway (this function is not provided in the Ward Leonard drive because loss of the exciter, which is the source of the field voltages, also causes loss of the armature voltage, and it is the loss of the field voltage combined with the presence of the armature voltage which causes the runaway).

    Where the WiaD and Modular appear to be different, they are really quite similar, except: the WiaD performs all control functions at low levels, using amplifiers to provide the higher levels necessary for control of the armature and field regulators, while the Modular performs all control functions at high levels, using attenuators to provide the lower levels necessary for control of the armature and field regulators. These control voltages all meet at the thyratron grid control circuits, which are similar between the two drives.

    An important function in the Modular drive not found in the WiaD drive is the module itself, whereby removing the module removes most of the electronics (and most of the components which are reasonably expected to be "flakey") while placing the drive in a known state: maximum armature voltage and about one-half field voltage, and which causes the spindle motor to revolve at about twice its "base speed". This is a very important diagnostic tool, and one which should be understood and used.

    The next revision of 10EE drive was the armature regeneration, or SCR drive, also called a "Monarch Sidney" drive. This drive eliminates all the electromechanical components and simulates the reversing contactors and the thyratrons with SCRs. However functions which are very simple with electromechanical components can become quite complicated using pure electronics, and this drive has hundreds of resistors, capacitors, transistors and small-scale integrated circuits (some of these being quite sophisticated, such as analog multipliers), and is quite impossible to troubleshoot this drive without special test fixtures.

    Reliability issues in WiaD and Modular drives, when compared to the Ward Leonard drive, can be traced to components which appear to be good, or are good under a restricted set of operational conditions. Flakey diodes in the Modular drive are prime offenders. Thankfully, the "small signal" vacuum tubes in the WiaD are usually not the source of drive troubles, rather insulation breakdown in the grid transformers appear to be the prime offenders, yet these grid transformers are also present in the Modular.

  14. #34
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    Hi, Sean,

    Re your comment.....
    ----------------
    You entrust your life to electronic equipment when you get into your car with airbags, antilock brakes, traction control, fly-by-wire throttle, engine management….
    I know precious few people who understand all those control systems yet use them everyday without question. Well designed electronic systems are extremely reliable.
    -----------------

    Well, I'm rather emphatically not one of that 'precious few'. I've never driven, or even ridden in, a vehicle which uses any of that technology, and am not about to start now. Yes, I'm that strange life-form, a 'technological atavist'.....I tend to 'pick and choose' the generations of technology which I'll have in my life.

    Our small vehicle fleet includes a pair of Land-Rovers, of 1966 and 1969 vintage, ex-British military, which are everyday transport. I can understand and maintain every component and system on these, and have a fair stock of spares, to, hopefully, keep them in service for some time to come.

    My own 'pet car' for many years was a 140 model Jaguar, which ran reliably, but I decided to sell it after it was very nearly the victim of car thieves a couple of times......it had become 'collectible' or some such thing, you see, and there are nut case collectors with much more money than common sense, who will pay absurd amounts of money for such cars, hence their desirability to those who steal them, and those who 'restore' and re-number them.

    At present, I'm working on the vehicle which will become my 'everyday use' car, a common or garden variety '34 model Plymouth sedan, to which I'm fitting-up a '50's Dodge military M37 engine. As chance would have it, the car was owned by a local elderly couple, who passed away a few years ago, and kept in perfectly preserved condition, never pranged or allowed to rust, so, with the military engine, it should run utterly reliably for many years to come......its rather snail-like, of course, compared to any Jaguar, but, well, I just don't need to run as fast as I once did.....something about not being as young as once was.

    Another vehicle in our little fleet is a '86 Plymouth sedan, the car which was issued to my partner as her 'company car' when it was new. She had it scrupulously maintained by the vehicle shop at work (she was in charge of public-safety commo for our City here for many years, and took retirement two years ago), and we bought it at auction when it was 'retired' as 'over age' for active-duty vehicles. Even tho its been 'babied' ever so carefully all its life, its basically a 'mechanical joke' as quality goes, so we have it primarily cos of her 'sentimental attachment', and use it very gently.

    Would I consider a 'fly-by-wire' car?......hardly.....the computer on which I'm running this comment 'glitches' every little while, and has to go through a 're-start' procedure, or I have to have someone who knows computers 're-set some parameters' or whatever it is.....like the famous 'blonde joke' person who can barely operate a car, I'm pretty much intimidated by the technicalities of the computer.

    Could I even imagine having a car controlled by a computer, or being a passenger on an aircraft controlled by a computer after some first-hand experience with the simplest sort of computer, the one I'm using now?

    The road we live on goes from 400 ft. elevation to a bit over 4000 ft. in twenty-ish miles, with quite a few twisty tight turns......we see all too many of these fancy new cars which go off the road, either cos their computers failed, or they were driven by people who didn't understand tire adhesion, brake fade, and suchlike....in short, maybe they likely to have been lulled into a false sense of security, or some such, by their new 'magic' vehicles.....it might be that they believed the advertising, and so substituted an unrealistic expectation of the capabilities of their car's computer technology for ordinary plain common sense, not a very good idea considering the mass/velocities involved.

    Sean, I'm very impressed with your knowledge and ability......many of us just aren't able to work on your level, sad to say.

    cheers

    Carla

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    "Peter, where is that sticky you were referring to?"

    http://www.practicalmachinist.com/vb...9&postcount=47

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    Default "they jus don't build'm like they used to....thank god!

    I have to chime in a bit.....one of the very good reasons that modern cars, machine tools, etc, are considered inferior is a failure to compare apples to apples. While I am hardly enamored of many modern contrivances, this thread is a bit misleading. Try comparing a '69VW bug to (for example) a '08 Honda fit. They cost about the same in adjusted $$ and the Honda goes farther faster infinitely more safely than the bug. You can expect it to go 200k+ miles without a rebuild (because it was put together with modern tolerances using modern machinery and materials) and along the way it will produce orders of magnitude less CO, NOx etc. They don't build them like they used to because we have learned a LOT about how to do it better. Don't get me wrong, I love old machinery but this, this is absurd. You cannot buy an new MG set for your lathe today because it is, in modern terms, a bad design. Using the additional energy required to do mechanical rectification to control 5kW in this day and age is absurd. Make no mistake, it was a beautiful design at the time......but we can achieve the same result today for a much smaller investment in materials, time and energy (both the energy to manufacture and operate).
    I keep an old MG TC around (my mother bought it new in college) but I would not dream of driving it everyday, if for no other reason than the fact that its tailpipe emissions are at least 10 times (and probably more) worse than a modern electronically controlled fuel injected vehicle (and that’s when its in tune which with old SU cabs is only once in a while).
    Several people on this site work on systems that depend VERY heavily on electronics which must work right every single time (OK, maybe “only” 10 sigma) or people die. One of the reasons we use electronics so heavily is that they are ridiculously reliable compared to mechanical devices, they are just much much harder to cludge in your back yard. When was the last time you heard of an airliner crashing from mechanical failure or flying into a cumulo-granite cloud because they weren’t where they thought they were…..now think back maybe 30 years to when it was MUCH more common even though there were many fewer airliners. I love celestial navigation as an elegant and useful way to find out where I am, but I’m not about to drive a boat into a strange harbor in the middle of a stormy night without turning on the GPS!
    So, while I agree that things like an EE are works of industrial art and should be used and preserved, let us not try and pretend that nothing has improved since early ’49!
    Cheers,
    Steve

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    "You cannot buy an new MG set for your lathe today because it is, in modern terms, a bad design. Using the additional energy required to do mechanical rectification to control 5kW in this day and age is absurd. Make no mistake, it was a beautiful design at the time......but we can achieve the same result today for a much smaller investment in materials, time and energy (both the energy to manufacture and operate)."

    The whole point is the later drives, after the Modular, were NOT improvements, but were intended to take advantage of a lower "first cost", possibly at the expense of a higher "ongoing cost".

    Just moving the costs from the capital side of the ledger to the expense side of the ledger is NOT good design, although it may look good to the "suits".

    In the end, you have to ask the operators: can your VFD drive (or whatever) perform every operation as well as, or better than the WiaD drive (or whatever) in every respect.

    I don't have any magic answers, but I strongly sense that keeping a M-G, WiaD or Modular in operation for as long as one has the patience and the pocket-book, is better than a replacement.

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    Quote Originally Posted by peterh5322 View Post
    In the end, you have to ask the operators: can your VFD drive (or whatever) perform every operation as well as, or better than the WiaD drive (or whatever) in every respect.

    I don't have any magic answers, but I strongly sense that keeping a M-G, WiaD or Modular in operation for as long as one has the patience and the pocket-book, is better than a replacement.
    Time for me to chime in too...

    You make two statements above. The first one has a question and is easy to answer. Absolutely better in every respect, with more capabilities in fact. But that's not with a VFD.

    To the second statement (and please note that I'm saying all this respectfully) I strongly disagree.

    We seem to be assuming that a VFD and an AC induction motor are the option as a replacement. Clearly they have been used, and with acceptable results, but they are not on par with anything that came in a monarch (I agree with you on that).

    The fact is, VFD is a cludge job that we can hack in our garages for a reasonable amount of money. There is much better available.

    Look at lathes available today, high end ones that are comparable in quality to the Monarchs of yesteryear (yes all are CNC), not a VFD in the lot. Every spindle is AC servo controlled. You have full torque over the whole RPM range, spindle position knowledge, and often spindle position control. And they can start and stop so quickly it makes a stock EE look pedestrian. Oh, and they make almost no noise, their electrical efficiency is thru the roof, and they are a fraction of the physical size.

    Cheap? Certainly not, but neither are EEs...

    Just my two bits.

    I'm very enamored with the drives that are available in the EE, but it's doing ourselves an injustice to compare them to a VFD and assume that's the modern alternative...


    ciao

    lino

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    I'm interested in the servo motor idea. I've never thought of them for a drive replacement, just know that they shove our little CNC router back and forth. Seems an excellent case of using a modern technology to supplant an old one. I know nothing of the systems sean is referring to, but my experiences with small servos and drivers doesn't give me the idea they are way above most people's heads.

    In the matter of drive replacements, it seems the sensorless vector VFD's and an AC motor driving through the the backgear box are probably the real practical solution. I would think that if a better system was available at any affordable level, Monarch themselves would be using it. If they can't do it profitably as a supplier of new and rebuilt machines, I doubt any small run of whatever is conceived is a financially viable venture. Simply put, there is no market to serve. I would think that if keeping these machines was so valuable to the companies that originally afforded them, then there wouldn't be many of us with one in the garage or basement to even be worrying about this.

    And if it helps make it any clearer, I am an MG set fan, but more due to fear of component prices than complication.

    I put that squarely in the lack of acceptable troubleshooting documentation
    Good point. It seems that more than one lathe here was found dead and brought back. But there sure are a lot of questions here that point out that the documentation is not available.

    OK, I gotta ask, even though it's probably semantics and nit picking, but carla, do you really live off a special twenty mile stretch of road that's causing catastrophic electronic failures in automobiles? Idiot drivers I can believe, but a significant number of car computers going up in smoke...

    I would love to see some more suggestions on the servo motor idea, like part numbers and costs, seems an interesting path still,

    Rob

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    As someone who has a VFD 5hp conversion in my 10EE I'm curious as to the differience in performance between the two machines. On paper the base rpm of the DC motor of 1140rpm gives that unit 23 lbsft torque compared to the 15 lbsft of the 1750 rpm AC motor. That could help with those slow speeds like threading where you don't need backgear for smaller sizes. That advantage ends at 2250 rpm spindle speed on a 4K rpm setup. Is the DC smoother than a 3phase at all rpms, does it surge at low 50 rpm or what. Having never run the Wida, or MG unit I've nothing to compare the VFD to.

    A 7.5 hp AC VFD unit would equal the DC drive in torque up to 1460 spindle speed, and exceed it thereafter, guess that is why Monarch chooses to go with that size as a replacment.


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