PWM Drive for DC Motor
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    Default PWM Drive for DC Motor

    Probably still a little premature to share, but I'm excited to have been getting some time in on the lathe restoration lately. Project is 1943 10EE that I tore apart almost 15 years ago and am just now getting back to operational. Still lots of paint stripping / repaint in the future (tailstock and all the covers). But, at this point, I don't care what it all looks like. I just want a functioning lathe.

    Anyway, part of the restoration is a drive conversion to modern PWM drive of my own design. Developed it years ago for a 3-phase PMAC motor but put the hooks into the design such that it would be able to drive the brushed DC motor in the 10EE when time came. That time is now. Hopefully finish off the power wiring this weekend and can get to work on software and controls.

    Input power is 240VAC single phase. Off the shelf 250VDC, 3kW power supply feeds the inverter. 2 legs of the 3-phase drive make up a full h-bridge to drive armature in either direction. 3rd leg feeds the field. When all done, old-school DC motor performance capable of running full-tilt directly off of single phase power





    Last edited by Kezorm; 05-07-2021 at 06:37 AM.

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    pretty cool stuff there. Would like to see how it turns out. Mine is a 43' as well. Don

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    Quote Originally Posted by Kezorm View Post

    PWM drive of my own design.
    Cool. I did a PWM drive design on my day job about 25 years ago, 165V 30A, 3 phase brushless DC. Inductive kickback and self generation were a problem.
    I would love to see your schematic.

    CarlBoyd

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    Quote Originally Posted by CarlBoyd View Post
    Cool. I did a PWM drive design on my day job about 25 years ago, 165V 30A, 3 phase brushless DC. Inductive kickback and self generation were a problem.
    I would love to see your schematic.

    CarlBoyd
    Nothing too exciting in the inverter. This is personal project started about 5 years back for PMAC motor. I've done several other motor drives, larger and smaller, over past 15+ years as part of day job. Nothing out there exactly what I needed, so figure I'd spin my own. Also knew I'd want something for the 10EE eventually as I scrapped the motor-generator gear 15 years ago but knew that I wanted to keep DC brushed motor. The 3HP large frame motor is pretty killer in many regards. Maybe not the most efficient thing in the world, but unbelievably smooth with gobs of inertia.

    The inverter is 100% design by overkill. No intent to make it a sell-able product. Plan has always been to make everything open source hardware / software, but I'm still hesitant about liability aspects. As you know, 250VDC is nothing to mess around with. I'd be glad to help individuals pursue a build based on the design, but I have absolutely zero interest in everything that would go into trying to produce and sell it.

    Anyway, here's the inverter schematic (Schematic - Monarch Motor Power). USE AT YOUR OWN RISK. Everything design by overkill. No attempt whatsoever to optimize cost (inverter is probably around $150 BOM cost at QTY 1). Use off the shelf, oversized IGBT module. Hall effect current sense to make for easy sampling and isolation. Current sense on all 3 legs so that I can use in this Brushed DC application (2 legs for armature and 1 for field). Off the shelf isolated regulators to generate the low voltage logic supply. All the controls are completely isolated electrically from the motor bus voltage. This makes it easy to hook up to the microcontroller for programming, debugging, etc. as the necessary isolation is already baked into the design. Logic board is separate, connected through P1 in middle of page.

    TB1 in upper left is DC supply input. TB2 in lower right is 3 phase (and ground) motor output. Everything rated to handle 400VDC bus. Current sense can measure +-40A. I expect the drive would be thermally good for up to about about 5kW. Note that this is 2 quadrant drive, not 4. But, should be all that's needed for 10EE service. (although, theoretically, 4 quadrant would be possible if the supply had ability to sink current)

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    Carl, this looks really interesting. Could you provide the native KiCad project file?

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    Did you paint it? What paint & color if so?

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    Quote Originally Posted by Kezorm View Post
    Nothing too exciting in the inverter. This is personal project started about 5 years back for PMAC motor. I've done several other motor drives, larger and smaller, over past 15+ years as part of day job. Nothing out there exactly what I needed, so figure I'd spin my own. Also knew I'd want something for the 10EE eventually as I scrapped the motor-generator gear 15 years ago but knew that I wanted to keep DC brushed motor. The 3HP large frame motor is pretty killer in many regards. Maybe not the most efficient thing in the world, but unbelievably smooth with gobs of inertia.

    The inverter is 100% design by overkill. No intent to make it a sell-able product. Plan has always been to make everything open source hardware / software, but I'm still hesitant about liability aspects. As you know, 250VDC is nothing to mess around with. I'd be glad to help individuals pursue a build based on the design, but I have absolutely zero interest in everything that would go into trying to produce and sell it.

    Anyway, here's the inverter schematic (Schematic - Monarch Motor Power). USE AT YOUR OWN RISK. Everything design by overkill. No attempt whatsoever to optimize cost (inverter is probably around $150 BOM cost at QTY 1). Use off the shelf, oversized IGBT module. Hall effect current sense to make for easy sampling and isolation. Current sense on all 3 legs so that I can use in this Brushed DC application (2 legs for armature and 1 for field). Off the shelf isolated regulators to generate the low voltage logic supply. All the controls are completely isolated electrically from the motor bus voltage. This makes it easy to hook up to the microcontroller for programming, debugging, etc. as the necessary isolation is already baked into the design. Logic board is separate, connected through P1 in middle of page.

    TB1 in upper left is DC supply input. TB2 in lower right is 3 phase (and ground) motor output. Everything rated to handle 400VDC bus. Current sense can measure +-40A. I expect the drive would be thermally good for up to about about 5kW. Note that this is 2 quadrant drive, not 4. But, should be all that's needed for 10EE service. (although, theoretically, 4 quadrant would be possible if the supply had ability to sink current)
    I'm sure it is nice work, and would love to have a schematic for file, even though I'm about done with 10EE, what with SSD's and big fat chokes just doing the do,

    Off script and messing with my HBX-360-BC far more often, these days.

    Google-everything is hard-blocked here. No fle for me!

    My email is [email protected] if you are in the mood.

    Opening of ancient kimonos as we are?

    Before side-tracked to the Eurotherm/Parker "rude-bugger" Thyristor-class noisemakers?

    I had started out with the idea to do-up an ultralinear, of the sort I wudda run an Old Skewl Bill Marconi HF coms link with. Or powered our AN/FPS-35 whole species at a go bird-barbecuer out a Montauk Point. NORAD, Northrop-Page, & Dominant IRC carrier (C&W retiree). Not limited to HAM tranceiver power class! At all.

    Hot? Surely!

    Wasteful? Dambetcha!

    Smooth? Tenth of a percent ripple do yah?

    And then? I bought the second 10EE.

    And that tookup at least HALF the SPACE the monster wudda needed!

    The HBX-360-BC took the OTHER half.

    Analog tech was gooooooodddddddd.

    Just not necessarily smaaaaaaaalllllll.

    You'd have to know the AN/FPS-35?

    Or maybe just trans-oceanic Forward Propagation Tropospheric Scatter?

    I did say "wasteful"? Blew the beam off to some other galaxy and carried the traffic on the NOISE, basically!


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    Quote Originally Posted by Briney Eye View Post
    Carl, this looks really interesting. Could you provide the native KiCad project file?
    I'm not quite ready to release everything into the wild yet, couple bugs in the current revision that I haven't gotten to fixing yet. But, I would be glad to share individually and help someone pursue their own build if desired. I have several more bare PCBs of each of the boards would be glad to part with for few bucks (mainly just cover shipping). As mentioned, a couple mistakes so they need a little rework, but not too bad.

    Do you have account at GitLab? Not ready to make totally public yet, but can give access to individuals. Or, PM me an email or something and I can zip up files to send.

    Greg

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    Some renders and actual pictures of the inverter. Size of power board is 4.5" x 6.75". IGBT module on back side of board mounted to aluminum heatsink. Logic board is really just main microcontroller (Microchip SAME51) and a bunch of expansion ports for field I/O. I have two I/O boards designed so far. Both 24VDC industrial digital input boards (EN 61131-2 type 1 inputs). One board is 5 channel digital input direct to microcontroller + USB serial port. This is intended for higher speed inputs like quadrature encoder. Also a STOP input that can be routed direct to the PWM peripheral as hard fault (i.e. hardware shutdown all PWM). 2nd board is 8-channel digital input, interface to microcontroller through SPI bus. Logic board is completely isolated from power. I/O boards all have functional isolation from the logic board.

    Greg










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    Quote Originally Posted by TBJK View Post
    Did you paint it? What paint & color if so?
    Yes, repainted with POR15 "Hardnose" paint (think it's called "2K URETHANE" now). Pretty sure light gray on the base. I honestly forget what state the top half is in - was done over 10 years ago. I thought I just just gotten it to primer, but maybe I put on the dark gray top coat. No idea why I went different color. Think maybe I was planning to put another coat of the dark gray on base to match the top. Sad I can't actually remember. Regardless, good enough for now. The covers and tail housing are still as I bought the lathe, coated in gods know how many layers mostly dark blue. Some day I'll maybe get around to cosmetics, but for now I just want a working lathe, patchwork color scheme be damned.

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    Quote Originally Posted by thermite View Post
    Google-everything is hard-blocked here. No fle for me!
    No google?! That's hardcore, man. I won't claim to be fan of the Google either, but damn. Can you see pictures? They are linked from google... (I assume everyone else can see pictures and I don't have some stupid mistake with permissions?)

    Will send schematic by email. Let me know if want more details. As mentioned previously, not quite ready to completely release everything to the wild. But, glad to go deeper on individual basis for now.

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    I can see that this is not your first rodeo, and you either have first-class soldering skills or contracted out the assembly. Well done.

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    Quote Originally Posted by Briney Eye View Post
    I can see that this is not your first rodeo, and you either have first-class soldering skills or contracted out the assembly. Well done.
    PCB assembly is all hand done in home lab. SMT down to 0402 is easy once you learn the trick. Paste stencils are cheap (<$10). Squeegee on paste with old credit card, hand place components with tweezers (good stereo scope is big help, but not required), pop in converted toaster oven, done.

    Greg

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    Quote Originally Posted by Kezorm View Post
    No google?! That's hardcore, man. I won't claim to be fan of the Google either, but damn. Can you see pictures? They are linked from google... (I assume everyone else can see pictures and I don't have some stupid mistake with permissions?)

    Will send schematic by email. Let me know if want more details. As mentioned previously, not quite ready to completely release everything to the wild. But, glad to go deeper on individual basis for now.
    No fotos. Black screen. Got the schematic by email, thanks.

    PWM is no stranger, nor PCM or PAM. Signaling more often than power. Telco thing.

    One of my KB-Penta drives is PWM, but it's only running a tiny Bodine DC gearmotor.

    IIRC, Reliance introduced the first-generation of 3-or more of "Rectified Power Motor" AKA "RPM" series right around the time "original" Monarch Machine Tool entity ceased making any kind of lathe at all and motored off to Courtland, NY to make drillpresses and mills?

    So "AFAIK" NONE of the DC motors a 10EE used were "inverter duty".

    Meanwhile .. (John) Shackelton System Development => Eurotherm => Parker "SSD" calls for a "ripple filter" in this type of service.

    Even Reliance RPM III - purpose-built FOR Rectified Power - calls for a ripple-filter when run off an inverter for all Voltage windings ABOVE 180 VDC. I think I have six RPM III and every one of them is "heavy-bugger" 180 VDC wound! For that very reason! Plus not needing a boost transformer.

    Now .. my KB PWM drive is "here" because the DC gearmotor it drives is a 130 VDC unit. PWM as KB do it can deliver 130 VDC off 120 VAC wall outlet - mine are 123 VAC anyway. The current is low enough the choke I use for a ripple filter is a tiny Coilcraft.

    But that's a Permanent Magnet motor. No Field coils nor Field current supply, no Field Weakened range. No "Field Regulator" circuit, more's the pity.

    So it JFW right outta the single-phase wall, no boost transformer and only a modest inserted inductance to clean-up the switching bleeding edges.

    So OK . you are running THIS PWM creature off 3-Phase input, say 240 VAC leg-to-leg?

    With the way KB do it, you should be able to sustain 260 maybe 270 VDC out?

    Right about the normal range for a 3 HP large frame as Monarch actually ran it, Eg: "Crossover" to Field Weakening @ 230 VDC, but as much as 300 VDC on-tap for regulating well once deep into the Field Weakened range.

    It will be interesitng to see how well this performs on the 'scope, "real world" use, and how smoothly.

    There is a LOT of "stuff" in a Four Quadrant SSD drive. Waaaay more than a "4Q' KB-Penta, what with the OP Amps, reference sources for the IR loop or tachogenerator feedback, ramp-rate adjust, permissable over-current, responsiveness curves, and sensitivity shaping, 8 SCR firing trigger inductors, $80 MOV, etc. etc...

    A LOT of stuff!!!

    Over a thousand bucks, brand-new. A Beal/BICL D510 actually cost MORE.. but didn't work very well if it's El Cheapo primitive two active-Diode only SCR bridge even survived itself for very long.

    And they didn't always. PIV was waay too low for an arcy-sparky contactor-reversing 1Q drive bing run at right about half the PIV rating before it ever even drew an arc.

    "Let's see how this goes in actual use .."

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    Quote Originally Posted by thermite View Post
    So OK . you are running THIS PWM creature off 3-Phase input, say 240 VAC leg-to-leg?
    This PWM creature running off of 240VAC single phase. DC power comes from off the shelf 250VDC, 3kW supply - https://www.meanwell.com/Upload/PDF/...-3000-SPEC.PDF . Should be just enough for 3HP mechanical. Doubt I'll ever take it anywhere near 3HP in my work. But, if need be, can always parallel another 3kW supply. Or, I can swap in a 380VDC, 5kW supply that I built years back (also 240VAC single phase input).

    Quote Originally Posted by thermite View Post
    It will be interesitng to see how well this performs on the 'scope, "real world" use, and how smoothly.
    At 8kHz switching frequency, the motor won't know it different from straight DC. Not worried about inverter duty motor. Plenty of thermal headroom in the design, so no need to go excessive on switching frequency / edge rates.

    Ignoring time, all in BOM cost is easily under $1000 (including DC supply, filters, inverter, breakers, wire, etc.)

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    Quote Originally Posted by Kezorm View Post
    This PWM creature running off of 240VAC single phase. DC power comes from off the shelf 250VDC, 3kW supply
    That's "appears to be" really close.

    The "large frame" 3 HP (nominal) is only at 3.5 KW calculated even hot-rodded to around 4.6 motor HP. Problem is a "Type T" pays for smooth in lower conversion efficiency. electrical energy to mechanical energy. About 73%, at its sweet spot.

    Less when pushed out of its best place on the curve. So the 380VDC, 5kW supply would be the one to use - dialed-down a skosh, but running under-stressed.

    Not for ripping chip harder. "Broken record" playing again on that.
    For holding stability better in the Field Weakened range... where there IS NO comparable sophisticated outer-current-loop "Field Regulator" doing the do. SSD has those on-PCB or on option-card for their over ten HP 3-Phase-only DC drives. Most major vendors do.

    SSD even USED TO HAVE a single-phase one down in the small-potatoes sub 10 HP range. I have the manual. It worked with the immediate predecessor to the 514C-XX drives. But that was mebbe 20 years back? I've only ever seen ONE hit the used market. Looked beat, "untested". over-priced. I gave it a miss.

    Mind the ABSENCE of them in the market supports what I've seen "real life".

    So long as there is enough reserve Armature power, the built-in IR sensors JFDI in the Armature supply alone. Same again with the tacho. We've several. Too little gain to bother.

    At 8kHz switching frequency, the motor won't know it different from straight DC.
    That's why i asked about the 'scope shot.

    Telco or "puter guy hears "PWM" we expect square-waves, overshoot, ringing, the whole nine yards off a chopper, DC fed.

    SCR at least is only bludgeoning a 120 Hz half-Sine wave for seed-corn. Classical Yaskawa/Magnetek "Quiet Elevator" LC filter uses just under 400 MFD for the 10 HP "reference circuit" on those.

    I acquired the caps. 460 VAC rated from an HVAC house. Didn't make enough difference vs the raw choke that I felt like adding any short-life components. So I didn't leave them in the "working" model once it came off the bench.

    The choke does what the schematic shows it does. "eats evil" before it hits the motor.

    Testing was done with the power unit on the bench, long-wired to the 10EE & motor.

    The amusing part is that the accell & decell "growl" had moved OUT of the motor and INTO the choke.

    So all the "drama" was taking place on the BENCH as if there were a coupla dogs arguing over a bone over the other side of the room!



    Result was really quiet over at the LATHE, though!



    Once in the belly of the 10EE, the casting attentuated the growl nicely, but it was a lot closer, and the growl was located right below yer crotch! "HUNGRY" lathe syndrome, sundng as if coming from the cutting-tool rather than the motor...but hunger for chips, not "people food". Or so I freakin' HOPE! These old "vampires" have sucked more money & blood out of the room than exotic go-fast motorcars, past few years!



    By contrast, as Beel/BICL drive, motor in-circuit, was cranking about 130 V of AC component trying to find a path to a victim.

    SSD it was only 56 V AC component, dropped to a 6V ripple once the big Lenze swinging choke was inserted.

    Dunno where you expect 16,000 leading & trailing edges to be attentuated if the motor itself is the only device doing the integrating? Mind at the higher freq and shorter, more evenly distributed, "OFF" time gaps, you would NOT need the 20 MILLI-Henry the 120 Hz stuff needs. Smaller & lighter 20 MICRO Henry maybe?

    It ain't the thermals. Probably won't "flute" the bearings, either.
    It's the piercing effect on the old insulation.

    Those Type T are a Royal bitch kitty to rewind, charged for accordingly. Another reason I have 100% spares!



    Ignoring time, all in BOM cost is easily under $1000 (including DC supply, filters, inverter, breakers, wire, etc.)
    That includes the DC PSU? Not bad. But how well does it brake?

    Seems about $500 to $1000 saving even if the time is for free and not for fee?

    But the SSD approach at that price all has full factory warranty and a replacement - if ever one even has to do such - is to simply duplicate the DIP and BCD switch settings, bolt-in, and do a bit of screwdriver tuning.

    IOW. with all commodity parts, notes as to the commissioning switch and trimpot settings, no DIY components, one could even hire it serviced by a sranger.

    You can do notes for making your drive jsut as easy, but one major part is NOT "off the shelf". Your core PCB.

    Not YET, anyway.

    Plans? Well what Jonathan Esar discovered is the market is too small, each drive lasts a long time so there is no replacement market, and yet the installation and service cost was too high for the revenue as could be derived. He also had the extra challenge of being a Canadian company with most of the customers in the USA.

    That put a hurt onto shipping units back and forth for service, and service was needed, given they had to be installed and integrated.

    If we have collectively learned ANYTHING it is that preserving and restoring "whichever" drive came from the FACTORY, any given era of 10EE, is nearly always the least cost and least hassle.

    - MG's are mostly commutator clean-up, new brushes and bearings.

    - WiaD and modular, Tim has drop-in solid-state replacement for the scarce and expensive Thyristor tubes. That has become a "game changer" especially for the Modular 10EE.

    - SSD's exist for single phase. many more 3-Phase-only DC drives can work, too, if all one has - or can FIND, used - is the DC motor.

    - Just recently, we even discovered that the unicorn-rare Sundstrand has a current model drop-in-mostly as well.

    -VFD's "work". Really good ones as the factory uses can work very well.

    Your drive is one more choice?

    I'm good with that!

    The more choices we have? The fewer 10EE risk getting scrapped!

    We still need someone to try a steam turbine?

    I think we had a steam recip and a Diesel arredy?

    Pleeeeeeeeeez.. no 2-stroke weed-wacker motors?

    Last edited by thermite; 05-10-2021 at 04:08 AM.

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    Quote Originally Posted by thermite View Post
    That includes the DC PSU? Not bad. But how well does it brake?
    Is 2-quadrant drive. Well, technically it's not the inverter that makes it "only" 2 quadrant. The DC power supply is the limitation, can't put it back onto the line. So, will need braking resistor to get better than coast to stop.

    Quote Originally Posted by thermite View Post
    Plans?
    None beyond my own use. This is fun exercise for me. No desire to manufacture / sell / support. As you say, no market. I'll be glad to help others investigate the design, but that's as far as I go. I'll gladly share PCB design files, so even the PCB could be considered "off-the-shelf" these days. For example, I paid $72 for QTY 10 of the power board ($7.20 each). Delivery in <2 weeks from China. Gone are the days of photo resist and ferric chloride. It's gotten so easy that I rarely even breadboard anymore. Easier and cheap enough to just whip up quick proto PCB.

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    Quote Originally Posted by Kezorm View Post
    Gone are the days of photo resist and ferric chloride. It's gotten so easy that I rarely even breadboard anymore. Easier and cheap enough to just whip up quick proto PCB.
    Yes, for many years now. I never missed etching or wire wrap. Where I retired from had a world-class PCB shop that charged projects world-class prices. They died gradually, then suddenly. Jobs started going to Shop Overflow, then they even gave up on that and started letting us send things out directly over the InterWeb, and they were bled dry. Our huge world-class machine shops suffered the same fate. Peace is hell on government labs. The Union didn't help, either. The rows of 10EE's, CNC's, EDM's and all the other machines up through huge oil patch-size and vertical-axis lathes went to Reclamation. I hope they went to good homes, and not scrap.

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    Quote Originally Posted by Kezorm View Post
    Delivery in <2 weeks from China.
    Hell, Shenzen can put a design into volume production, snazzy packaging and full-colour brochure, in half a day, be filling sea freight containers by the end of the same week!

    Cousins we usta take unworn and out of style clothing to from Hong Kong when going back to Pun Ye and Nam Hoi at Chinese New Year back in the early '90's retired with nice German-made, local "NFW" thanks! Benz's off multilingual multi-colour web-offset brochure printing, plastic water-bottle factories and such.

    It's their/our KIDs as are today's go-getters!

    Enterprising folks. Work hard. Work smart. Leave politics - "talking about nonsense" as it translates - to the slow of wit and slothful of foot.

    While OUR fools are jawing with THEIR fools over the politics, the "real power" have "found a ladder", hopped-over the great firewall, gone around the barriers and.... bought another condo, company, county.. or country.

    寄件者

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    Just ran through some quick testing with scope on the field. Everything looks great so far. Little abrupt on the rising edge, will probably throw a bit more resistance on the gate drive to soften it. Plenty of thermal overhead in the design to allow for some inefficiency in the switching.
    pic_9_13.jpg
    pic_9_7.jpg
    pic_9_8.jpg

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