10ee MG RPM slows from 800 to 500 under load
Close
Login to Your Account
Page 1 of 4 123 ... LastLast
Results 1 to 20 of 61
  1. #1
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default 10ee MG RPM slows from 800 to 500 under load

    Recently reducing the size of a chuck adapter back plate on the 10ee. Plate was about 10" in diameter. I was reducing the diameter to fit a chuck. The lathe was slowing from around 800 rpm to 500rpm when I was making the cut. IS this a brush timing issue? What do you think? thanks. Rich

  2. #2
    Join Date
    Feb 2002
    Location
    Peralta, NM USA
    Posts
    5,987
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    615

    Default

    As a first step I'd hang a voltmeter across GA1 and GA2, then GF1 and GF2 and see what changes when you see the slowing. I would expect that you'll see something on the armature voltage and that you need to look at the brushes and commutator on the generator end of the drive.

  3. #3
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default

    Quote Originally Posted by rke[pler View Post
    As a first step I'd hang a voltmeter across GA1 and GA2, then GF1 and GF2 and see what changes when you see the slowing. I would expect that you'll see something on the armature voltage and that you need to look at the brushes and commutator on the generator end of the drive.
    I opened the motor peckerhead and put a meter on the armature and the field terminals. Armature voltage drops about 10 volts when the motor is under load. field stays the same
    What's next?

  4. #4
    Join Date
    Feb 2002
    Location
    Peralta, NM USA
    Posts
    5,987
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    615

    Default

    Looking at the spindle motor how do the brushes and armature look? Are the gaps on the armature clear and clean? Brushes have proper tension, length? Nothing loose? What does it look like running - is there significant sparking from the brushes in forward? Reverse?

  5. #5
    Join Date
    Jul 2007
    Location
    Missoula Mt
    Posts
    1,398
    Post Thanks / Like
    Likes (Given)
    62
    Likes (Received)
    675

    Default

    Have you done any rewiring? Could s1 and s2 be rev?...Phil

  6. #6
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default

    i will check the brushes and commutator on monday
    previous owner might have rewired some wires
    where is s1 and s2?

  7. #7
    Join Date
    Feb 2002
    Location
    Peralta, NM USA
    Posts
    5,987
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    615

    Default

    I think the compound winding is on the generator end of things and not the spindle motor end of things. At least all of the blueprints I can find incate that (3216 & 3218). If that's the case with his *and* the armature voltage isn't changing (much) then I suspect the series field is correct. So checking at GS1 and GS2 on the terminal string in the middle of the base you can find both. If the previous owner has been in there you might need to trace the lines from there to the generator peckerhead and also to the DC panel with all the relays. GS1 should trace from the generator through the terminal strip to the DC panel to A1 when in forward, A2 in reverse.

    In case someone reading this doesn't know what a compound wound motor is for:

    10EE Ward-Leonard System Detailed

    All in all: I don't know if 10v is *that* much on load. Anyone else know?

  8. #8
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default

    I installed a dc power supply as a replacement for a non working exciter. Could the polarity be reversed?

  9. #9
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default

    I switched the polarity of the power supply- no change
    checked commutator and brushes on both the generator and spindle motor. brushes look like they have been changed within a few years. springs look good, commutators reasonably clean.
    not much sparking in either direction

    so here is how it is operating
    facing mild steel 3" diameter- cut .052"
    rpm 800 no load speed, rpm drops to 700 under load.
    armature voltage starts at 252v no load, drops to 244v under load
    field voltage stays the same
    Maybe it is within normal range. IDK
    Thanks for your help

  10. #10
    Join Date
    Feb 2002
    Location
    Peralta, NM USA
    Posts
    5,987
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    615

    Default

    As Phil suggested it might be something with the generator series field. It's there to prevent this sort of thing. A quick check would be to reverse the generator motor connections for S1 and S2 at the terminal strip and see what happens with a load. If it *really* slows then they were right.

  11. #11
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default

    ok I switched s1 and s2 on the terminal strip.
    here are the results
    cutting aluminum 7-1/2" diameter .080cut off the diameter rpm dropped from 800 to 700 voltage across armature dropped 20v

    after switching back to original configuration
    same .080 cut off diameter rpm dropped from 800 to 725 armature voltage dropped only 8v

    so with the orig configuration the rpms dropped less and the voltage drop across the armature was less than half

    I think i should leave it in the original configuration and call it good
    what are your thoughts?

  12. #12
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    20,205
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    12010

    Default

    Quote Originally Posted by lectrician1 View Post
    I installed a dc power supply as a replacement for a non working exciter. Could the polarity be reversed?
    The DC power supply has no ARMATURE load-sensing compensation circuit. It is designed to hold a specific Voltage as its OWN load varies. ONLY.

    The OEM Exciter DID have load sensing. It was tuned to work dynamically with the generator- all as a well-balanced "team", so to speak.

    As load increased, Exciter and generator drew greater field current through the primary generator so the Armature Voltage actually went UP to deal with the load. Your rig isn't delivering increased Field power. Holding it STEADY, rather.

    That "dynamic" response was a MAJOR part of the exciter's job.

    But it cannot do that job if it is no longer THERE and its replacement has a different prime directive.

    A Parker-SSD DC Drive has its OWN IR sensing feedback loop. Built-in.

    Or can be switched to read from a tacho-generator, instead, for around 20 times the precision, given it also expands the covered RPM range. Check the comparison table in the manual.

    Either way, it also boosts Armature Voltage to hold RPM under load. Doesn't need a Field involved to "JFDI". "Op Amps" and reference source sensing current flow, ELSE tacho-generator feedback as input, rather.

    "RTFM".

    Even if you do not have one of the drives.

    It's a free download. And very educational. Same again Eurotherm-SSD's manual on their Field Regulator system in a separate box.

    Load regulation was what the brilliant (in MANY things) Harry Ward-Leonard brought to the party. He was otherwise not the first to ever build a Motor-Generator rig. Just the first to build an elegantly simple, stable, repeatable under load, and eminently controllable VERY GOOD one. Serious DURABLE, too!

    One of over 100 patents. If it matters. As it should do:

    Harry Ward Leonard - Wikipedia

    Simply put? Your rig has none of the above.

    Can't "get there from here" if it is indifferent AKA blind to the inherently self-regulating feedback all others put to good use.

    TANSTAAFL .. all part of the "invisible" AKA "black magic" goodness of a(ny) OEM DC Drive 10EE, any era.

    Absent that "stealth", built-in and taken-for-granted, feature, a drop in RPM under load is "just going to happen".

    JFDWT.. or seek out a salvageable "rotating" exciter.. or even an SSD drive.
    Depending on how much it actually matters to yah?

    It might not be a big deal, given "ordinary" lathes often drop RPM a skosh under load, anyway? And still make PLENTY of useful chips.

    Just not as "elegantly".....


  13. #13
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default

    its not that big a deal. so i will keep it as is. machine is going to a new owner anyway.

  14. #14
    Join Date
    Sep 2002
    Country
    UNITED STATES
    State/Province
    Arizona
    Posts
    4,049
    Post Thanks / Like
    Likes (Given)
    1029
    Likes (Received)
    643

    Default

    WillRay had a similar sounding problem with his square-dial MG machine. The previous owner had tried to rewire the machine and gotten a lot of things wrong, on top of that, the motor shop that rebuilt the motor/generator had improperly connected the series field and inter-pole windings. Here's a link to the thread, the stuff about the generator windings starts at about page 4: Un-hacking 10EE Motor-Generator wiring

    Cal

  15. #15
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default

    there are new wires coming out of the generator and other places around the dc panel. not all wires were replaced though. Not sure how I should proceed. I think the lathe works fine except for a slight slow down while cutting some hard steel at about 9" diameter. I think it is acceptable.

  16. #16
    Join Date
    Mar 2012
    Location
    Las Vegas
    Posts
    838
    Post Thanks / Like
    Likes (Given)
    14
    Likes (Received)
    105

    Default

    Thanks CAL!
    I sent Willray a PM. I hope he is still active on the sight.

    Quote Originally Posted by Cal Haines View Post
    WillRay had a similar sounding problem with his square-dial MG machine. The previous owner had tried to rewire the machine and gotten a lot of things wrong, on top of that, the motor shop that rebuilt the motor/generator had improperly connected the series field and inter-pole windings. Here's a link to the thread, the stuff about the generator windings starts at about page 4: Un-hacking 10EE Motor-Generator wiring

    Cal

  17. #17
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    20,205
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    12010

    Default

    Quote Originally Posted by lectrician1 View Post
    its not that big a deal. so i will keep it as is. machine is going to a new owner anyway.
    It isn't rocket science to build an analog Field power supply that COULD sense the load's need and boost the output so the primary generator's stronger field COULD perform the same Armature boost function as the exciter/MG combo.

    ISTR Reliance themselves (and perhaps "not only"?) DID that in an early "exciter- less" MG drive that retained the smooth "rotating power" of the generator rather than choppy Thyristors, but used "active" solid-state Field power - EG: - with load regulation included?

    Such a combo would cost more than present-day solid-state drives, if a new DC generator had to be supplied, too... but be very hard to beat for smooth power at the spindle.

    If repair schematics could be found, that rig could be duplicated without need of re-engineering .. .cheaply, too.. it doesn't handle anywhere NEAR as much current nor even as high a Voltage as the Armature side does ...and the "lab appliance" DC bench supply put back to general-purpose use.

    2CW

  18. #18
    Join Date
    Feb 2002
    Location
    Peralta, NM USA
    Posts
    5,987
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    615

    Default

    There was a series field in the original exciter (at least shown in 3216 and 3218) so it's possible that's the reason for some of the slowdown.

  19. #19
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    20,205
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    12010

    Default

    Quote Originally Posted by lectrician1 View Post
    there are new wires coming out of the generator and other places around the dc panel. not all wires were replaced though. Not sure how I should proceed. I think the lathe works fine except for a slight slow down while cutting some hard steel at about 9" diameter. I think it is acceptable.
    Per our mid-day phone chat, strongly recommend restoring to the OEM exciter.

    Especially since you still have it.

    The threads already cited are a good guide.


  20. #20
    Join Date
    Sep 2002
    Country
    UNITED STATES
    State/Province
    Arizona
    Posts
    4,049
    Post Thanks / Like
    Likes (Given)
    1029
    Likes (Received)
    643

    Default

    Is the E1-E2 voltage dropping under load?

    Cal


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •