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IndustryArena Forum > CNC Electronics > Servo Motors / Drives > EG&G TORQUE SYSTEMS PMDC servo & MOTRONICS PMDC motor Specs ???
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  1. #1
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    Question EG&G TORQUE SYSTEMS PMDC servo & MOTRONICS PMDC motor Specs ???

    Hi to everyone,

    I've just bought two used PM DC motors for cheap,

    The first one is a "PM FIELD SERVO MOTOR" from "EG&G TORQUE SYSTEMS" Model NO: MH-2120-003J code: 0283. It also has a sticker with three codes like this: ASM:
    E.C:
    E.I.R:
    the codes were hand written.

    The second motor is a "MOTRONICS Corporation" PT.NO. 801679-001 REV.G CAT.NO. 31107-14-210-05 INS. CL. H VOLT 24 DATE CODE 0183. It's a PM DC motor.

    If you guys can help me with these:

    1) On motor #1(EG&G servo) I have no idea of the voltage, Amp & torque ratings...it's a pretty fast motor, supplied it from 6V to 12V to 24V It's fast at 12V & Very fast at 24V (the bearings are old & whistle a bit)

    2) On motor #2 (Motornics) I have no idea of the Amp & torque ratings.

    Any info is welcome .

    Thanks !
    cnc2.
    http://img405.imageshack.us/img405/2378/cimg4042y.jpg
    http://img444.imageshack.us/img444/6...mg4043r.th.jpg
    http://img137.imageshack.us/img137/5914/cimg4044.jpg
    http://img137.imageshack.us/img137/2098/cimg4045.jpg
    http://img152.imageshack.us/img152/549/cimg4046.jpg
    http://img152.imageshack.us/img152/3741/cimg4047q.jpg
    PS: I had troubles uploading the pics to the Zone, I had too many timeouts even when the file sizes were well below the limit, so, I used ImageShack.

  2. #2
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    These EG&G were made by Cleveland Motor Control http://clevelandmotioncontrol.com/index.asp
    If you go to the DC motor link on the site you should see 2120 series.
    If not I have the original manuals.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  3. #3
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    Quote Originally Posted by Al_The_Man View Post
    These EG&G were made by Cleveland Motor Control http://clevelandmotioncontrol.com/index.asp
    If you go to the DC motor link on the site you should see 2120 series.
    If not I have the original manuals.
    Al.
    Many thanks Al

    From the website you pointed I've found this http://clevelandmotioncontrol.com/do...atform2100.pdf & this http://clevelandmotioncontrol.com/do...duct_Guide.pdf and also found an xls sheet http://clevelandmotioncontrol.com/do..._data/2120.xls
    On the sheet I've selected "motor winding type: H" because of the MH-2120-xxxx in the model NO. is that correct ? (the sheet said 1600rpm @45V for winding H but @24V it seemed to be spinning faster than that)

    I'm a bit conserned about the second motor, the fact that you don't know it might indicate that it ain't no good

    Can I change the servo's bearings by myself without the risk of demagnetizing it ? (& loose torque like a stepper)

    Thanks !
    cnc2.

  4. #4
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    I have serviced quite a few without inserting a 'Keeper' but if you want to play it safe, slide a metal tube in place of the armature.
    Careful not to damage or chip the magnets.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  5. #5
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    Thanks for the info, I'll see if I can, I'd prefer to work it out safely.
    cnc2.

  6. #6
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    UP !

    I still have no info about the Motronics Corp pmdc motor & have no idea about the bearing it has on the mounting plate, no obvious indication about its previous life....all I know is that it's made in Little Falls NEW YORK 13365

    Thanks !
    cnc2.

  7. #7
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    I would say the bearing on the mounting plate was due to the particular application it was used in. You should be able to just remove it?
    For sizing, you can get approximately by comparing physical size with CMC motor.
    For voltage, apply a known fixed low voltage DC and measure the rpm, if you estimate a max rpm for the motor to be 2500rpm as a safe guess, then pro rate the max voltage accordingly.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  8. #8
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    Thanks for the reply Al !

    I already know its rated voltage it's 24VDC (on the name plate) RPM is lower than the other motor & I think I'll be able to measure it with my bicycle's multifunction digital tachometer, but I have no idea about its rated current & torque. (by looking inside after removing a plastic plug from the frame I can see the winding which seems to be made out of thick wire near the gauge of phone copper wire)

    Any idea on how I can know the rated current & torque ? (holding the shaft with a towel I could slow it down but I couldn't stop it of course the reading on the amp meter went up to around 3A if I recall)

    Feeding it with 12V & low current I could stop the shaft, but when blocked the motor makes noise sounds like "ggrrrr grrrr grrrr"

    Is there a way to replace a broken brush holder ? it's the outside plastic thread which is broken on the EG&G servo.

    Thanks !
    cnc2.

  9. #9
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    Well, I did the test with the bike's speedometer which has an RPM function in it & it all went out OK.

    It wasn't very accurate but gave a good rough figure because I was holding the sensor in my hand trying to hold the required distance from the magnet (3mm +-1mm).

    The test results:

    the big Motronics has a speed of around 1800 RPM (dancing between 1772 & 1800)

    the moderate EG&G which looked/sounded very fast, has a speed of around 3600 RPM (the speedometer is rated 3600 RPM max & I saw speeds of 3720 RPM)

    All the tests were made with the motors standing vertically on the table.

    Thanks for all the help !
    cnc2.

  10. #10
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    Motronics DC Motor

    "MOTRONICS Corporation" PT.NO. 801679-001 REV.G CAT.NO. 31107-14-210-05 INS. CL. H VOLT 24 DATE CODE 0183. It's a PM DC motor.

    I used to work in the engineering department of Motronics and may have a catalog burried in my files. I will take a look and get back to you.

  11. #11
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    if SBE, ex Motronics, doesn't find an old data sheet on it, post physical size and voltage/speed you got no load again in 1 single post. from that, various of us will be able to compare it to similar rated motors we design, build, sell, service, and be able to make close guess what its current, continuous torque, and max speed ratings are for you.

  12. #12
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    Quote Originally Posted by sbe7922 View Post
    "MOTRONICS Corporation" PT.NO. 801679-001 REV.G CAT.NO. 31107-14-210-05 INS. CL. H VOLT 24 DATE CODE 0183. It's a PM DC motor.

    I used to work in the engineering department of Motronics and may have a catalog burried in my files. I will take a look and get back to you.
    Hi sbe7922,

    Hat's off to the engineers ! this motor is older than me & seems to be in perfect condition, can you tell me on what kind of machinery it was used (for what kind of machinery it was made) ? & what's the purpose of that bearing on the side of the motor's mounting plate ?

    Is it suitable to be used as a servo motor ?

    When I spin the motor's shaft back & forth with my hand, I hear TICTIC as the direction reverts, is it a sign of failing bearings or just the brushes which are a little loose in their cages & move from side to side ? the motor is quiet while running.

    Thanks !
    cnc2.

  13. #13
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    Quote Originally Posted by mike_Kilroy View Post
    if SBE, ex Motronics, doesn't find an old data sheet on it, post physical size and voltage/speed you got no load again in 1 single post. from that, various of us will be able to compare it to similar rated motors we design, build, sell, service, and be able to make close guess what its current, continuous torque, and max speed ratings are for you.
    Hi mike_Kilroy,

    Look at this pic, it's the motor on the right side of the pic:
    http://img137.imageshack.us/img137/5914/cimg4044.jpg

    It's a PMDC NEMA 34 size motor, voltage is 24 VDC but it has no current rating marked on it...its shaft is round & smooth with no key or flat surfaces, the end of the shaft is conical.

    This motor seems to be quite powerful, I did try to stop it by holding the shaft with a thick piece of cloth it barely slowed down with little rise on the amp meter, I don't think it reached 3A, I couldn't stop it & the end of the shaft got hot from the friction with the cloth.

    I couldn't measure the speed under load.

    you'll find more pics in the first post.

    Thanks !
    cnc2.

  14. #14
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    nice heavy duty looking motor.

    the ticking may be result of its previous life maybe running in 1 direction all the time; that would seat the brushes in a way that if you run backwards they will click across the commutator bars. I would not be worried about the sound.

    Answer these questions and I will give you a best guess of what your motor is rated:

    - diameter?
    - full length?
    - rpm at some voltage?

    OK, ur tach checker thing cannot measure speed. do it a different way then. is 24v on it too fast to count rotations of shaft in a given time like 10 seconds? then use jumper cables and put it on your car battery at 12v - can you count revs in given time now? still to fast? put a 1.5v D cell across it surely you can count revs in a given time now!!?? the longer the time the more accurate the result so see if u can count revs for 60 seconds. if possible give us the revs/time for multiple voltages if you want morre accurate motor specs; say 1 d cell, 2 d cells (3v), maybe a 5v power supply, etc. With multiple readings we can solve V=IR+Kb*N and get u better ratings!

  15. #15
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    Quote Originally Posted by mike_Kilroy View Post
    nice heavy duty looking motor.

    the ticking may be result of its previous life maybe running in 1 direction all the time; that would seat the brushes in a way that if you run backwards they will click across the commutator bars. I would not be worried about the sound.
    Will it disappear if I replace the brushes ?

    Quote Originally Posted by mike_Kilroy View Post
    Answer these questions and I will give you a best guess of what your motor is rated:

    - diameter?
    - full length?
    - rpm at some voltage?

    OK, ur tach checker thing cannot measure speed. do it a different way then. is 24v on it too fast to count rotations of shaft in a given time like 10 seconds? then use jumper cables and put it on your car battery at 12v - can you count revs in given time now? still to fast? put a 1.5v D cell across it surely you can count revs in a given time now!!?? the longer the time the more accurate the result so see if u can count revs for 60 seconds. if possible give us the revs/time for multiple voltages if you want morre accurate motor specs; say 1 d cell, 2 d cells (3v), maybe a 5v power supply, etc. With multiple readings we can solve V=IR+Kb*N and get u better ratings!

    Well, motor's diameter is ~78mm length is ~124mm from plate to plate (these measurements were took using a plastic ruler but it should be accurate enough)

    The mounting plate size is NEMA 34.

    Why do you say that my "tach checker thing cannot measure speed" ? I used the RPM function which measures the wheel's RPM by counting every pass of the magnet by the sensor.

    A quick test at 2.5V using a 1000mA power adapter, revealed that the motor is very slow and ticks & turns at a non constant speed, and voltage drops down to ~1V ~1.3V

    At 3V the motor spins at a constant speed without ticking & the voltage drops down to ~2.5V ~2.6V sorry, i could not count the RPM accurately, it looks like it is between 1 & 2 rev per second....the bike's tachometer shows ~166 ~177 RPM ~3.1V becomes fluctuating between 3V & 3.1V

    Edit: when I find more time I'll try to do some testing with my battery charger which has 6V, 12V & 24V at 10A & 5A

    Thanks !
    cnc2.

  16. #16
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    Here is an older link that may help determine torque etc.
    http://www.cnczone.com/forums/diy-cn...o_experts.html
    One way of determining the torque on the shaft in B is with a pulley and a spring scale tied to a cord around the pulley, the torque can be determined from the known dia. of the pulley.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  17. #17
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    if it is brush wear in 1 dir issue then yes, replacing them will stop the noise. it also could be worn down brushes but that should make the noise i both dir. also just running it for a while in the noisy direction should reset the brushes - no need to replace if not worn out. prob best to take then out and look to be sure they are not worn out.

    OK for rating.... let me convert to english: 4.9" long, 3" dia. The torque rating of a motor goes up by the SQUARE of the diameter so this is pretty important to get right. The torque rating of the motor goes up only linearly with the length so that can be less accurate

    Size comparison will get us close to TORQUE rating (nothing to do with speed or amps).


    I am comparing it to a Kollmorgen TT-2031 brush motor of similar size )3"dia x about 5" long: .5/.6nm (4-6#-in) rating continuous.

    MCG model ID3301 is 3.25"dia x 4.78" long rated .5nm (4.7#-in) cont.... similar....

    So I'd say your motor is rated about .5nm or 5#in continuous.

    Now for top speed. At 2.5v you got unsmooth motion, so most of the voltage went toward making torque instead of speed to overcome friction. V=IR+Kb*N. so we want it to rotate fast enough that the IR (torque producing portion) is small compared to the speed producing portion. So we will ignore the 2.5v run for now. somewhere around 3v you got somewhere around 120-160rpm; lets say 150. so the motor constant Kb is 3v/(.150krpm) or 20v/1000rpm. So being rated 24vdc on the nameplate, I would venture this motor is rated about 1500rpm top speed. If you do run it at the higher voltage with the bike tach, this can be made a bit more accurate.... but not sure if tht is so important to you...

    motor Kt rating is same as Kb just in different units, so we can now find the motor current rating from Kb and cont torque rating. Take on faith that Kt=Kb* .085 in our units. so your motor Kt is 1.7#-in/amp. Since it seems rated around 5#-in torque, its current rating is 5*1.7=8.5amps.

    So you have an 8.5amp cont, 5#-in, 1500rpm max speed, 24vdc brush motor.

    If you want to check some more, you can put a torque wrentch on the shaft (or use pulley and weight like Al's link) and measure the current into the motor as you load it upto 5#-in torque; you should get around 8.5amps. If you leave this on it and watch the motor temp, it should not get too hot to keep your hand on it for about 3 seconds; if it does, our torque and amp rating is a tad too high. If it does not get this hot then our torque and amp ratings are a tad too low. But for cards I think if you used a 8amp cont/16amp peak 24vdc output drive like a small AMC you would run this motor very well.

  18. #18
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    Thanks for the replies guys !

    Thanks for the link Al, I don't have a spring scale yet, but i have a torque wrench & will try to use it to measure the motor's torque, it'll be a bit tricky to find a way to couple the wrench to the shaft.

    Mike, your approximation is interesting, but I'll try to do more accurate testing later, just to be sure/confident. I always thought I could stall 0.5 Nm by hand ....One thing bothers me a bit in your aproximation: a while back I've been told that 1Nm of torque requires a motor of around 100W of power. But when I do the calculation backwards using your numbers I find that the motor has three times more torque than you've found ???

    If we take U*I=P, we end up with 24*8.5= 204W of input power, with an efficiency of 0.82, we have 204*0.82= 167.28W of output power which is equivalent to approx 1.6 Nm of torque. ???

    A while back in a mailing with a Leroy Somer tchnician about an old motor they made, he found in their archive that the motor was rated [email protected], but he couldn't tell me weather it was the continuous or peak rating, I asked him about the heating ...etc & he told me that I have no way of testing it outside of a lab environement because the varnish on the winding might burn before the motor's case gets too & ruine the motor.

    Maybe your testing technique is for testing the temperature to prevent demagnetisation. but what about the wingdings ?

    PS: don't be pissed off, I might be totally wrong, I'm no E engineer & have no experience with electric motors...etc. I've just read a lot of Al's posts & discussed with that Leroy Somer guy about one of their old motors, I was going to aquire from a scrap yard, it was a bit pricey & had no rating on it exept date code & part number because they made it for Honeywell bull.

    Thanks !
    cnc2.

    EDIT: I forgot to mention, I'll be using UHU servo drives on the three axes.

  19. #19
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    where is my reply from yesterday 4pm? cnc2, I sent another long reply but is not here! took me about 20 minutes to compile (:

    bottom line was

    1) I'm by no means p'ed! but happy u r digging in on this! -
    2) I also showed ur rule of thumb is dependent on rpm so using it I got motor rating closer to 1nm
    3) my .5nm was based on looking at similar motor sizes and their cont rating (a rule of thumb is similar size motors have similar continuous torque ratings; torque rating is determined by mass and size. speed, peak torque, amps, volts are all engineered and can be almost anything in a given size motor.
    4) this cont torque rating is that: continuous - what the motor can put out forever w/o overheating, NOT max or peak torque. so if you apply correct volts and current to this motor rated .5 or .75 or 1nm, it will put out a peak torque - probably around 5nm! that is why u cannot stop it by hand!
    5) DO run the motor on 12v car battery and get your bike tach reading; I calced based on numbers down in the mud at 3v... do 12v and we will have a good speed to work with! remember, this test will let us calculate current rating and max speed rating of the motor, not cont torque rating; that is determined by physical size only. two different 'tests' to get your full motor data.

    there; this summary reply took only 5 minutes! If you want to see the 1nm 100 rule thing I can post calcs showing that later.

  20. #20
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    Hi Mike, thanks for taking the time !

    In my mailbox I saw that you replied on this thread without reading the email, I opened the link to the thread, checked out my other emails then, got out of my mailbox to take a look at this thread...but I didn't find your post, I could swear I saw your post in the email, but I had no time left to recheck...So, here's your previous post:

    Quote Originally Posted by mike_Kilroy
    Here is the message that has just been posted:
    ***************
    cnc2,

    Thanks for double checking my! I appreciate it when someone will check me - much better to get the right answer if I mess up than give the wrong one, so nope, I am happy, not p'ed! Your 1.5 & 3v were down in the mud and may be giving misleading info.

    Let's check your rule of thumb idea another way too, but with the real values.... 1nm is a torque, and it needs a speed associated with it to get a power so lets use the 1500rpm I think your motor will go. so HP=T*N/7121 where T is nm, N is rpm. so 1nm*1500rpm/7121= .33HP... .21hp*746w/hp=157watts.... I like your eff of .82, prob close at speed, so 157/.82 means you need to put in 191watts for 1nm working it backwards... so .5nm would calculate this way to half that - 96 watts.....hmmmm looks like I may be off by a factor of 2 like you say! Only problem is if the Kb is off, so is the Kt and so if they go up so it turns out rated 1nm, the max speed will come down by 1/2 too to 750rpm or so and so the hp & watts will be the same again! Only way to get the power down to match the Kb/Kt numbers would be to have it rated 1/2 the current... something is not jiving. Guess you will have to run it at higher voltages to get it up out of the mud so we can get better numbers. All we need is a good speed reading at a decent voltage (12?) to clean this current rating part up.

    The torque rating of 1/2nm was based on similar physical size motors. Since torque goes up by the sq of the dia and up l linearly by length of the actual motor portion (dont count the bearings and brush length), it was easy to see this size motor should be around .5nm comparing it to other similar size brush motors. There is no magic here. I assumed this motor had better than ceramic magnets, so I already assumed it would have higher output torque than a low cost same size motor.

    Keep in mind also when considering stopping the shaft that this is the THERMAL OR CONTINUOUS torque rating; as you know motors will output easily 5-10x more torque intermittently if they get enough current, so when you try to stop it by hand, you will be getting much more torque depending on your power supply capability. so you really need an ampmeter in series with the motor lead to verify the current pulled as you load it by hand for the feel tetst - which is probably accurate too!

    So get that bike tach hooked up and run that puppy with 12v and let's see what that calculates out to!
    ***************
    Well, I have no car battery, so I'm using the battery charger:

    Test 1
    When measuring no load voltage on the charger set to 6V: it reads 6.99V 7.0V
    When measuring voltage when the motor is running from the charger set to 6V: it reads around 8.4V (it increased) and bike tach's RPM reads 540rpm/531rpm.

    Test 2
    No load voltage is 12.35V when the charger is set to 12V.
    When measuring voltage when the motor is running from the charger set to 12V: it reads around 16.5V (it increased too) and bike tach's RPM reads 1031rpm

    At 24V the tach reads 1800rpm.

    At 6V no load the motor draws up 0.22A 0.23A in one direction and 0.24A 0.25A in the other direction but the rpm reading is the same in both directions.

    At 24V no load it draws up around 0.8A but after trying to stop it by hand it draws 0.22A at no load.

    At 24V I try to stop it, but I only slow it down from 1800rpm to around 1100rpm & it draws up to 1.7A-------In the other direction I had a better hold on it & could slow it down to 840rpm & the ammeter read around 2.4A (I'm not sure it wasn't a peak, because i looked at the meter & released the shaft just before my fingers start burning) Well could slow it down to 945rpm & it read 2.6A then at 814 it read around 2.7A.....I'll have to find some rubber band which will have more grip than a piece of cloth without risking to burn my fingers

    Edit: after testing with a piece of rubber, I could slow it down to 900rpm and it read around 2.45A, the rubber melted a bit(but not my fingers) but it was a relatively accurate read. After all this testing, the motor case is a tiny bit warm. when the charger is set to 24V the volt meter measures 20.3V with no load. there's something weird with my voltmeter, when I try to measure the voltage when the motor is running unloaded, the reading goes completely wrong, it doesn't care about polarity anymore & it reads 24V 35V 50 58 78V...crazy sh*t.

    Just to make sure: my ammeter is wired in series after the motor( V+ >>motor+; motor- >>ammeter+ ; ammeter- >> charger-) is it the correct way to use it ? (I think the poles are OK because when I invert the ammeter's poles it shows me a minus sign) so, is it correct to put the ammeter after the motor ? (I use it very rarely)

    This bike tach is not accurate at all ! its original magnet is still on the bike's front wheel & i'm using a little magnet I scraped from a CD drive lens mechanism, when the magnet has its wide area facing the sensor it reads something & when it has its side (half the previous area) facing the sensor it reads twice the previous number

    That's it for today, I think you have enough numbers to play with

    Thanks !
    cnc2.

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