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VFD tuning for a Marathon motor

Discussion in 'ELECTRICAL ISSUES - POWER YOUR MACHINES & SHOP' started by cut2cut, Apr 9, 2017.

  1. cut2cut

    cut2cut United States Active Member Active Member

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    I need some advice tuning my VFD to my inverter motor. I've been running it at 60HZ but wish to run the VFD at 120HZ for double the rpm.

    I have a Delta VFD-E ( 230V ) and a Marathon Inverter motor ( this is a different motor than what came with the mill ). Its working "ok" with the original default settings ( that were for the original motor ) at 60HZ but I just replaced the spindle bearings in my mill so they can now handle 7000 rpm ( with my 2-1 ratio pulley ). At 60HZ my motor turns at 1750 rpm and with the gear ratio I'm achieving 3500 rpm at the spindle. I want to run the motor at 120HZ so I can get 7000 rpm maximum *spindle rpm ( which is 3500 rpm on the motor )

    The VFD manual suggests I need to alter the mid point Frequency ( section 4-48 / parameter 01.01 ) . I'm not sure what to set it to. Also, when I attempted to set ( section 4-49 / parameter 01.05 ) to 2HZ the VFD error-ed and it auto set it back to the default 1.5HZ. The range is supposedly .1 HZ to 600HZ, so it must have some override if other settings aren't correct. I'm just not confident I can figure this puzzle out myself and hopeful someone experienced can lend a hand.

    enclosed are pictures of the Motor's specifications and also the VFD manual settable parameters for tuning the motor.

    And a link to the VFD manual is here :

    http://www.delta.com.tw/product/em/.../manual/Delta_IA-MDS_VFD-E_UM_EN_20140912.pdf

    Jake

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    Last edited: Apr 9, 2017
  2. Maddogmech1

    Maddogmech1 United States Active User Active Member

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    Maybe your drive is more complicated than the ones I use, but on mine I simply have to set the max output frequency to whatever I want, in your case 120hz.


    Sent from my iPhone using Tapatalk
     
  3. mksj

    mksj Active User H-M Supporter-Premium

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    Please see the attached basic parameter changes. The upper frequency is set by parameter 01.00. The Fbase is the base frequency of the motor or 60Hz, the mid-point I would leave at the factory default, this is not the half way point in the frequency range. Often two parameters will be tied together, so something like the minimum output 01.05 needs to match the motor minimum output 01.28. The motor type and load need to be entered into the MOTOR 1 parameters, the default poles is 4 for a 1750 RPM motor. The default PWM frequency 02.03 is 8kHz, if you have a lot of motor whine this can be set to 12kHz. There are a number of other parameters that may need adjustment depending on the control inputs and to do some tweaking.
    Delta VFD motor parameters .jpg
     
    Last edited: Apr 9, 2017
  4. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    The motor plate shows it will go to 5400 rpm safely, so you could run it to 180 HZ to achieve that. Whether that is a good idea or not depends on other factors, including the spindle bearings. You did not mention what kind of mill it is. Sometimes there are other parts of the machine that will also limit the speed, like perhaps a variable speed drive. Make sure everything can handle the additional speed.
     
  5. JimDawson

    JimDawson Global Moderator Staff Member Director

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    That is a nice motor/drive combination.

    In addition to what @mkjs said above, I would set up the drive for Vector Control 00.10 = 1. much better torque control, and overrides some of the setup parameters.
     
  6. cut2cut

    cut2cut United States Active Member Active Member

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    wow. Thank you @ mksj. I'll try those settings

    I have noticed the motor whine a bit, so I'll try adjust the PWM frequency too. I race RC cars, so I'm familiar with tweaking PWM but the speed controls for RC are far more "user friendly" / simple so outside of timing manipulation these VFD's are more complex beasts. btw, I falsely thought that Motor 1 settings might be just a series of presets. ( Motor 0, Motor 1, Motor 2 ).

    I received an over voltage fault while lowering the rpm, so I am told I need to increase the deceleration time parameter.

    @ Jim, does Vector control require feedback from the motors encoders ? Or is this just a setting. Its becoming more and more apparent that I should look in the manual a little deeper ( understatement of the year ! ). I actually have a durapulse VFD that I plan to use, which has a feedback encoder card.

    @Bob, I just got done installing Angular Contact Bearings in the spindle that should be good for 7k rpm. At this point, due to the gear ratio, I think if I used a higher frequency I'd lose too much torque and don't really need more rpm. If I need that sort of rpm, I'll probably get a 20k rpm high speed spindle to attach to the side of the head of my mill. In fact, that is something I thought to do someday.

    Jake
     
  7. JimDawson

    JimDawson Global Moderator Staff Member Director

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    It depends on if it is a sensorless vector drive. I may have been making a bad assumption on that count, the Delta may or may not require an encoder. I didn't try to wade through the entire manual.

    The DuraPulse is a sensorless vector drive with an easy to use autotune feature. I have one on my mill and am very happy with it. Speed control and constant torque are great, especially at low RPMs.
     
  8. cut2cut

    cut2cut United States Active Member Active Member

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    The only reason I haven't installed the Durapulse drive yet is because it physically is a bit larger requiring some "adjustment" to my electronics cabinet. hmmm, ok, I'll look into it now as you are making it look like I should just jump in and get that done sooner than later! :)

    Cheers,

    Jake
     
  9. JimDawson

    JimDawson Global Moderator Staff Member Director

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    The one thing on the Durapulse is the braking resistor function, in order to turn it on, it is cryptically labeled '' overload protection'' in the manual. Required a call to tech support to figure that one out. ;)
     
    cut2cut likes this.
  10. cut2cut

    cut2cut United States Active Member Active Member

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    I do have the braking resistor, so this is certainly good to be aware of ! Thank you
     
  11. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    My concern was not about the spindle bearings or the motor, which I assume your researched to be adequate for the speeds you intend. Beyond that, there may be other components of the drive system that are not up to the speed increase. For instance, a Bridgeport variable speed pulley system. Or something else... We don't know what mill you have...
     
  12. cut2cut

    cut2cut United States Active Member Active Member

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    Sorry Bob, after you asked I put my mill info in my signature and forgot to mention it. It's a Precision Mathews 1100+ pound "bench top" 3 axis metal CNC
    Mill. Model# : PM -940 CNC . I've removed the gearbox and replaced it with a pulley and belt at at 2:1 ratio.

    Jake
     
  13. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Sorry I missed your signature change. It sounds like you are only changing speeds with the VFD and now have no additional drive parts besides the two pulleys, the motor, and the spindle. If so, you should be fine, at least at the high speed end. At really low speeds you may not have enough torque and cooling for heavy work, or have you considered that?
     
  14. cut2cut

    cut2cut United States Active Member Active Member

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    Yes, at least initially I intend to adjust the VFD frequency when I need more torque, and down the road I intend to create a two pulley gear reduction setup for the ultra low rpm stuff. Right now I am basically just getting the mill functional and optimize it as I go. I do think about the possibility that I'll lack enough torque but have yet to mill enough to know if it's ok for my needs. It's been an "experience" just getting linuxcnc working and getting accustomed to the interface and new hardware. Baby steps :)

    Cheers,

    Jake
     
  15. cut2cut

    cut2cut United States Active Member Active Member

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    I just tried those settings. It worked a charm ! I can't say for sure, but I think torque may have increased, while also doubling the rpm ! Can't thank you enough.

    ( I put some drag on the spindle at 500 rpm and it didn't seem to slow much at all. I won't tell you how I did it, as my mother would not approve :) ).
    It may have to do with some of the settings getting bumped from 50 to 60hz that you pointed out.

    I also changed the PWM from 8k to 12k. This proved to reduce the motor noise. Getting closer to my goal of a silent mill ... lol :) I believe sometimes increasing the PWM can increase motor efficiency and possibly even torque ( although I previously equated lower PWM frequency with an increase in torque. A friend explained it has to do with matching the correct PWM with the inductance / windings.

    I think I'll use this Delta VFD for a while before switching to the other VFD. Its working and its always nice to be able to compare stuff.

    Cheers,

    Jake
     
  16. Jim Nunn

    Jim Nunn United States Steel Registered Member

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    The limiting factors on the maximum speed assuming the rotor is balanced and the bearings are capable of higher speeds. Is the internal fan in the motor are how much torque you need at these higher speeds and the surface speed limits of the belt pulleys/ gears.

    the motor is a constant torque device up to its rated base speed (4pole /1800rpm) and a constant HP machine past its rated base speed. What this saying is that from minimum RPM to 1800 RPM a 1.5 Hp motor produces 54 inch pounds torque but at 2600 RPM it produces 27 inLbs Torque and at 5400 RPM 18 InLbs. The second issue is that the HP required to turn the internal fan is 8 times higher at 3600 RPM and 27 times higher at 5400 RPM. Somewhere between 3600 and 5400 the motor may stall out simply because the HP required the spin the fan has exceed the motors capability. This is based on the affinity laws which states that the work (HP) required to turn a fan increases by the cube of the speed change.

    As for the Pulleys/gears they have Feet Per Minute (FPM) rating that if exceeded they will fly apart.

    The main difference between the various drive architectures (Volts/Hz, Sensor less Vector, Flux Vector) is how well they can produce torque at very low speeds, and how well they hold speed accuracy. Also with Flux Vector you will the ability to control Torque.

    So set the drive up as if your max speed is 1800 RPM/60Hz. If the drive has an auto-tuning feature auto tune the drive. This is usually found in the SVC and FV drives. Then set the max Hz to say 120 Hz and use the machine. if it appears you have enough torque then up the speed until the machine just starts to slow down and you will be at the drive/motor maximum capability.

    The Delta drive is a very good drive. several of what you would think of as the major drive manufacturers are rebranding the Delta drive. The Marathon MAX Plus motor is a top notch motor and is only exceeded by the Black Max and the Blue Max motors . you have some good stuff there.

    For what it's worth I have designed, applied and sold drives for over 45 years and I do not have an inverter on my lathe I prefer using the belt pulleys because they are torque multipliers and what you need to hog out metal is torque, high speed is for polishing.
     
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