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[Noteworthy] VFD & BP Series 1 speed adjustment

Discussion in 'ELECTRICAL ISSUES - POWER YOUR MACHINES & SHOP' started by AxeMaker, Feb 10, 2017.

  1. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Hello,

    Not sure if this goes into this forum or the BP forum but here goes...

    Okay my BP Series 1 has a 3PH motor which was wired for 460v 3PH. I installed a VFD to drop it down to 1PH and I re-wired the motor to 220v. It runs, no problems there...

    I am trying to figure out the best way to word this so if it doesn't make sense I will try again... but here goes.

    If the BP is physically set to 300 RPM do you run into any physical problems in the gearing/belts if the VFD runs the motor at, let's say... 3000RPM even though the BP is set to 300RPM?

    Seems like in some speed change instances you could run into a overspeed problem. Does that make sense or am I not totally understanding the BP operation?

    I am thinking that if the speed is set using the BP speed adjustments there are gears/belts that turn within certain RPM specs and if you introduce an external device to make the motor run faster even though the gearing/belts are set to not go fast you run into some kind of RPM overspeed.

    Am I just overthinking this?
     
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  2. cathead

    cathead Active User Active Member

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    The main thing is not to over speed your motor by setting the VFD frequency maximum too high.
    Stay within the motor speed ratings and you will do just fine. The gearing and or belts will take
    care of themselves. What I did was set my belts (step pulley machine)to run at about 800 rpm
    and that way you can control the spindle speed from slow to fast with the VFD frequency. If I
    ever need more or less speed, I can use a different pulley. I set it up over a year ago and so
    far I have not had the need to change the pulleys. Also, when drilling large holes or using large cutters, the back gear gives me a whole new range of abilities. At 60 Hz, the back gear
    is at 98 RPM so one can go as slow as needed for power tapping or up to about 500 RPM for another
    whole range of speeds...
     
    Last edited: Feb 10, 2017
  3. Bob Korves

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

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    I assume you have a multi step pulley speed change system on your lathe? If you think you can set the belt in one set of grooves on the step pulley, and then control the speed from zero to multiple thousand RPM's, you will be disappointed, and may break something. You can lower the spindle speed with the VFD, and the motor will turn nicely at low speeds, until you put a real load on it, then it will stall. You can increase the power output to the motor with many VFD's but then the motor can also burn out because of insufficient cooling. You can over speed the motor by setting the frequency higher than 60 HZ, which is not recommended for ordinary motors, and can also make them fail. Also, the bearings in the head may be destroyed by running them over speed. You really have to use it as a fine adjust. With ordinary motors, you might run it from, say 40-65 HZ and get some additional speed control without over stressing anything or losing much torque or cooling. Over speeding is not a real good idea, but it is tempting. A machine with a head made to handle the RPM and a vector motor can do it, but all the components are designed for the job. Hope this makes sense, perhaps someone smarter on this than I can chime in.
     
  4. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    No I have a Bridgeport Series 1 Mill that has the speed adjustments on the front of the head. The VFD also has the ability to adjust speed.
     
  5. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I am not sure there is what you would call a normal pulley in the BP. There are gears and a timing belt. I was using the pulley description as an example of overspeed.

    [​IMG]
     
  6. JimDawson

    JimDawson Global Moderator Staff Member Director

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    I had a V/Hz VFD on my variable speed head, I ran it between 30 and 65 Hz. So no danger of over speeding the motor or pulleys. Had a speed range of about 30 to 4500 RPM depending on low or high range. The motor runs at a nominal 1800 RPM at 60Hz, if you are in low range at maximum RPM on the variable speed, the motor is still turning at 1800 rpm, so the spindle pulley is spinning at about 4200 RPM, but the spindle is geared down to about 525 RPM or so. The variable pulleys have a total range of about 7:1

    A normal 1800 RPM motor should be safe at 3600 RPM, but with a variable speed head you don't need to run it that fast. 4200 rpm is fast enough for most work. And I wouldn't want to turn those big VS pulleys much faster than that. :eek:

    If you need a high speed spindle, then your next project will be to hang a router motor off of the quill.:)

    I hope this makes sense.:confused:
     
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  7. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Yes it make perfect sense! May be not this particular thread, but this subject should be made into a sticky or added to an existing document as it relates to VFD/Bridgeport operation. It, for new owner/operators, would be very good information. Especially given the safety implications.
     
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  8. Keith Foor

    Keith Foor Active Member Active Member

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    Short story on a VFD.
    you can NOT expect to park the variable belt drive on a machine in one setting and have full speed range control via the VFD.

    Remember that a mechanical lowering of the spindle RPM via gearing will increase torque tremendously, decreasing RPM via a VFD does NOT increase torque on the spindle so parking a 3 inch shell mill in the spindle, setting the mill drive to 2000 RPM then turning the VFD down to 200 RPM is not going to work. The spindle will stall.
     
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  9. AxeMaker

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    This is a perfect example of why I suggested this be a sticky. I have not seen most of the info people have posted here before.

    Wouldn't it be best to just set the VFD at whatever hz and other parameters the motor is and plainly use it as a power supply, then just use the speed adjustment controls on the mill?
     
    Last edited: Feb 14, 2017
  10. Bob Korves

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    That would be safest for the machine and for the motor (and for the operator), and honors the manufacturer's intentions and instructions. Once you move outside those parameters, your become the test pilot...

    Edit: And on your variable speed machine there is not much real reason to use the VFD for more than simply supplying three phase power.
     
  11. mksj

    mksj Active User H-M Supporter-Premium

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    There are various iterations on how to use a VFD depending on the system and how it is installed. Most smaller factory installed VFD mills and lathes have 2 mechanical speeds and the motor is used over a 10 fold speed range, usually something like 20-200Hz. The motors are usually oversized, so that the Hp which decreases in a linear fashion below the base speed is sufficient at the lower speeds. They also have an electric blower or are TENV. When you over speed a motor beyond its base speed, the Hp stays flat (up to a point) and you are delivering more Hp to the spindle (when factoring in the mechanical ratio change) then with a fixed frequency motor with a mechanical speed adjustment.

    In your situation with a varispeed type of head, your are probably better off using the mechanical adjustment for most of the speed range, also using a fixed mechanical speed would cause uneven wear in one point. What is often done in a mill VFD conversion would be to use a larger (2 or 3Hp) inverter motor and do some form of direct belt drive. With the stock 1 Hp motor you would loose too much Hp using the VFD as your primary adjustment. I also had seen some postings that the Bridgeport pancake motors were a bit more difficult to drive from a VFD stand point, so you may want to go with a 1.5 or 2 Hp VFD, and dial it down to the settings on your motor. The VFD can also provide something on the order of 120-150% overload capacity for up to 1 minute, but this can be a problem for non-inverter motors. There have also been some posting on this site of people using the Lenze or Leeson SMV VFD with good results on this machine. I would set the maximum frequency to something like 75Hz, and use a VFD range of something like 45-75Hz, or use it in a fixed 60 Hz frequency and just use the start/stop and reverse controls.
    http://www.globalindustrial.com/p/m...or-series-drive-vfd-nema-1-3ph-1-5hp-200-240v
    https://www.wolfautomation.com/esv112n02yxb-ac-drive-1-5hp-208-240vac
     
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  12. AxeMaker

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    My VFD is a Lenze 3HP. The motor on my BP is 2HP. I went ahead and bought a VFD that was rated higher than what I had.

    I cannot remember who gave me the info, but I drove over to Automation Direct and picked up the start, e-stop, fwd/rev, buttons or switches and have them mounted into a small box. I am now wondering if that wasn't a waste of money ( at least some of it) because if I just use the VFD for "power" for the most part, I don't think I will need everything I bought.

    With so many to-do's in the garage getting everything setup, moved around, getting power run etc... I just have not had much time to get out there and really dig in and play with it. Which brings me back to the reason for my post... I want to make sure of what I "need to do" given the type of milling machine I have.
     
  13. Keith Foor

    Keith Foor Active Member Active Member

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    It seems to me that a review of the use of VFD's in industry for the intended purpose would tend to shed a lot of light on whats proper and frankly what's not.
    The two uses I have seen are fan controls and material handling IE conveyors.

    Fans are straight forward. But they are only varied to 30 to 50% on the bottom side and are never setup with the idea of going over 100% speed.

    Conveyors and material handling are all configured the same. The VFD runs a gear reduction motor that drives the conveyor or other material handling device like a spin table, auger, or a take up real for cloth.
    Again with this you are gear reduced so torque isn't as much a factor. And the speeds are more a product of the gear reduction than the motors ability to vary RPM a great deal.
    A lot of this stuff is using 90 to 1 or 128 to 1 reduction. So if you look at the math, 3450 divided by 128 is 27 RPM. Then take the motor to 1000 RPM and you get 3.45 RPM. So the speed change is going to be linear, but if you think cutting tool, it's 25 RPM. It don't matter much in milling and turning.

    Thats why it's typically better to use a RPC or run a VFD at a fixed setting and vary the machine through its mechanical means.
     
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  14. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Great explanation ! The only thing I was stumped on is the abbreviation RPC. What is that? (of course as soon as you type it I will say to myself "oh yeah I knew that") LOL
     
  15. JimDawson

    JimDawson Global Moderator Staff Member Director

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    That would be me :) And yes, you will need those parts unless you are mounting the VFD on the head and operating from the VFD keypad.

    As far as speed adjustment, just limit the the Hz range from about 30 to 60. Sometimes it easier to just turn down the VFD for light work like reaming or sometimes tapping. Saves having to adjust the speed on the head when working back and forth between drilling and other operations.

    The parts will also be needed when you convert your machine to direct drive.:grin:
     
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  16. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Rotary Phase Converter
     
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  17. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Okay Jim the old noggin is starting to remember now... Thanks for the input!
    When you say "direct drive" do you mean leave the VFD for the most part static and just use the BP speed controls?

    I don't know why having to use the switches/buttons didn't click in this thread. I was just in the garage with an electrician friend of mine to get a quote to run a 40AMP 220v outlet for my welder, add three new 220v outlets with 3 2-gang 120v outlets next to each of the 220v outlets. I stood right in front of my mill and explained how I have the VFD set up with the switch box.

    All I can say is that if it isn't tough enough getting old, the pain meds I have to take are compounding the senility.:idea:
     
  18. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    As I said... Yes I have read very briefly about them... DOH! They are usually kind of expensive compared to a VFD aren't they? Also, don't you lose about 25% of your rated HP using them?
     
  19. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Yup, I hear what you're saying;)

    Direct drive means removing the mechanical variable speed hardware, and replace it with fixed pulleys.
    http://www.hobby-machinist.com/threads/mill-spindle-direct-drive-conversion.49130/

    No, that's a static phase converter
     
  20. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Thank you!

    Here is the VFD I purchased;


    Electric Motor Wholesale Inc.

    $278.00


    [​IMG]
     
  21. AxeMaker

    AxeMaker United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Ah okay, so I guess I hadn't heard anything about them.
    I can assure you that I will not be converting it to a direct drive LOL. That is way too much work, and, I havn't even got a chance to use the mill yet. I installed the VFD no problem, I just need to finish programming it.

    Remember in one of my other posts where I made the schematic for the table screw extension that I bought? I got the power feed installed to about 80% complete. The extension was sliding back and forth on the screw even with everything installed and tight. So instead of drilling/taping/blah blah I bought some thrust bearings and various shims (so I didn't have to place any more orders) to stop the lateral movement. There is a woodruff key in place to stop the extension from spinning on the screw. It's a cheesy fix, but it was physically easier for me.


    upload_2017-2-15_14-2-21.png
     
    Last edited: Feb 15, 2017
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  22. sanddan

    sanddan Active User H-M Supporter-Premium

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    Axemaker,

    My mill is set up as you are trying to do. I use the VS to set the basic range I will be working in and do fine adjust with the VFD from there. Most times the VFD is at 60 hz but my mill is noisy at the lowest VS speed setting due to belt wear so I tend to move to a spot above that and use VFD to lower the speed from there. A good example of when the VFD speed control us nice is when drilling and then power tapping. It's faster to lower the speed via VFD than to switch to back gears on my mill.

    One thing to be aware of is when you are lowering the speed (using the VS mechanical speed adjust) from say 1800 rpm to 800 rpm you can get an over speed error on the VFD if you try to change the speed too fast. Adding a braking resistor will fix this if your VFD allows it.
     
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  23. AxeMaker

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    Hi Sanddan,

    Thanks for the info! The Lenze has the ability to install a brake resistor & network jack as an option. If I remember correctly the brake resistor is around $14.
     

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