Low power - motor or VFD?

Discussion in 'Tools' started by datosi81, Mar 10, 2018.

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  1. Mar 10, 2018 #1

    datosi81

    datosi81

    datosi81

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    Managed to get the SAIMP mill situated where I want in the garage finally and Hooked up the VFD and had the motor spinning as expected on the bench.

    Earlier today I went to reinstall the motor on the head and get the pulley setup etc. after getting it hooked up and the belt on, the motor wouldn’t spin regardless of frequency. I pulled the motor back off and bench tested it. With no load on it, the motor seemingly responds as expected related to the frequency. I tried grabbing the shaft from a standstill and powered it up and was able to hold the shaft still with almost zero effort. I understand the motor may lack torque at lower frequencies but this seems like a real issue. I’m wondering if the motor is bad since I never ran it before to test it. Or is my cheap eBay VFD bad? Or am I using the VFD wrong and there is some setting I don’t know about that needs adjusting? The motor is labeled 1hp 1750rpm 3 phase. My VFD is powered by a 20amp 220v single phase line, outputting (hopefully) 220v 3 phase.

    I have worked as an electrician many years ago for several years but admittedly never really did much with 3 phase, so my knowledge on that subject is just what I’ve learned online. My understanding is it doesn’t matter what phase is wired to what wire on the motor, but that doesn’t mean I’m correct lol. Or perhaps there is a setting in the VFD that needs to be changed. I’m leaning toward the motor simply being weak/worn. Any advice is appreciated
     
  2. Mar 10, 2018 #2

    Nick Hulme

    Nick Hulme

    Nick Hulme

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    Is the motor dual voltage? if not it's likely you're running it at half it's rated voltage.
    If it is dual voltage how is it wired, Star or Delta?
    Your VFD should always be set up with the data from the motor plate entered in the appropriate parameter settings.
    Make, model and data plate photos always help and save others who would like to help guessing the missing info,
    Regards,
    Nick
     
  3. Mar 11, 2018 #3

    datosi81

    datosi81

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  4. Mar 11, 2018 #4

    Nick Hulme

    Nick Hulme

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    VFD make and model?
    How did you set it up?
    BTW I have a lathe, drill press, two mills and a tool and cutter grinder running on 3 phase motors with VFDs, 3 Siemens, 1 Hitachi and an Omron, the first thing I do is download the manual for the VFD, the second thing I do is buy the VFD ;-)
     
  5. Mar 12, 2018 #5

    Wizard69

    Wizard69

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    It is never a good idea to grab a hold of a motor shaft no matter how low the apparent torque. If the motor decides to startup it will tear your hand to pieces before you even realize it. If you want to see if a motor is developing torque us a block of wood to rub against the shaft. I don't want to sound like I'm preaching but safety is often overlooked at home.

    The second thing to do is to set the drive up to run at the motors standard parameters, most likely 240 VAC @ 60 HZ. If no torque is developed at this value then I would make sure he drive is set up right first and second make sure the motor is not running single phase
     
  6. Mar 12, 2018 #6

    xpylonracer

    xpylonracer

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    You say you have linked 4,5&6 but have you also linked 1-7, 2-8, 3-9 and supply in at 1,2,3 ?

    Emgee
     
  7. Mar 12, 2018 #7

    datosi81

    datosi81

    datosi81

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    Xpylonracer - yes, that is how I have it wired. Sorry I should have specified.

    The vfd is a generic eBay HY or huanyang I believe is the spelling, 1.5kw. The instructions are very basic. Some of the literature I’m finding online show parameters for most vfd‘ into the 140’s or 150’s. The instructions with mine only go up to the 30’s. So I’m not sure if the parameters are the same meaning “Pn003” is the same as “Pn003” from a booklet I find online.
     
  8. Mar 12, 2018 #8

    Aries37

    Aries37

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    I think more diagnostics are neede here to find your exact problem. If you have the motor leads connected together as shown on the motor nameplate and those resulting three leads connected to the VFD per the instructions and it still doesn’t run correctly, take the motor to your local motor shop and have them “megger” the windings. That’s a high resistance test applied to the windings that will determine if their is moisture plus insulation condition, etc. If it passes that test have them run it on true 3 phase power. If it passes this test you know the motor is good. Then you’ll know your problem is with your VFD or the wiring to it. I would not purchase used electrical components like this from eBay that often come without complete instructions or a warranty. Purchase from a reliable distributor that provides warranty and tech services should they be needed. I have several VFD’s that have been running in my shop for many years with zero problems and all purchased from the same vendor. I can supply the name should you choose to proceed further.
     
  9. Mar 12, 2018 #9

    datosi81

    datosi81

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    Thanks for the feedback. The vfd is brand new, it’s just the instructions are limited, offering info on the first 30 or so parameters for some reason.

    I agree I need to get the motor tested. I’ll have to find a motor shop in the area. I think if nothing else, as you suggested, hooking it up to true 3 phase would tell the story.

    If it ends up bad I’ll need to decide if I should get another 3 phase or just pick up a single phase and rely more on belt changes...it seems the price difference isn’t that significant.
     
  10. Mar 12, 2018 #10

    Aries37

    Aries37

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    The nameplate on your motor states a 182 frame size plus it appears to be totally enclosed as well. That style in a 1 hp tells me that it is probably special for your machine as most replacement standard 1 hp motors do not come in that size frame. Keep in mind that the frame size determines all critical dimensions like shaft size, mounting hole dimensions, shaft height center and other critical info.
    You can have your motor re wound if it does not check out. Re winds are expensive due to nigh copper prices, but in the case of a special mounting its the best way to go. Also keep in mind that some replacement motors are not VFD “friendly” which means they are not wound with the correct wire and insulation to withstand the abuse the VFD imposes on the windings. Your existing motor is definitely one of the old ones with lots of iron, heavy construction, wiring and bearings that will operate without problems.
     
  11. Mar 12, 2018 #11

    datosi81

    datosi81

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    Yeah I don’t know how old it is, but it sure is heavy! I’d guess approaching 100lbs which seems like a lot of weight for a 1hp motor. I know it’s definitely not the original motor as there is a funky adapter plate someone attached to it to get it to bolt to the machine View attachment IMG_1983.jpg
     
  12. Mar 12, 2018 #12

    Aries37

    Aries37

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    I’ve seen this setup before. Using a non-standard motor for a mill, then modifying it by adapting a flange plate to mount it. In most cases it can be done, so at this point I would proceed to get the motor checked out at a motor shop. With that diagnosis you can decide the next step. Your motor was built by Louis Allis, no longer in business, but well known for quality and longevity even if overloaded. The weight is due to an all cast iron frame, heavy stator laminations and a well designed and built rotor assembly. Keep us posted on your results.
     
  13. Mar 15, 2018 #13

    Nick Hulme

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    Not all old 3 phase motors work properly with VFDs, the gear motor that came on my on my Rapidor Manchester power hacksaw wasn't compatible with a VFD, it turned but just not with the right speed or torque, the 3 phase 2 speed motor that came on my FB-2 mill head just generated some smoke :D
    Fit a nice modern flange mount motor and dump that Hunk-O-Junk!
     
  14. Mar 16, 2018 #14

    datosi81

    datosi81

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    I contacted a reputable motor service/dealer in my area and spoke at length with the head technician. He said I could bring it in and test it, but, to Nicks point, he feels confident it’s not compatible with the vfd and estimated the motor to be late 60’s vintage at the youngest, if not older. So now I’m kicking around different ideas on motors. I already bought the vfd so I might as well get a 3 phase.

    Another point the tech made is that he feels the vfd is probably too small for anything other than 1hp-ish. I told him the vfd I bought is rated 1.5kw so I felt it should be good to 2hp but he said the rating is likely optimistic, plus since the vfd is single phase in, 3 phase out, its rating is probably even lower, being rated for 1.5kw with 3 phase in and out.

    So I gotta figure out in the next few days what I’m gonna do. I am supposed to go look at a lathe in a few days that is 3 phase, so I could be in the same boat there. But I’m thinking if that motor is small enough, and new enough, I may be able to utilize the current vfd for that if it works out and just get a larger one for whatever motor the mill ends up with.
     
  15. Mar 16, 2018 #15

    Aries37

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    I would get the motor checked out, then you’ll know if it’s OK. On the VFD issues, I’m using several of them on old frame motors for years with zero problems. I use GS 2 AC micro drives purchased from automation direct.com.
    My mill is a Lagun, many years old with a 2hp 3 phase motor. The drive I’m using is rated at 230 volts single phase input, 230 volt 3 phase output. This drive is rated at .5 to 3 hp. Any motor over 3 hp requires 3 phase input power. So in that application your source would need to be true 3 phase or else a rotary generator. Static type converters are some times problematic and not recommended for a VFD drive setup. Also I’m using input and output load reactors which are very important for operating older motors not rated for VFD use. All of this is installed in a control cabinet with proper line side fuses, etc. One of the nice features about this brand of drive is that the control faceplate is detachable with a proprietary cable so you can mount it conveniently on your lathe or mill. Another crucial point here is proper size wiring to and from the VFD. Long runs have voltage drops and therefore I typically go one size bigger on wire size than specified. Another issue is that torque ratings drop off considerably when the motor is operated at low rpm’s. In this case simply changing belts to a different pulley ratio solves that problem. Finally, there are a lot of design parameters that go into selecting and wiring up a VFD for correct operation.
     
  16. Mar 16, 2018 #16

    Nick Hulme

    Nick Hulme

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    All that might be true for "Unknown Warrior" brands from the far east, my Siemens, Mitsibushi, Omron and ABB drives are all good for at least their plated ratings, even in adverse applications.
    Two old 1hp Siemens Vector Drives I use on my lathe and power hacksaw have been continuously powered and in use for 15 years or so and were ex-industrial second hand units when I bought them ;-)
     
  17. Mar 16, 2018 #17

    Wizard69

    Wizard69

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    VFD's and 3 phase motors are probably one of the best improvements one can make to a machine tool for the money involved. Variable speed is very useful and the other features modern drives have like soft start can lead to longer machine life.
    I'm going to suggest that the tech is full of crap. Unless the manufacture is engaged in fraud it should be able to do what is says on the spec sheet.

    You will see drive derating when you try to run a 3 phase in drive on single phase input. This can happen with a combination of factors but primarily involves the rectifier on the input side of the VFD. It is completely possible for a 3 phase drive to have a bridge rectifier that is sized for 3 phase in but can't handle the current demands for single phase in. An applications engineer can usually help with finding a drive that can run properly on single phase in.

    These days though single phase 'in' is so popular that most drives under 5 HP rating have specs for operation on single phase. The ratings are accurate with most manufactures, they pretty much have to be for liability reasons.
    Speaking of larger motors if you do re-motor and go the VFD route it is usually a good idea to uprate the motor a bit. The reason is pretty simple as you vary the motors RPM the ability for that motor to produce power and lower rpm's GOES DOWN! Thus going with a larger motors, for example a 3 HP in place of a 1 HP, gives you more useful torque over a wider range of speeds.

    In any event I come back to the idea that you must have something wrong someplace. If you set the drive to 60 hz the motor should perform in a way similar to across the line operation. After all (assuming a 60 Hz country here) the operating conditions are the same. As such I'd review your drive settings again.
     
  18. Mar 17, 2018 #18

    datosi81

    datosi81

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    USA here, PA to be exact. So yeah, 60hz.

    If I had to do it over again I would have got a larger VFD to begin with. Even if the 1.5kw I have is sufficient for a 2hp motor, I would likely get a 3 hp replacement. I don’t think returning it is an option as I stupidly tossed the box and the seller on eBay “vanished”. When I go back into my purchases, that item is blank, so who knows?

    I do tend to agree something is wrong. The tech seemed knowledgeable but I don’t really buy that the older motor “just wont work”. I would think if there was a downside to a vfd on an old motor it’d manifest as possibly shortened life, not it not working altogether.

    I also agree the vfd settings could be off. It seems my instructions don’t have all the parameters listed though and that is part of the problem. My thought is, and if I’m using the wrong terms forgive me but hopefully you guys know what I mean, the ramp up time is the issue. If there is a way to set the vfd almost like it we’re connected on a regular 3 phase with a contractor switch, I think the motor would be making the torque needed to “get going” with load on it. It’s almost like it makes next to zero torque starting and ramps up, which I get the reason for that, but to an extreme that stalls the motor with the slightest of loads, preventing it from ramping and ever getting to a usable torque. Hopefully that makes sense.

    I’m also gonna make another thread about the lathe I looked at today....limited info on it online so it could answer some questions about what to do on the vfd front with the mill.
     
  19. Mar 17, 2018 #19

    Aries37

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    I’ll jump back into this problem again and recommend that you get the motor tested at your local motor shop. If it’s OK then you can deal with the VFD and wiring. I’ve done lots of VFD work and can tell you that most older motors work the best with no problems, if installed correctly. That includes the wiring to and from the VFD and the correct VFD selection. Most VFD’s allow for a gentle ramp up to full speed along with dynamic braking so you can bring the machine to a quick stop. Without complete instructions from the manual, it’s probably impossible to get the parameters correct. Again my reference to purchasing from a distributor that can size a unit to fit your application plus offering tech services should they be needed.
     
  20. Mar 18, 2018 #20

    MachineTom

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    I agree you likely have a wiring issue. Start at the beginning, with voltmeter, is there 220 at the input terminals, hooked correctly. next while running on the bench output voltage 220, each wire to the correct connection on the motor, remove each wire nut and check the wire conductor is wound with the others. I have had the conductors slide back when installing the nut, losing contact and driving me nuts.

    Recheck the pairing of the wires, note 2, 7, 1 are sometimes misread leading to issues. lastly the parameters, is the FLA parameter set for a 1hp motor, is the output voltage selected
     

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