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Thread: VFD Assistance

  1. #1
    Supporting Member jonnydot's Avatar
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    VFD Assistance

    I am gathering materials for a 2" x 72" belt grinder build.I am not sure if my vfd selection would be correct.I have 240v single phase power and the motor I will be using is 2.2 kw (3hp) 2800 rpm 415v three phase (max amp draw 4.39) (link below) .Most VFD's state 220v in 380v out 12 amp (example link below) will these be suitable or do I need to purchase a 240v to 415v vfd ? These units are around $100 odd dollars more and would rather not spend the extra $ Many thanks for reading
    MOTOR LINK ...https://www.ebay.com.au/itm/2-2kw-3-...53.m2749.l2649


    220V to 380V VFD https://www.ebay.com.au/itm/2-2KW-3H...53.m1438.l2649


    240v to 415v VFD https://www.ebay.com.au/itm/2-2kw-3H...4AAOSwvERcIF0k ......This unit is sold buy the same campany that sold me the motor .This is what they said..... QUOTE "you can see our motor can runs at 240V/415V 3 phase. You need to change our motor configuration from Star(415V 3 phase) to Delta(240V 3 phase), then you could use our single phase VFD to run this 3 phase electric motor.

    Please check the wiring diagram at the back of terminal box cover."
    Last edited by jonnydot; 01-31-2019 at 05:57 AM. Reason: Further info

  2. #2
    Supporting Member tonyfoale's Avatar
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    tonyfoale's Tools
    Although I have a nominal 220v supply it always measures at 240 v and I have been running 220 v VFDs for about 15 years with no problems. Some of the 220 v devices actually have a programmable parameter to chose between 220 and 240 v.
    The manuals supplied with the 220v version that you linked to are diabolical, the translation is some of the worse that I have seen. As a result there is a lot of info on the net written in easier to understand terms. Unfortunately a lot of that info is plain wrong.

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    Supporting Member metric_taper's Avatar
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    metric_taper's Tools
    The seller of the motor is ignorant, as they hid the nameplate with their watermark. But I can make out 2 lines, one is for delta and is 220volt connection, the other is Wye at 380v.
    Change the wiring of the motor to the delta connection and you can use the 220 output VFD using your 220v mains. The link to the VFD you attached is not the voltage doubling type.
    Don't confuse yourself with the DC rectified voltage of the inverter, as for driving a higher voltage motor. Or maybe I'm misinterpreting your post. But I've only seen the voltage doubling VFD for 1HP and lower power. The VFD link shows in the Technical features section, indicates;
    Output Voltage Range ---- 0~rated input voltage
    This does not enable a higher voltage motor to be connected. Also my experience is that 200v class VFDs are different then 400v class, and are not interchangeable relative to the mains voltage and motor voltage.

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    Masterjuggler's Avatar
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    I just recently built a 2x72 for myself and went a similar path with a vfd. In my case I have 120V from the wall (American standards are dumb through and through) and a 208V motor, so I took a microwave transformer and rewound the secondary to get the right output. It got pretty warm so I took the fan from said microwave and set it up pointing at the transformer. It's got a 100% duty cycle with the 2HP motor it's running, just gets lukewarm now.

    So two things to note:
    - Neither of the VFDs you linked to actually step up the input voltage, or modify it in any way other than spitting out 3 phase from single at a desired frequency. What you put in, you get out.
    - That being said, the motor you have linked to should be like most good 3-phase motors, in that you can switch between delta and star configurations, which means you can use either high 415V or low 220V. It's hard to tell from that ebay listing because the title, product photos, and description photos all have different information. The second product photo has the label showing 220/380V, where the title says 415. I can also tell you that my 2HP motor scavenged from an old drum sander runs 208-230/480V. If I were you, I'd go with something where you know what you're getting.

    The VFD is more of a preference thing, but for the record I ended up getting this one (clicky). It's working quite well so far, I specifically got one with the potentiometer speed control. The majority of the time the grinder is running, the motor isn't anywhere near stalling, so the VFD doesn't get very stressed.

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    Supporting Member suther51's Avatar
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    I have just entered this near same "jungle" my self. What I have repeatedly come across is to buy a vfd that is oversized to the motor. That said there are bucket loads of contradictory experiences and opinions about these "low end" vfd's some seem to have no problem, others wont give them away to an enemy. Hope your project goes well.
    Eric

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    Masterjuggler's Avatar
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    Suther51,

    I'll admit it can definitely be hit or miss with those cheap Chinese VFDs. Problem is the cost for a "real" one is prohibitively expensive. It's also far better than the next cheap alternative, start/run capacitors. I tried that route and hated it. Can't get full torque, no speed control, have to tailor to the motor, and annoying to use.

    For the application, a 2x72 grinder, it's almost never fully loaded to stall. I haven't been able to stall my 2HP motor even putting my full body weight on it, so a 3HP gives that much more overhead as it is. If it were running a mill or something with constant heavy load it'd be good to oversize the VFD I'd imagine.

    Maybe someone with more in-depth knowledge has differing advice, I'm certainly not the expert on it.

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  10. #7
    Supporting Member jonnydot's Avatar
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    Thanks for your comments guy's I went with this unit ........ https://www.ebay.com.au/itm/220V-Var...53.m2749.l2649


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