Using a VFD to run a 200HP 3ph motor with home single phase and a household extension
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    Default Using a VFD to run a 200HP 3ph motor with home single phase and a household extension

    My friend and I used a 100HP VFD to spin up and idle a 200HP motor.
    We used a transformer to step up the voltage to 460V and ran that through a regular home extension cord (14ga or 16ga) as the input power into the VFD. Itís the orange cord toward the end of the video.
    We soft started the motor with a slow ramp, but we were able to drive the 1750RPM motor up to 80Hz/2400RPM.
    You can see the VFD panel showing the frequency and RPM.

    The motor was obviously unloaded other than the significant energy the motor fan used to swirl air. Even at 460V, 14ga is only able to carry about 9KW or so.


    YouTube

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    Where's it show the 200 HP motor? ……...the camera was that close it could have been 2 HP

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    Quote Originally Posted by Limy Sami View Post
    Where's it show the 200 HP motor? ÖÖ...the camera was that close it could have been 2 HP
    The camera wasnít that close...




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    That is really cool. Definitely opens up bigger RPC options if you can get that spinning up without capacitors.

    With the amp draw as low as it was there could you get away with a much smaller VFD just to spin it up? Like a 10 or 15HP? Get it up to 60HZ on 3 phase then simultaneously drop out the VFD and close a real big contactor to drive it on single phase.

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    Quote Originally Posted by Garwood View Post
    That is really cool. Definitely opens up bigger RPC options if you can get that spinning up without capacitors.

    With the amp draw as low as it was there could you get away with a much smaller VFD just to spin it up? Like a 10 or 15HP? Get it up to 60HZ on 3 phase then simultaneously drop out the VFD and close a real big contactor to drive it on single phase.
    You could definitely use a smaller VFD to spin it up.
    Youíll only be able to generate whatever power your supply line current will give you, minus idling power and other losses.

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    Unreal!! I never would have thought it possible.

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    Should have stepped it up to 600 volt.....

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    Quote Originally Posted by digger doug View Post
    Should have stepped it up to 600 volt.....
    VFD was 400-500V input.

    In theory, we were already over the insulation rated voltage (300V, I think) for the cord already.
    In reality, Iím sure it would hipot test probably over 600V anyways.
    Next time Iím at his place, Iíll look up the voltage on the cord.

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    I found the motor at a scrap metal place and it had been sitting outside for quite some time.
    I actually seriously considered buying it and using it as a RPC, as the rotor inertia alone would handle large current surges.
    Instead, I told my friend about it and he bought it to add to his large and varied collection.

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    If you do it again, hang an amp-clamp on the feed and let's see what the current draw looks like.

    Sent from my SM-G973U using Tapatalk

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    Quote Originally Posted by Cole2534 View Post
    If you do it again, hang an amp-clamp on the feed and let's see what the current draw looks like.

    Sent from my SM-G973U using Tapatalk
    VFD display shows the current draw right on it.

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    Quote Originally Posted by rpseguin View Post
    VFD display shows the current draw right on it.
    So what did it draw?

    N/m, rewatched vid. 9.4A

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    Got an IR camera, even one of the apps you can load onto a smartphone? It would be interesting to get an idea of the extension cord temperature the next time you try this, especially if there's hot spots.

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    Default Using a VFD to run a 200HP 3ph motor with home single phase and a household extension

    We have FLIRs at work, but donít think I can take them home.
    Anyhow, the motor is down at my friends shop now, amidst a large collection of motors, from tiny to much larger than 200HP, and some jet turbines including a F104 Starfighter GE J79 with afterburner, ...

    I guess we could rerun the experiment, this time with actual lighting so you can actually see stuff, instead of flashlights in a driveway. :-)

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    Sounds good. Some video would be interesting.

    A Starfighter engine? J79's are so plebeian. Let me know when when your buddy gets hold of a J58...

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    Default Using a VFD to run a 200HP 3ph motor with home single phase and a household extension

    Quote Originally Posted by Milland View Post
    Sounds good. Some video would be interesting.

    A Starfighter engine? J79's are so plebeian. Let me know when when your buddy gets hold of a J58...
    He has several other large turbines, but no J58s

    My day job is for the Space Systems division of the company that built the airplanes that used the J58Ö
    Let me see if I can put in a parts requisition to the SkunkWorks for some J58s and see what shows up in my cube. Pink slip for sure! :-)

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    Quote Originally Posted by rpseguin View Post
    You could definitely use a smaller VFD to spin it up.
    You’ll only be able to generate whatever power your supply line current will give you, minus idling power and other losses.
    Difference between 2hp VFD and 200hp VFD with limited supply is that the large VFD can supply enough current/torque at low voltage (low frequency) to start even hugomongous motors but tiny VFD hits the output current limit.

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    Quote Originally Posted by MattiJ View Post
    Difference between 2hp VFD and 200hp VFD with limited supply is that the large VFD can supply enough current/torque at low voltage (low frequency) to start even hugomongous motors but tiny VFD hits the output current limit.
    Right.
    I meant smaller than 100HP :-)
    I didnít look at the startup current when we were soft starting (it was a long ramp up), but letís assume it was no more than 20A (or we would have had a very hot or melted cord).
    20A x 460V = 9200W, so about 12HP.
    Scale that for single phase derating, so maybe 20-30HP VFD would do the trick

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    Quote Originally Posted by rpseguin View Post
    VFD was 400-500V input.

    In theory, we were already over the insulation rated voltage (300V, I think) for the cord already.
    In reality, Iím sure it would hipot test probably over 600V anyways.
    Next time Iím at his place, Iíll look up the voltage on the cord.
    If you put an RF spectrograph on it, you'll probably see HF noise in the realm of over 600v with regularity. I would not be surprised to see the cord survive it, but once it starts leaking a little bit, it's all over...

    The only thing that 'prevents' a VFD from being able to do this kind of thing, is the programming. the circuitry and circumstances really are not complicated... if there's high enough rail voltage in the inverter to allow the thyristors to fire, you'll have output current.

    The idea of using it somehow, really comes down to some simple circumstance- by spinning up a high inertia object, you have a substantial amount of kinetic energy stored- you COULD use the big motor, even with more flywheel attached, to drive a nasty intermittant mechanical load, like a drop-hammer... or an inertial log splitter, or something like that... something you would NOT want a body part to get caught in...

    You could also use it to control some extremely light mechanical load that needed to have EXTREMELY stable running speed... the VFD's internal oscillator would set the running frequency, and once that big flywheel inertia was spinning, it would NOT want to change speed anytime soon...

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