VFD explain it like I知 5...total noob.
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    Default VFD explain it like I知 5...total noob.

    Hello, first post, a little lost. I have a new-to-me Siber Hegner RB1. I致e read and watched a lot of VFD related stuff on the web and I thought I壇 just post what I have and ask a simple question.

    I have 220 single phase available. Purchased a Hitachi and random EBAY brand VFDs for 3hp 3 phase. My motor is 3hp.

    The motor is wired into a back panel that feed several controls and switches. Question: I can I simply wire the VFD to the 4 wires coming out of the panel? I知 reading yes and no. Mostly mentioning VFD wires direct motor. I have a second 3 phase control motor only 1.5hp I think, but 3 phase. Is that a 2nd VFD? I知 hoping photos show below.

    57ebe5b1-babb-49a5-94db-13c08c6a56fa.jpg732e00b5-c207-4c52-8832-00318efa6e74.jpg732e00b5-c207-4c52-8832-00318efa6e74.jpg95cd75c7-914f-4040-ad20-43c654383e6d.jpge4793277-7f69-41f3-b801-784483b1f221.jpg32b066eb-d4ac-49bd-9d2a-daa313d2bef5.jpg

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    Hi Evil...

    So... without knowing what that 'panel' contains, or how it's wired, I'm going with the 'safe' answer:

    Wire the motor directly to the VFD.

    The panel probably controls the motor using across-the-line starting with contactors, and provides protection using motor overload features. The VFD handles all this as part of it's programming and synthesis.

    You will want to control the power to your VFDs with contactors. The 'standard' technique is to have a main contactor that uses a 'START' pushbutton, and a 'STOP' pushbutton, where when you press the START button, the contactor pulls in, and once in, an auxiliary contact of the contactor causes the contactor coil to stay powered after the START button is released. The STOP button has a normally closed contact wired in series with the aforementioned auxiliary contact, pressing it opens the 'hold' circuit, causing the contactor to drop out.

    This contactor's output goes not only to your VFDs, but also to an isolation transformer to provide power for things like lighting, table feed motors, and a DRO system. On MY machines, that isolation transformer also provides AC power to run constant-speed cooling fans atop the spindle motors, as I've removed my spindle motors' cooling fans. When using a VFD, it's common to run the motor very slow for some operations, and the spindle motor's cooling fan, turning slow, provides very little cooling air. Running a constant speed cooling blower keeps the motor cool regardless of speed... and I also program my VFDs to go to at LEAST 120hz (twice motor speed). High speed on the motor causes those fans to howl like a fire engine siren... ;-)

    Find out what that panel has in it!

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    Quote Originally Posted by DaveKamp View Post

    Find out what that panel has in it!
    Thanks. This helps. I'll pull the panel tomorrow. I think I'm going to have to buy a branded VFD with a good manual. The ebay stuff I have has terrible manuals.

    Eric

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    I have a 3phase power head. That's a 2nd VFD then right?

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    Each VFD can produce only a single frequency and voltage (motor speed). So anything that needs to run at some other speed is going to need a different VFD.

    Generally, it is one motor, one VFD.

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    Do you need to upsize the VFD to use single phase input? Or is that generally for over 5hp or so?

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    I've read that other places in my searches. No experience.

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    Quote Originally Posted by Rob F. View Post
    Do you need to upsize the VFD to use single phase input? Or is that generally for over 5hp or so?
    Generally not if you are buying new properly sized VFDs. Buy a brand name unit which will clearly show single phase input ratings. Teco, Hitiachi, GE and others all have 220 single phase rated VFDs that do NOT need to derated. And they are reasonably priced. If however the VFD is rated for 3 phase input only then it would need derated. However some of those have phase loss protection features. In that case that feature would need disabled. I highly recommend you stick with one of the brand name units designed for single phase input. They also tend to have better documentation and very good community support here.

    Sources for VFDs
    Electric Motors | Motor Controls | VFD | AC Drive
    AutomationDirect | The common sense way to buy industrial controls
    AC Drives | DC Drives | Variable Frequency Speed Drives | VFD

    If in fact you have multiple motors to run and you don't need variable speed control then this is an ideal scenario for a rotary phase converter (RPC). An RPC can run multiple motors/machines at the same time and you don't need to rewire or gut the controls.
    Phase Converters | Power Transformers | Power Accessories | American Rotary
    Last edited by Ohio Mike; 04-13-2019 at 09:25 AM. Reason: add info

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    Quote Originally Posted by DaveKamp View Post
    ...
    When using a VFD, it's common to run the motor very slow for some operations, and the spindle motor's cooling fan, turning slow, provides very little cooling air. Running a constant speed cooling blower keeps the motor cool regardless of speed... and I also program my VFDs to go to at LEAST 120hz (twice motor speed). High speed on the motor causes those fans to howl like a fire engine siren... ;-)

    Find out what that panel has in it!
    Possible that most or all of the stuff in the panel can be replaced by the VFD so the request for what is inside is spot on.
    Also the low speed cooling is on but usually only for long duty and such machines often only see very short spindle run times.

    The twice speed (120HZ) can be a problem on lower cost motors. The first is balance and vibration. The second is bearing wear which is a square of the speed so twice as fast is 1/4 the life.
    In high gear or top speed you can not run the spindles in such machines at 2X normal. The spindle bearings will not like this for any amount of time.
    The bigger one is the guts letting go due to centrifugal force. Once you create such an explosion you will not forget the lesson learned.
    I now worry at anything above 125% the design speed, will do 150 if tested, 200% means serious looking at the engineering.

    Many use a VFD in place of a rotary phase convertor on the outside or input side to do the single phase to three thing.
    But if the control panel has pull in relays or other things it controls like a coolant pump you have to keep it set a 50-60hz which wastes a lot of the VFD capabilities.

    So yes it's about what is inside the panel and why it is there.
    You can rewire the spindle start stop buttons to the VFD. Hard current limits such as fuses or breakers should probably stay in place so this is not a 5 year explanation or task.
    Good VFDs come with manuals. If you are not a controls engineer reading them is so very hard.

    Just a really rough type end. If your VFD will light up with single phase input then yes you can set it for 60hz and put it on the main machine inputs and use it as 3phase power from the electric company.
    A VFD takes incoming AC power, turns it into DC (straight line) and the chops this up on it's output side to sort of make the new AC or the sine waves needed.
    Why do you see overate power levels as a standard recommendation? A single phase input only gets to use a part of the input circuit so that limits how much power can be carried before things go up in smoke when you make that DC bus.

    I don't know how to make this simple.
    Assuming the machine has only a spindle to run run you can live fine with all sorts of options.

    I have never tried the second motor VFD in front of the mains one. I would think ok but wonder.
    Anybody cascade these things down a chain? You go back to DC but is the second a happy camper?
    Bob

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    Quote Originally Posted by Ohio Mike View Post

    If in fact you have multiple motors to run and you don't need variable speed control then this is an ideal scenario for a rotary phase converter (RPC). An RPC can run multiple motors/machines at the same time and you don't need to rewire or gut the controls.
    Phase Converters | Power Transformers | Power Accessories | American Rotary
    Thanks everyone for the comments. This helped sort bits and pieces I read on the web. Considering I have two 3 phase motors (1.5hp on the powerhead), and I really don't want to modify the back panel...I'm going to contact American Rotary and spent the money. I got a great deal on the mill. I don't want to be cheap on the install.

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    Quote Originally Posted by Rob F. View Post
    Do you need to upsize the VFD to use single phase input? Or is that generally for over 5hp or so?

    What Ohio Mike said, to start with.

    But, it is possible that there is NO effective derating that will allow some VFDs to operate n singe phase.

    Some newer VFDs use no large capacitor on the bus, using instead, a film type of smaller capacitance really just for basic filtering of high frequencies. I designed one like that for a MIL use running on 208 3 phase, where the -40F/C requirement was unrealistic for electrolytics considering the space available and the size that would be needed, and the lifetime requirement was rather long. (it was a semi COTS procurement, and the true OTS part would not work, so we did the new design)

    Later, when the client requested a single phase input version, an outboard set of good electrolytics had to be added. And that version did not have the -40C rating.

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    Well update. Mill is running great with a 7hp static phase converter. The rotary phase converters called for 10hp and the cost was approaching what I paid for the mill. No to make something...

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    Quote Originally Posted by evl View Post
    I got a great deal on the mill. I don't want to be cheap on the install.
    You do realize the static converter was cheaping out? Well now that thats done I'll explain the VFD like you were 5, "Get your grubby hands off that before you break it!"

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    Quote Originally Posted by evl View Post
    Thanks everyone for the comments. This helped sort bits and pieces I read on the web. Considering I have two 3 phase motors (1.5hp on the powerhead), and I really don't want to modify the back panel...I'm going to contact American Rotary and spent the money. I got a great deal on the mill. I don't want to be cheap on the install.
    American Rotary's tech support is awesome. Not realizing what time zone they were in, I called their support number early this week after hours (Eastern Time) with a question about my RPC. I got Susan (I think), who was driving somewhere. She was very knowledgeable about their products and their capabilities, and even found a place to pull over when she had to look something up, which took only seconds. When I need another RPC, they're first on my list.

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