Variable Frequency Drives

Discussion in 'Other metal working projects' started by Al2O3, Aug 24, 2018.

  1. Mister ED

    Mister ED Silver

    Exact same thing I did for my lathe. For/Off/Rev drum switch was left in stock location ... now has low voltage wire to and from VFD to control the VFD. The VFD then controls what the motor does.

    All controls for the VFD driven motor need to control the VFD, not the motor. Think of it this way ... any buttons, knobs, etc that you want to turn/push to make the motor do something (on, off, rev, etc) you rewire from high voltage to motor, to low voltage to control the VFD. The VFD then controls the power going to the motor.
     
    Jason likes this.
  2. Denny98501

    Denny98501 Copper

    I have VFDs on both my mills, my lathe and router. They work wonderfully. Not only do you get speed control and reversing, you get programmable slow start and fast stop, single phase protection, voltage and current protection, temperature protection... the list goes on. Skip the rotary three phase connection. VFDs run just fine on single phase 220V power. You won't have to listen to the noisy converter.
    The most important thing to do is to buy from an American dealer that will talk to and help you. There are lots of them on the Internet. VFDs have a hundred parameters that can be set and you won't have clue about what they do and how to set them. Before buying any VFD, download the operators manual and see if you understand it. I have one Chinese E-bay VFD that no one that hasn't set up a VFD before would ever get running. I have a made in India one that has a wonderful manual. The Japanese ones on my Centroid mill and Shopbot are name brand and easy to understand.
    Wiring is fairly easy. Two wires in and three wires out plus grounds.
    Buy one with a speed control and on and off buttons if it is to be mounted on the machine. Other wise, you will need to construct a small control panel with speed controller, reversing switch, emergency stop, and on and off switch.
    Install a power switch before the VFD, You flip this on when you want to energize the VFD. You turn the motor on and off with the VFD controls. Don't turn the motor off by disconnecting the power. You may fry the VFD.
    When you talk to the sales rep, let them pick the VFD. Tell them the HP and voltage and phase. They will set you up with a unit that will supply full motor HP for the electrical conditions that you have.
    You should be able to buy one for $200 to $300. Best money ever spent.
     
    Jason likes this.
  3. Jason

    Jason Gold

    In my short time running 2 VFD's in the garage, I've learned the settings from what I've seen are the same across the board! I got a sales rep up in Canada and he's cool with tech advice for cheap 80buck VFD's bought across scamazon. Wish he was closer so I could buy from him.:D

    I will admit, it was a bit intimidating to me in the beginning, but it's not bad, I had a good teacher too.
     
  4. Petee716

    Petee716 Gold Banner Member

    I did, but it was a pain in the neck until I finally got my head wrapped around it. The manual had all of the information albeit in translated English (I'm being polite), but there was a lot of it. Once I understood the principles of the thing it was ok.
    I still have overloading issues with my table saw. The motor is 2hp 3ph and the VFD is 2.2kv rated for 3hp. My motor is from the mid 60's so it may be underrated as I understand older motors might tend to be. I used the standard over-rating factor of 1.5 as is used for RPC but I think that is wrong. I think the factor for VFD is 2. What size did you end up getting for this application Kelly?

    Pete
     
  5. Melterskelter

    Melterskelter Gold Banner Member

    The documentation and support for VFD’s varies dramatically. I bought my first one from AutomationDirect and recommend them having bought three VFD’s from them. The ring-bound manual is well illustrated and very clearly written. I set first VFD up on my mill in a few minutes using the manual. I also had a couple subsequent more technical setups and I promptly got clear accurate information from their tech department immediately when I called. They will answer your debating questions. I believe that derating mainly applies for VFD’s intended for 220 input being supplied with 120. But that really is beyond my pay grade.

    They are not the cheapest and far from most expensive.

    I also bought a cheapie and set it up. The manual was written originally in Chinese and poorly translated. I got it done, but it helped to have done a few previously.

    This may not be a place for the best investment of time to save 30 bucks.

    Denis
     
    Last edited: Dec 1, 2020
  6. rocco

    rocco Silver

    Some of us are closer, how about his contact info? I don't know that I'll be needing one any time soon but I can easily see a VFD in Jeff's future.
     
    Last edited: Dec 1, 2020
  7. ddmckee54

    ddmckee54 Silver

    Derating is required when you connect a VFD intended for 3 phase input to a single phase source. It can be done, but there are drawbacks. Single phase is less efficient than 3 phase for driving a motor, the square root of 3 times less (1.73). Most engineers will just round this up to 2 and use that as the de-rating factor.

    It kind of sounds like the translated specs were based on a 3 phase input source for the VFD, the performance numbers for the VFD are more impressive that way.

    Don
     
    Melterskelter likes this.
  8. crazybillybob

    crazybillybob Silver Banner Member

    +1 ^ What Don Said.^
     
  9. garyhlucas

    garyhlucas Silver

    It was mentioned earlier that feeding the VFD with single phase only two sets of diodes are used at a higher current input as well. However that is not the big issue. The biggie is that DC from 3 sine wave phases 120 degrees apart has very little ripple. On single phase which is just one sine wave the ripple is huge and the filter capacitors take a real beating. The better VFDs, I happen to like the Hitachi line, have replaceable capacitor banks as that is the shortest lifespan part. This is what really requires using a double sized VFD to run on single phase.

    At my last job I put a VFD on our 2 hp drill press. I installed a foot switch with a 3 position toggle switch. In one position the drill ran normally when you pressed the foot switch. Center was off and in the other position the press started up running in reverse without using the foot switch. Put the tap in the hole running in reverse. Press the pedal and comes to a stop and goes in forward tapping the hole. Release the pedal at the bottom and the tap backs as it goes into reverse. Morse taper spindle takes the inexpensive morse taper tap collets too. Worked great, we did a lot of tapping.
     

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