VFD Question

Ok I need to put a 3 phase converter in to run my mill.
If I use a static converter I will only have 2/3 HP with a 1HP motor.
If I use (or make) a Rotary converter that will solve the HP loss, and I have a 3 HP motor on my floor but the Money (or time and parts) my be the same as a VFD
Now I see these VFDs on Ebay for $150. If I use a VFD do I loose power assuming I am running at 60 cycles? Can I put a plug on the output to plug in EITHER my lathe, mill or whatever else I what (provided its within the rated output)?
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Wayne wrote:

Agreed, and the versatility advantages of a VFD far out weigh the rotary, even if the rotary only costs 1/2 as much.

You don't lose any power, however most VFD's need are de-rated if running on household 220v. If you're putting 220v single phase(2 phase, depending on your point of view) in and want 220 3 phase out you need to double(approx.) the size of the VFD. IE: 2hp rated VFD for a 1HP motor.

Sure can, I do it every day, mine's actually hard wired, works fine as long as the switch at the machine is used for on-off. You may also find that you want to wire it up for remote control of speed or on/off, which can also be done at both machines.
Tom
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There is no power loss when running at 60 Hz. You can use a single VFD on multiple machines provided the motors are similar in rating, although this is not the preferred arrangement. You cannot use the original motor switch or contactor to start the motor when driven from the VFD as it will trip if you try it. This means that you need a set of VFD remote controls at each machine unless you rig up a portable control station to move from machine to machine. There is no need to buy an oversize VFD for running from a single-phase source provided the VFD is rated for single-phase input as the vast majority of small units are nowadays.
Randy
"Wayne" <makowicki> wrote in message

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I'm using the original motor switch on a Clausing 5914 to start, reverse, & stop the motor via a VFD. The switch is wired to the VFD inputs, though, and I suspect you meant that the power leads from the VFD cannot be wired through the switch. That is a big no-no, from what I've read.

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This is an interesting topic. I am an electrical project engineer at a nuclear plant... we are replacing some huge motor-generator sets with a couple of large Robicon VFD's. They are rated at 10,000 HP each, not exactly something you'd find on eBay. Used to power the reactor recirculation pumps for a boiling water reactor, appx 1100 megawatts. The VFD's will be capable of about 700 amps output at 4160V, the outbound cables are 750MCM and there are three such conductors per phase.
An interesting project, the largest single project I have ever worked on. I am involved on the field work side and craft work, and of course correcting all the screwed up design we were given.
Dave
"Wayne" <makowicki> wrote in message

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Wayne wrote:

The overcurrent protection parameter will only be correct for the largest motor. Other than that, you will need a three wire cable from the start/stop station to the appropriate low voltage control terminals in the VFD. This doesn't provide the almost sure-fire interlock of a start/stop in line with the holding coil, but it seems pretty reliable for my personal shop use. If you want to reverse from the machine, you'll need additional control wiring as well. The newer small VFD's are rated for single phase input, but many of the vintage units on ebay have to be derated, like the AB 1305's I use. Check the input voltage and model # carefully, a lot of the ebay VFD's are for 380+ volt input. The major manufacturers have pretty good documentation online. As others have pointed out, the VFD output leads have to go right to the motor leads, with no contactors or switches in between.
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I have seen many of the Baldor units going for $100 to $160 these are the 1 HP 2 HP models. So I have to remove the many electrical boxes on my machine no big deal. It sounds like you want the magnetic control before the box no big deal. Now some say they can run single phase output also that sounds nice but how well does that work at the slower speeds? I would most likely run my mill motor (3 phase) at or near 60 cycles and still do the belt changes. But I do have a motor that is single phase that runs a hydaulic pump that I would like to slow down to 40% of normal speed, will that over heat the motor? Or should I just send the money for a hydraulic speed contol also?
I hope I am not asking more than I am I giving but I will have an I Owe You
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Wayne wrote:

I'm not aware of any way to use a conventional VFD to control the speed of a single phase motor. The magnetic control is not used at all, only the start/stop box. The start/stop box wiring to the old contactor is pulled out and goes straight to the VFD terminals. Momentary make of one terminal with the common wire starts the motor, breaking the normally closed contact of the stop button stops the motor. However, this is all done by the VFD's electronic control, not as simple as cutting off the power to the holding coil in the conventional contactor (although I have seen contacts weld together and continue to energize a motor with no holding coil power, so I guess nothing is foolproof.)
I would recommend buying a 3 HP (after derating) VFD if you're only getting one, that will run a Unisaw or most any machine you may end up getting. Patience is a virtue, especially on ebay, with a little time, you should be able to get a decent deal.
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