VFDs and line reactors questions

To all youse high speed spindle guys, I have now a new 2.2KW VFD and matching 24000 RPM spindle motor. I am wondering how important line and load reactors are for this setup.
Especially the line reactor because the motor/VFD combo is supposed to be matched and because the motor wires will be short, 6 feet or so. From looking online I have determined that a reactor rated at 12 amps, 2.5 mh, and 5% impedence is optimal. Can a reactor with a larger current rating be used? Also, since the VFD can be connected to single phase power and I want to use that option, I think I need to use a reactor with a higher current rating. 18 amps instead of 12, right? I haven't seen any single phase reactors yet on ebay which is why I am asking. On the output side I am concerned with noise making problems for the CNC mill (a Fadal 15XT) that the spindle will be installed in. Will a reactor help with this sitaution? Do I really need one with such a small (2.2 KW) motor? Thanks, Eric
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snipped-for-privacy@whidbey.com wrote:

I'm not sure a line reactor, per se is what you need. it does help in large installations, where dozens of large VFDs cause harmonic problems on the mains. Do you actually HAVE a problem with line interference?
I had some problems here, mostly hash on my computer screen when the VFD was running. The fix was to put a line filter unit on the power input to the VFD. This contains a combination of inductors and capacitors, and is specifically designed to eliminate interference from equipment getting out on the mains - and vice versa. These are often installed at the power entry of various electronic gear, large computers and things like that. I have a few in my junk box.
Here's one : http://www.ebay.com/itm/380905940894 You might be able to find one closer.
Jon
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wrote:

I have as yet not powered anything up but have read about problems, one of them being drives failing from power surges upon powering up. Apparently a line reactor helps to prevent damage from current surges upon powering up. Eric
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snipped-for-privacy@whidbey.com wrote:

VFDs should be desinged to handle the inrush surge. Small VFDs may use NTC thermistors or resistor/SCR circuits, my big VFD (11 KW) has a contactor that clunks a half second after power-on, so it uses a resistor and relay to short the resistor after the cap bank is charged.
2.5 mH is sure not going to help much with the inrush surge.
Jon
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wrote:

Thanks Jon. Even though I'm pretty good at wiring up and fixing my machines, both the mechanical and electronic parts, I still often need some hand holding and/or guidance. Help from folks like you is really appreciated. Eric
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From what I have read you DO NOT need a line reactor for short runs. Some writers disagree about what is considered short, but most say ten feet or less. Some users have reported no problems with slightly longer runs. I do use a shielded high flex cable between the VFD and the motor with the shield going to the same common ground as the VFD. I just connect to the ground screw on the VFD. I have not noticed any significant noise problems in my shop with multiple computers running and two CNC machines with VFDs running at the same time. I haven't even noticed any problems when welding when I forgot, but I typically do not weld while a CNC machine is running.
Where you need to derate is at the VFD itself. 1/3in 3out VFDs typically must be derated by about 30% when running on single phase. This isn't even an issue unless you will have peaks in that top 30% of rating. I am running a couple 800kw spindles on 1/3 750Kw VFDs without issue. I plan all cuts at .25hp or less anyway. I go for light fast cuts for most jobs. Usually in the .11hp or less range.
On my Hurco KMB1 I am running a 5HP Leland spindle motor with a 3.7Kw Mitsubishi VFD with no issues. I overloaded it once or twice and it just shut down. I have my SF calculator set at 3hp for that machine now, and have had no issues since. I would note that Hurco did not originally rate the machine at 5HP either. You do need to be aware of load in corners of pockets etc. Typically that peak it doesn't last long enough to be a problem. Only sustained cutting at max load, which I don't do anymore.
Spedestar makes a line of VFDs that are rated for full label load (peaks) with single phase input. I have debated on buying one for the Hurco, but I really don't need to push it that hard anyway. By going with lighter cuts and faster feeds I get better parts (in my opinion) anyway. Except for large bit drilliing in steel I rarely get calculated loads anywhere my self determined limit of 3HP anyway.
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I only do that on my high speed spindles. The Hurco is wired with stranded THHN in flex conduit, and then open inside the head.

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wrote:

The run from VFD to motor is short, the run from the VFD to the breaker panel is long, about 45 feet. All the wires in my shop run in either metal wire ways or metal flex conduit. I don't know if this makes any difference. The wires for powering the VFD are in the same conduit and wire way as the wires powering the Fadal and I don't know if this might be a problem either. I also am a little concerned about grounding. The VFD manual says it should have its own ground, to not share ground with anything else. For the larger machines in the shop each has a ground wire running from the machine to the load center ground bus bar. For some smaller machines, less than 3 HP, grounds are shared. So there is a ground wire running through the wire way with pigtails going to several machines. The circuit I want to run this VFD from has this shared ground. I could pull another ground wire but it's a real hassle to pull wire through the overhead flex conduit that the supplies power to the side of the shop the VFD will be on. Any thoughts on that? On your advice I bought a spindle/VFD package that is rated about twice as powerful as the heaviest cut I plan to make. So it looks like the derating business is taken care of. I program virtually all inside corner milling as arcs and use cutters with a smaller radius than the inside corner in order to reduce cutter load and chatter. Thanks, Eric
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Bob La Londe wrote:

I think you are talkign about a LOAD reactor in this case. It is to protect the motor windings from high voltage and rapid voltage swings from the VFD OUTPUT. The OP is asking about reactors on the INPUT to the VFD.
Jon
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    [ ... ]

    And if you have the cable (unshielded) already -- you can try with that for the run from VFD to motor and see whether there is any interference. If you see what looks like some, get a roll of aluminum foil, wrap it around the cable full length and ground it at the VFD end. If what you considered to be interference goes away, then it is time to spend the extra money for the shielded cable. Or route it through flexible conduit which does a pretty good job at shielding anyway, and protects the cable from abrasion.
    Good Luck,         DoN.
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