I purchased a couple of large travelling wave tube amplifiers in an auction. I phoned the US company to ask about schematics and a manual ... "can we have the serial numbers please?" ... "sure ... " "great and what date did you sign the ITAR agreement?" <click brrrrr...>
On Mon, 18 Mar 2024 at 17:45, gene heskett <ghesk...@shentel.net> wrote: > On 3/18/24 11:28, Todd Zuercher via Emc-users wrote: > > Gene, > > > Well 2 things I've observed since posting that, Todd. the pix is > identical for a 3 kilohertz version on amazon for about the same price, > once adjusted to us dollars . So I'm wondering if aliexpress added an > extra 0, they rarely know what they are selling anyway. > > And since it showed up on amazon too, I'm wondering if the ITAR rules > have been relaxed. > > Here is the highest HP rated amazon offering. 15kw 20hp for about $1200: > < > https://www.amazon.com/Mollom-220V-15KW-20HP-Frequency/dp/B0CQBZ4FZN/ref=sr_1_52?crid=30GVV1U3R7JUA&dib=eyJ2IjoiMSJ9.5mKofR2CvOgdLO3tCtLjmKysBbvC8T8oTt4SNyV7-PqBQ6UsvOrsvyppX7rBUpjT2IZZ2mAWKRkL0H1nJj5MGcPBTDsP2EbqZePAsB09iFXxVTemY7Dr4c-fOZHZLdaaBQulJLMrOYJl5bQBZyyubX0LkNc-DuFlyrVam8hlnFXUx5O0mASax2WBIToQk1TnTgzTo9aSvbn0kcp1wxgKUbqJsSefz-wM0iZmaooVN5zTcqmgr8SzJWLCsHsviwy3aYCLB0dDN-JFW7Rw6Cp1GUTSqURhr6UCPywhkuSnYI0.1sKFN_5H6kH9Ju3mlK1mAlKX2LaJ6eM0Et-7LWB83CI&dib_tag=se&keywords=high+speed+high+horsepower+vfd&qid=1710778937&sprefix=high+speed+high+horsepower+vfd%2Caps%2C82&sr=8-52&ufe=app_do%3Aamzn1.fos.765d4786-5719-48b9-b588-eab9385652d5 > > > > I'd think that could run your 4 pole motor at 800hz just fine. UNK and > unstated in the adv is the control range so I would scale the 3k range > so max from the controller would only get you the rated speed at the > motor. But I don't have to tell you that, you've been dealing with those > sorts of problems with that machine for long enough this ought to be the > best answer. Sometimes this is self limiting, higher frequencys run > into the motors inductance, coil current falls and the motor actually > slows down, my Sheldons max usable speed while running a 70 yo motor > that never saw a vfd until me is about 200 hz as the coil current is > under an amp at 200 hz. 3.7 amps at 60 hz. OTOH it can run it at 5hz > long enough to finish the job and still lay my hand on that motor w/o > discomfort from the heat. > > As for needing a new one, the usual failure is going to be the line > stage filter caps which often will have a note in the docs someplace to > the effect that they should be replaced at 5 year intervals, however the > smaller ones that don't have braking resistors are actually 4 quadrant > controllers, meaning a quick reversal will overvolt those filters for a > few milliseconds as they do the reversal, they suck that power out of > the motor stopping it, storing it as overvoltage in those filters, then > as soon as the new direction is applied use that stored energy to spin > the motor back up in the other direction, so the overvoltage is not > present long enough to damage them, but actually contributes to > maintaining the "forming" of those caps so they live longer. The 1.5 hp > rated el-cheapo clone running the 1 hp in my Sheldon lathe is now around > 9 years old and can still reverse that motor and its 40lb 8" 4 jaw chuck > in under 1/3 second at 100 revs. Overshoot at 100 revs is .24 turns from > 100 rpm to stopped. And the shop lights don't blink. Its all in the .hal > file if interested. No circuit breakers in any danger of tripping as all > the excitement is in the vfd and doesn't involve the wall power. Just > give me a yip. > > These aren't toy's, they can kill, so give them the respect such killers > deserve. But I don't have to tell YOU that. > > Take care & stay well Todd. > > > In all honesty I wouldn't mind knowing more about your VFD source you > say you want black listed. I'm so sick of trying to track down high speed > VFDs that I'm almost tempted to pay the machine manufacturer's ridiculous > 3X normal retail list price markup the next time we need a new one. We > occasionally have needed a replacement VFD capable of running about a 15kw > 4pole router spindle at up to 24krpm (that is 800hz output, most drives > seem to max out at or are limited to 500-600hz output.) The last time we > tried to order a new drive with these specs it was put on back order for > more than 1 year before we canceled the order. (We canceled after the > delivery date had been pushed back 3 months for the 5th time.) Then we > bought a used one off of ebay. (Tracking down a used drive on ebay with > documented proof of the correct high speed firmware, when the sellers have > no clue, is also another annoying trick to perform.) > > That is what we get for doing unusual things Todd, Goes with the > territory. The trick is getting the info needed to make an informed > decision from someone who has NDI what those numbers represent. They > simply don't speak the language. And it can be very frustrating. > > > > Todd Zuercher > > P. Graham Dunn Inc. > > 630 Henry Street > > Dalton, Ohio 44618 > > Phone: (330)828-2105ext. 2031 > > Cheers, Gene Heskett, CET. > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
