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
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