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rlf
Trad climber
Josh, CA
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May 28, 2012 - 09:15pm PT
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Here's my next puzzle. Deciding exactly how much potential for issues over time with the motors the graph below could cause.
Notice the phase differential between the voltage (red) and the current (blue). Not too mention the harmonics...
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TGT
Social climber
So Cal
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May 28, 2012 - 09:26pm PT
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Looks like you may have some wicked third order harmonics going there.
Did you oversize the neutral?
I'm sure that if it's a used transformer it isn't K rated.
See if you can find a clamp on amp meter that does both peak and true RMS. you can get a handle on the practical effects of the harmonics from that. No need for anything more sophisticated.
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rlf
Trad climber
Josh, CA
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May 28, 2012 - 09:31pm PT
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Thanks Wendell, I may be giving you call. I have the tools. The harmonics appear to be peaking at around 480Hz (roughly 8 times the fundamental).
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TGT
Social climber
So Cal
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May 28, 2012 - 09:52pm PT
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Even harmonics are probably an artifact of the phase converter then. They cancel in the neutral so no issue there. Not sure what it's going to do to the spindle motors though. The axis drive motors are probably DC steppers so there should be no issue with them.
watch the temps on the spindle motors if you have a way to do that.
You got some weird sh#t goin on there.
but, that's what happens when you are stuck with using phase converters.
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rlf
Trad climber
Josh, CA
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May 28, 2012 - 10:04pm PT
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Thanks for the confirmation. That's what I've been seeing. Yes, the Axis motors are indeed DC steppers. It's the $25K spindle motor that has me very worried.
I was asked to design a system. I did. This is the hardware I ended up with (not my choice).
I have an IR therm I can use to check the heat on the spindle. If that sucker burns out, it's a real problem. A real expensive problem.
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TGT
Social climber
So Cal
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May 28, 2012 - 10:18pm PT
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Is the spindle motor on a VFD?
that may save your ass.
I'd check waveforms right at the spindle motor all the way thru its operating range.
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rlf
Trad climber
Josh, CA
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May 28, 2012 - 10:20pm PT
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That's a good question. I should have some more data/answers by weeks end.
Thanks!
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TGT
Social climber
So Cal
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May 28, 2012 - 10:26pm PT
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Another thought.
If you have a small transformer you could try putting it on line and checking the waveforms on the output side. Not sure that will work, but it would be worth a try.
If that cleans it up going to an isolating transformer might be the ticket, especially if you can get your hands on an electrolytically shielded K rated one.
Another thought,
It sounds like you have mostly a switching power supply load and little true there phase load.
one thing I've done with capacitive three phase converters is put an idler motor on the load side.
Just an old 3600 rpm motor, maybe 1-5 hp just idling along. It functions sort of as a synchronous alternator and cleans things up a lot.
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rlf
Trad climber
Josh, CA
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May 28, 2012 - 11:20pm PT
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Thanks Wendell.
Your insight tells me I'm on the right page.
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Scole
Trad climber
San Diego
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sibylle
Trad climber
On the road again!
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Remodeling my mother's bathroom in the Bay Area -
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sibylle
Trad climber
On the road again!
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I'm working on enlarging my mom's bath.
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guido
Trad climber
Santa Cruz/New Zealand/South Pacific
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Mtnmun
Trad climber
Top of the Mountain Mun
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The perfect way to ruin a beautiful piece of wood, put ski boots on it.
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1 Rusty Piton
Trad climber
Jamestown, Rhode Island
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Jun 15, 2012 - 11:25am PT
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ydpl8s
Trad climber
Santa Monica, California
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Jun 15, 2012 - 11:46am PT
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I think that ski boot coffee table belongs on the "Every Picture Tells a Story" thread. I love old ski equipment and I love beautiful wood, but that???arrgghh!! not good.
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Brandon-
climber
The Granite State.
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Jun 22, 2012 - 02:05pm PT
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Nice panel.
I've been busy. The project;
Full gut and remodel of existing. Addition doubling the size.
The view;
Mt Monadnock.
Yeah, my partner is a woman. She kicks ass and it's great to see women in the trades.
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Reilly
Mountain climber
The Other Monrovia- CA
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Jun 28, 2012 - 11:26am PT
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Dood! You need a better flash (or four) but we get the idea.
When is too much not enough? Sick! :-)
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Robb
Social climber
The other side of life
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Jun 28, 2012 - 11:47am PT
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Brandon,
Go fix that roof shingle man.
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Brandon-
climber
The Granite State.
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Jun 28, 2012 - 11:48am PT
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Robb, way ahead of you man.
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