Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - petespaco

Pages: [1] 2 3 ... 7
1
Water Cooling Notes.  Here is the reply I gave to a guy recently relating to water cooling the work coil:
----------------------
I have a couple of questions if you don't mind.
where did you get your radiator from? I am using a 12x 5 cpu cooling radiator and it can't keep up with the required cooling.
----------------------------------------------------------------------------------------------------------------------------
I bought several radiators like the ones you see in my videos at a local online  auction house several years ago. They were all used ones. That style of radiator has one continuous tube that runs from input to output.  There’s no “tank” at the top, so it doesn’t really matter which end is the input. Although I have not tried this myself, I think the heater core from an automobile passenger heater would work well, using the fan/blower that comes with it.  The radiator on my 2500 watt unit holds a bit over 2 quarts of water, by the way.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------

There are several air pockets in the lines that may be the issue. Any suggestions on how to bleed the air out of the lines?
-----------------------------------------------------------------------------------------------------------------------
   Re: air pockets-  It may not be apparent on my setups but:
  Note that I have an expansion  chamber (later on, I used a plastic pop bottle, upside down with the bottom cut out) on both heaters.  I either take water from the outlet just below the expansion port or from the other end of the radiator.  Makes no difference, as long as the water level is higher than my piping to the workcoil , and as long as any bubbles that form are allowed out the expansion vent so they are  not trapped within the system. This expansion opening is also very important since the water expands significantly  when heated, and its also a sort of safety feature in case the water were to boil.
  One other REALLY important point: The pump MUST feed water into the BOTTOM of the coil.  This is the only way to be certain that the work coil is FILLED with water.  I once made the mistake of doing that backwards and produced many bubbles of steam before I realized what I had done.
------------------------------------------------------------------------------------------------------------------------------------------------------------

I have the same pump as you, but I am using 3/8 "clear tubing. I also can't get the pump to really circulate the water like it should be in my opinion.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Try to keep the pump and the radiator at about the same level.   Some guys put their water supply (usually a pail of some sort) on the floor, while the induction heater and pump are up on a bench.  The pressure output drops rapidly as the height increases, leading, of course, to lower flow.  Them if your radiator is very restrictive at all, flow gets even worse.

Link that will take you to most of my videos and webpages on the subject:
https://spaco.org/Blacksmithing/ZVSInductionHeater/1000WattZVSInductionHeaterNotes.htm

Pete Stanaitis
---------------


2
Electronic Circuits / Re: Induction heater
« on: February 07, 2020, 11:20:26 PM »
You might begin by setting some goals:

-What do you want to heat?
-How much power  will you need?

Basic assembled ckt boards  (without power supply, coolant pump, etc.):
150 watts? USD$10.00
1000 watts? USD$30.00
2500 watts? USD$50.00
7500 watts? USD$1000
and up, to many megaWatts.

The work coil is about the least complex component of the whole project.  Also, I wouldn't  a solid coil.  You need one that can be water cooled.

IGBT's?   I just read that they work best below about 20 kiloHertz.  If that is true, you may not find them a good choice for induction heating in the lower ranges above.  I hope others will comment on this point.

Start by googling "induction heating" or something like that and spend some time learning.

Pete Stanaitis
---------------

3
Electronic Circuits / Re: Prototyp construction techniques
« on: February 06, 2020, 10:43:36 PM »
@Da_Stier:

I don't think there ARE any links in that Word document.  Did you actually get 404's someplace?
I did notice that one time it took a while for the images to load, though.
If you did find an actual link, I'd appreciate it if you would reply here with the info.
I did notice that some of my spelling errors  and poor grammar (shame on me) have red or blue underlines, but they are NOT links.

Has anybody else had an issue?

Pete Stanaitis
---------------

4
Electronic Circuits / Re: Prototyp construction techniques
« on: February 06, 2020, 09:02:34 PM »
Wow!, Mads, you do some really nice looking complex stuff.

Since we are on the subject of prototyping, here's the link to document I put together 5 or 6 years ago about various methods of assembling electronic stuff:
https://spaco.org/Computing/Wiring up electronic components DetailWPix2.doc

Is there anybody on this forum old enough to know what a "Fahnestock Clip" is?

Pete Stanaitis

5
Lately some Russian hobby size induction heating videos have been coming up on my Youtube recommended list.  I don't understand the language, but I can get a pretty good idea of what is going on from almost all of them.
  Anyway, here's one where the guy simply couples the output from an induction HOB (British for "Hotplate Or Burner) to some copper coils and then parallels the output part of the coil structure to some capacitors.  So, as far as I can tell, without modifying the HOB in any way, he has a high frequency driver.  Maybe not great at power transfer, but I thought it was an interesting Hack:
/>
Pete Stanaitis
---------------

6
Thank you for your kind words, Mads.
   Nice demo of the little 150 watt unit.
Several members of our blacksmith club enjoy making things from horseshoe nails. This unit is just right for that.
If you power it from a 12 volt car battery (or appropriate rechargeable battery pack), you have a very portable heat source.

Salt spoons and finger rings are but two examples.
Works well for making tiny swords from double headed (duplex) nails, too.

Pete Stanaitis
---------------

7
Electronic Circuits / Re: 10 kVA Kjellberg Plasma Cutter CUTi 31 Teardown
« on: January 05, 2020, 01:10:11 AM »
I agree that many of our shop tools (as well as their owners) suck in a lot of bad dust.  We should all probably have  good exhaust systems, but yet, I don't.  I have much better dust collection in my wood shop than I do in my metal shop.
Not so worried about the old stick welder and big mig welder because they don't have any electronics to speak of.  But I think there's a big opportunity for the makers of newer inverter based equipment to do a better job of filtering.
I have blown up enough Mosfets over the last few years with my induction heaters to understand how some conductivity between gate and drain/source could lead to disaster.
  Several months ago, when we were holding a blacksmith meeting at a local chain Welding supply company, I noticed a large pile of trade-in welding power  supplies that was being scrapped.  Maybe for those same (conductive dirt) reasons?

Pete Stanaitis
---------------

8
A little more  information for people who want to make specialized work coils:
I just updated my work coil spreadsheet.
It is here:
http://www.spaco.org/Blacksmithing/ZVSInductionHeater/Work%20Coil%20Data.xlsx

I added an area down toward the bottom that I call "guessitmates.  This is where I enter the data that I do have, usually  physical coil dimensions and measured (not necessarily actual) inductance.    As I have said many times before, if the coil's inductance is higher than about 1.0 microhenry, then the ZVS driver will run at a low enough frequency to avoid overheating of a properly cooled system.


Pete Stanaitis
---------------

9
Cobalt in your future?
Many readers of this thread have asked about methods to melt copper faster.
  We typically use ceramic insulated graphite crucibles, which work pretty well, but
1. don't push the 2500 ZVS induction heaters to their power limit, even when on 48 volts
2. their graphite is comsumed during the process, which limits one crucible to about 10 "heats" before it gets so thin that it is dangerous to use.

So I was thinking that a steel crucible might melt copper a lot faster than do the graphite crucibles due to their magnetic/hysterisis characteristics.  Problem is that they lose their rapid heating abilities well below the melting point of copper.

I just realized that Cobalt has a curie point of 2067 degrees F, well above the curie point of iron  (1418 F, or thereabouts).  I wonder if there's a cobalt crucible in my future, but I won't lose any sleep thinking about it, since that metal costs about USD$75.00 per pound.   And, there probably aren't a lot of Cobalt crucibles on sale at Ebay.

10
Some interesting recent comments, but still don't have a good handle on best frequency for melting copper in a graphite crucible.
   It certainly isn't all that simple, is it?

I have found a few "Induction Heating Calculators" around on the internet.  I think they probably do a fairly good job of estimating a few variables when it comes to iron and lower alloys of steel, but they seem to miss the target when getting into non-ferrous metals.
  For instance, here's one of the "calculators":
https://www.plustherm.com/power-calculation.html

It took me some time to figure out how it works.  (Note that you put in the whole number for the "Inductor Efficiency", not the percent as a decimal.  That is- if your material is  Aluminum, enter "40" not "0.40").

In the "Results" area, I am very dissapointed that it usually outputs an extremely low frequency in the "Minimum required frequncy" box.  Why doesn't it know what frequency it actually used for that particular calculation?
  And--- I am pretty certain that the results from their "minimum" frequecny and the ideal frequency would produce differing readings.

At first, I left the "Working Frequency" blank, so the calculator could choose, but even when I did enter a number, it didn't seem to help much.

After fooling around with the thing for a while, I realized that we aren't actually melting copper anyway with these 1800 watt to 2500 watt ZVS induction heaters, we are heating a graphite crucible!  Well, there's no graphite in the Material choices box, so now what?  I made a few guesses in the Inductor Efficiency box, estimating the graphite to be somewhere between "60" and "85", but no conclusive results.

It seems that some of the parameters in the  "Details" area not closely related to the input parameters at all.

What do you guys think?

Pete Stanaitis
---------------

11
Effect of frequency on melting copper???

Recently, a guy asked me how to change his ZVS induction heater's frequency so he could keep the current up as the copper melted in a graphite crucible.  He has observed that the current drops at the moment the copper melts.  I think many of us have seen that effect.  My guess is that the molten copper shorts out the  carbide crucible or somehow reduces eddy currents in the graphite.  He must think that changing the frequency will get the current back up to where it was before the copper melted.  I don't think that's a viable option with these ZVS heaters.

Anyway:
A confession:
   I lack a practical understanding of the exact degree to which frequency affects the heating of copper and brass.
  After reading everything I can find on the internet, it seems generally accepted that higher frequencies are better for non-ferrous metals.
  That's nice, but it also appears to me that the people who are heating copper parts commercially almost always use induction heaters that have a lot more power than do the 1000 watt to about 2500 watt heaters that are the subject of this thread.
  Then there's the (apparently) very popular "15KW" induction heater of which this is one example:
(search this on Ebay)-
"220V 15KW 30-100 KHz High Frequency Induction Heater Furnace"
(Be warned, however, that this heater really only puts out about 7.5KW AND, you need a pretty good water cooler to use it!).

There are plenty of videos where the operator melts copper or at least heats some parts up for soldering or brazing.
  But we never, as far as I know, get to see what frequency the thing is running at when this takes place.


All that said, if appears to me that you need more than about 5KW to melt a kilogram of copper or more in a graphite crucible anywhere in the range of about 25 kiloHertz to about 100 kiloHertz.  Once you have a lot of power available, then you can start messing around with frequency, if your circuitry allows it.

Conclusion:
I don't have a good answer for that guy.  We can change the frequency of these ZVS heaters by changing the L (size and shape of the work coil) and C (adding or subtracting capacitors) in the circuit, but that's not what he thinks he  wants.  I told him that insulation and MORE insulation is his friend.

Your comments, please.


12
A positive thought for you guys who  are using multiple 12 volt power supplies:
 People are often asking me how to control the power that the  work coil transfers to the work of the ZVS heaters that I use....
If you are using a 48 volt power supply, as I do, then the two main ways to accomplish that is to either:
1. move the work closer to or farther away from the work coil until the current is at the level needed.
or-
2. Change work coil design to match the needs.
But, in many cases, the operator needs to adjust the power one direction or another as the work heats up.
An example of this would be when heating a piece of iron or steel-   Initially, if the work piece must be inserted into the work coil before the power is turned on, the current sucked up by the workpiece may exceed safe limits for the circuit, but once the part reaches the curie point, you need MORE POWER.
In this case, if you were to arrange your power supply switching so that you could start out with, let's say 24 volts and then switch to 36 volts or to 48 volts as needed, you'd have at least 3 power levels available.

Just a thought.   I am not saying that the switches would be simple, but it certainly isn't impossible.
And------- note that I did NOT suggest starting out with 12 volts.
I hope you all know why by now.

Pete Stanaitis
---------------

13
Just a Mosfet thought, relating to the recent posts about IGBT/Mosfet gate drive:
  I can't see ANY reason not to turn on these devices ASAP.  By that I mean that these devices, as far as I know, are SWITCHES and are NOT meant to be run in linear mode.  A main reason that they can handle such high currents is their low RDS(on).  So, if they are NOT fully on, very high amounts of power can easily be produced.
  Don't "baby" the gate.  Get it up to "full on' ASAP.  As previously mentioned, if the power supply can't hack it, get a better one. 

Pete Stanaitis
---------------

14
Quote
However, you need more current head room the lower voltage you are operating at. A 12VDC supplied homemade Royer with IRFP250N would get unstable below 10VDC, so it is far more prone to failure than a 36VDC suppplied Royer circuit from China.

Yes, I'd say that is exactly correct.

About 2/3 of the way down this page you can see 4 scope traces of gates turning on with differing input voltages from 12 to 48.
https://spaco.org/Blacksmithing/ZVSInductionHeater/1000WattZVSInductionHeaterNotes.htm

As far as the "core saturation" thing goes:
  I am no expert on transformers, but I have rewound a couple of microwave oven transformers and I have taken some data on their "regulation" or whatever you want to call it, under varying current  draws.
/>  In this video, I show two charts that demonstrate  transformer output voltage reduction as current increases.

Pete Stanaitis
--------------

15
Quote
When it comes to switching on and off

What will you be switching on and off?
What supply voltage?
what frequency?
what current?

Pete Stanaitis
---------------

16
Quote
For a PI control, I would not use a mechanical relay, but a solid state, a mechanical DC relay at this current would get worn out too fast.

What kind of insulation material did you use in that video?
------------------------------------------------------------------------------
I agree with using a solid state relay.  I have been looking at this one:
https://www.amazon.com/100A-Solid-State-Relay-SSR/dp/B00KO46YCU
but it is only rated for 32 volts.
I think they get pretty expensive when you get to 50 volts or so.

Insulation:
I use 8 pound density  one inch thick Kaowool that is rated for about 2300 degrees F service.
It is the material the we use in propane gas forges.  In that test I was simply tearing up small bits of it and stuffing them in beside the work.
If you search "kaowool" on ebay, you will find many sizes and thicknesses.
I see today that it is available in thicknesses down to about 1/4 of an inch.  I wish I had realized that when I bought another kind of "ceramic" insulation a few months ago. 
It was this stuff:
https://www.ebay.com/itm/INSWOOL-2300-PAPER-Flexible-Refractory-Paper-1-8-x-50-partial-rolls-also/131815404577?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
  I bought it because it is thin.  It insulates quite well, but this material has some sort of chemical binder that burns away leaving the ceramic material behind.  With the binder gone, the insulation has very little strength left and it falls apart if mishandled.

Pete Stanaitis
---------------


17
Hello Mads.
  You did a very nice job of packaging your 1800 Watt ZVS induction heater.
I like your idea of the big DC relay.  That should make it easy to add PID temperature control some day.

Several other induction heater experimenters have complained about ZVS heaters, saying that they do NOT start up reliably.  I have never had this problem.  Why do you think they say this?

I, too have been trying to get steel hotter than the curie point.  The only time it has worked for me is when I insulate between the work and the inside of the work coil, and cover the work, too:

You can see the high temperature part of this video at about 20 minutes in.

Pete Stanaitis
---------------

18
The making of induction heater work coils the way I do it and why-
  That's the focus of my newest ZVS 1000 to 2500 watt  12 to 48 volt induction heater video.
It is here:
/>
I'd be glad to entertain any comments, questions or criticisms.
  As they say somewhere:  "There's more than one way to skin a cat".
It's just the anyone who doesn't do it my way is wrong. <G>

Pete Stanaitis
---------------

19
Just to belabor the point about scoping the coil voltage:
I now remember that I was using my little DSO-112 battery powered scope early on when I had been taking readings.

Pete Stanaitis
---------------

20
Quote
Has there been any testing of the limits in terms of coil frequency with 48V 1,000W or 2,500W units?

Yes.
I have not found a lower frequency  limit yet, but lower seems to be better for the Mosfets.  Things still work well down to about 26 kHz.
It's the upper limit that I have spent most of my tine evaluating.

See my data and my opinions here:
https://spaco.org/Blacksmithing/ZVSInductionHeater/WorkCoilsForZVSInductionHeater.htm
--And click on the "Work coil, Observed" spreadsheet.

Pete Stanaitis
---------------


Pages: [1] 2 3 ... 7

* Recent Topics and Posts

post Re: Unusually long-lived electrolytic capacitor
[Electronic Circuits]
ritaismyconscience
Today at 06:08:05 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
Today at 05:55:55 AM
post Re: Unusually long-lived electrolytic capacitor
[Electronic Circuits]
T3sl4co1l
Today at 05:51:48 AM
post Unusually long-lived electrolytic capacitor
[Electronic Circuits]
MRMILSTAR
Today at 05:43:34 AM
post Re: Tesla coil Toroid Aluminium tape benefit
[Spark Gap Tesla Coils (SGTC)]
Jun
February 25, 2020, 01:26:37 PM
post Re: Tesla coil Toroid Aluminium tape benefit
[Spark Gap Tesla Coils (SGTC)]
dj.cosmo.esq
February 25, 2020, 01:05:01 PM
post Re: Tesla coil Toroid Aluminium tape benefit
[Spark Gap Tesla Coils (SGTC)]
Jun
February 25, 2020, 12:35:06 PM
post Re: FPS4000
[High Speed Filming]
Mads Barnkob
February 25, 2020, 11:29:58 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
February 25, 2020, 08:28:28 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 25, 2020, 06:27:40 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 25, 2020, 06:20:04 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 25, 2020, 04:23:50 AM
post Re: Tesla coil Toroid Aluminium tape benefit
[Spark Gap Tesla Coils (SGTC)]
Mads Barnkob
February 24, 2020, 02:53:13 PM
post Tesla coil Toroid Aluminium tape benefit
[Spark Gap Tesla Coils (SGTC)]
Jun
February 24, 2020, 02:38:29 PM
post Re: NST
[Spark Gap Tesla Coils (SGTC)]
Jun
February 24, 2020, 02:30:28 PM
post FPS4000
[High Speed Filming]
Hoser415
February 24, 2020, 02:21:50 PM
post Re: HP T620 thin to plus conversion....
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Mads Barnkob
February 24, 2020, 09:09:33 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 24, 2020, 07:08:30 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 24, 2020, 04:37:33 AM
post Re: DIY 250W LED Flood Light for High Speed Filming
[Light, Lasers and Optics]
Mads Barnkob
February 23, 2020, 09:04:34 PM
post HP T620 thin to plus conversion....
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
spacecabbie
February 23, 2020, 02:03:15 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 23, 2020, 05:43:17 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
klugesmith
February 23, 2020, 04:07:51 AM
post Finding accelerometer location inside a phone
[Smart Phones]
haversin
February 22, 2020, 07:23:28 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
dj.cosmo.esq
February 22, 2020, 07:41:18 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 22, 2020, 06:49:22 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 22, 2020, 03:39:10 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
Quentief
February 22, 2020, 02:32:55 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
klugesmith
February 22, 2020, 02:10:34 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
Quentief
February 22, 2020, 01:27:41 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
February 21, 2020, 08:00:10 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
February 21, 2020, 02:44:44 PM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
klugesmith
February 21, 2020, 07:21:13 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 21, 2020, 06:11:32 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 21, 2020, 04:42:34 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
davekni
February 21, 2020, 04:37:53 AM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
Twospoons
February 21, 2020, 04:28:33 AM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
klugesmith
February 21, 2020, 04:21:31 AM
post GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 21, 2020, 02:41:03 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
Quentief
February 21, 2020, 12:28:20 AM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
Twospoons
February 20, 2020, 09:45:21 PM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
klugesmith
February 20, 2020, 07:28:01 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Uspring
February 20, 2020, 02:06:26 PM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
shrad
February 20, 2020, 10:38:01 AM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
davekni
February 20, 2020, 05:14:43 AM
post Re: Is this flyback OK for my Plasma ball ?
[Transformer (Ferrite Core)]
davekni
February 20, 2020, 05:04:50 AM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
klugesmith
February 20, 2020, 04:47:41 AM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Peregrine
February 19, 2020, 07:29:23 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Peregrine
February 19, 2020, 06:47:55 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Peregrine
February 19, 2020, 06:45:23 PM

SimplePortal 2.3.6 © 2008-2014, SimplePortal