If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Hi. Not sure -adding- turns will help. It will reduce the volts per turn (so -less- flux density everywhere), and doubly reduce the no-load magnetizing current.
Suggestion: if you add 100 turns, keep both ends of the new winding accessible, and not permanently connected to the original 600 turns. Then by changing the external series connection, you can switch between 500, 600, and 700 effective turns. When new winding is connected "backwards" there will be a place with much more than usual voltage between layers. So you might want to cover old winding with heat-resistant tape or paper before starting the new winding.
The heating watts depend on 2 things: the induced voltage in 1 turn around the crossbar, and the electrical resistance in that direction of the part being heated. If you want to try a load that would draw more mains current and heat faster than the bearing, how about a thick brass/bronze pipe fitting, or thick aluminum part with a hole, or a short-circuited bearing-sized winding of any gauge copper wire or tubing? (Metals that conduct electricity many times better than steel).
[edit] oops, forgot about skin effect. In strongly magnetic materials like carbon steel, the induced AC current only flows near the surface of the bearing race. That increases the effective resistance and reduces the heating power. Now your observed heating rate is not far out of line with the model. To get 2 kW, I bet the commercial heater must be tested with a much bigger bearing and/or one made of highly conductive, not-very-magnetic metal.
Registered Member #1838
Joined: Tue Dec 02 2008, 06:01PM
Location:
Posts: 38
I added the extra wire yesterday, to make the total turns 724, it did reduce the no-load current by about 30%, but the time to heat the bearing increased by approximately one minute. I dropped 64 turns (3 turns/volt), but once again the only significant change was the no-load current. Heating time was about the same. So I decided to stick with the original 600 turns, because it gave me the best heating time and then I don’t need to change the enclosure to fit the coil. Today I added a secondary of 40+40 turns for the display and finalized the project.
Concerning the heating time. I never managed to heat that bearing in 2min again, all my runs ended up 2m40s. Now with the enclosure it takes 3m40s from 24-100C (I did make the part that encloses the uprights from non conducting material, fibreglass) but it seems just the presense of the metal box is enough to have that big an effect.
Thanks to all who help with the project, special thanks to Rich
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
Don't enclose the thing in a metal box! Anything conductive that completely surrounds the core limbs will be heated by induction and ruin overall efficiency, ...and anything magnetic that goes across between the core limbs will shunt magnetic flux away from the crossbar where you want it to heat your workpiece.
Registered Member #1838
Joined: Tue Dec 02 2008, 06:01PM
Location:
Posts: 38
The transformer is rather heavy for a plastic box and Im willing toe sacrifice a bit of performance for a neat enclosure. As I mentioned the top part of the enclosure is almost completely of 2mm thick fibreglass, so there can’t be significant circulating currant, the nearby metal will act as a shunt to some extent, but that I recon is not necessarily a bad ting. At this stage I must add that I discovered that the ambient temperature, have a huge influence on the heating times, I thought the influence would be neglect able. Heating times (24-100C) seems to be lower in recent days, closer to 2m40s. The nearest metal parts of the enclosure heat less than 5C during that time. Of course that again depends on the ambient temperature. I did not record the ambient temperatures when it did previous experiments, so its impossible to make a really scientific analysis of the performance change during the development. At this stage Im satisfied with the results. A project that I thought would be straightforward ended up teaching me quite a bit. A mechanic friend of mine assures me that this is a really handy tool to have. I would love to see other people build some bearing heaters also, maybe then we can compare results.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
2KW Bearing Heater
