I have been reading your site with great enthusiasm and was wondering if I may prevail upon all of your extensive knowledge?
While I am a personal enthusiast of Nikola Tesla, and love his work, this message is not necessary about Tesla Coils, but may borrow some of the knowledge base.
We are currently building/repair our custom magnetizer, (for which there is no support) and I am running up against some problems with high energy switching.
Normally we would use a High current SCR's and a Free Wheeling Diode for blocking.
So far, my attempts have failed in burned out units.
We have a capacitor bank that has 47,000 uf @ up to 380 volts for the impulse into the magnetizing coil.
That is the maximum we will be switching. Perhaps less to do our work.
I own a ultra-high end Audio Speaker company, and the magnets we need to magnetize are pretty healthy units. They run in the 1.2 to 1.5 T range in the Voice Coil gap. The magnets are relatively small and are built around an Alnico V-7 slug that weighs 2.2 lbs. The magnetic pot structure is solid soft iron and weighs 10.5 lbs with the magnet inside.
It has a dimension of the following... 4.25" diameter x 2.750" height.
Our magnetizing coil is a free standing air coil with a 4.5" I.D. x 3" height x 6" O.D. Wound on Phenolic core with #10 ga. copper wire and 600 turns. Each layer is insulated via .010" fish paper and the whole coil is impregnated with Xformer varnish and baked. Top and bottom of the coil have 1/8" phenolic rings to retain the coil windings. Resistance is .25Ohms.
Can you recommend a value for the Blocking diode...i.e. PIV and Current?
Can you recommend a value for the SCR PIV and Current. We are using SCR Puck and Diode Puck style, though stud mount would be OK.
Duty cycle for our machine is very low. Perhaps 1 sot every half hour.
I am open to using a Trigatron for switching and a Blocking diode if you think that would be useful.
I can send pics if you like.
Any thoughts?
Kind regards, Dale Harder HHR Exotic Speakers 440-888-2163 up to midnight EST 24/7 www.hhr-exoticspeakers.com
--Previous Message-- : Hello , : : I have been reading your site with great : enthusiasm and was wondering if I may : prevail upon all of your extensive : knowledge? : : While I am a personal enthusiast of Nikola : Tesla, and love his work, this message is : not necessary about Tesla Coils, but may : borrow some of the knowledge base. : : We are currently building/repair our custom : magnetizer, (for which there is no support) : and I am running up against some problems : with high energy switching. : : Normally we would use a High current SCR's : and a Free Wheeling Diode for blocking. : : So far, my attempts have failed in burned : out units. : : We have a capacitor bank that has 47,000 uf : @ up to 380 volts for the impulse into the : magnetizing coil. : : That is the maximum we will be switching. : Perhaps less to do our work. : : I own a ultra-high end Audio Speaker : company, and the magnets we need to : magnetize are pretty healthy units. They : run in the 1.2 to 1.5 T range in the Voice : Coil gap. The magnets are relatively small : and are built around an Alnico V-7 slug that : weighs 2.2 lbs. The magnetic pot structure : is solid soft iron and weighs 10.5 lbs with : the magnet inside. : : It has a dimension of the following... : 4.25" diameter x 2.750" height. : : Our magnetizing coil is a free standing air : coil with a 4.5" I.D. x 3" height : x 6" O.D. Wound on Phenolic core with : #10 ga. copper wire and 600 turns. Each : layer is insulated via .010" fish paper : and the whole coil is impregnated with : Xformer varnish and baked. Top and bottom : of the coil have 1/8" phenolic rings to : retain the coil windings. Resistance is : .25Ohms. : : Can you recommend a value for the Blocking : diode...i.e. PIV and Current? : : Can you recommend a value for the SCR PIV : and Current. We are using SCR Puck and : Diode Puck style, though stud mount would be : OK. : : Duty cycle for our machine is very low. : Perhaps 1 sot every half hour. : : I am open to using a Trigatron for switching : and a Blocking diode if you think that would : be useful. : : I can send pics if you like. : : Any thoughts? : : Kind regards, : Dale Harder : HHR Exotic Speakers : 440-888-2163 up to midnight EST 24/7 : www.hhr-exoticspeakers.com :
Hello Dale,
Sorry for the very long delay in responding. I just discovered a backlog of unapproved messages on this message board.
Because of the low voltage capacitor bank, a trigatron will not work. A magnetizer requires a unipolar waveform to the work coil since any ringing will weaken or demagnetize the magnet. In addition, electrolytic capacitors cannot withstand voltage reversals. A suitably rated SCR or IGBT should work as the switch. And many IGBT's contain internal freewheeling diodes, simplifying the design.
If you still need assistance, please contact me at bert@capturedlightning.com
