: Hello ,
: I have been reading your site with great
: enthusiasm and was wondering if I may
: prevail upon all of your extensive
: 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
: 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
: 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
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 firstname.lastname@example.org