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The wiring diagram is the other issue which you said will need a little engineering help. Best Regards, Roger --Previous Message--
Thank you for your suggestions,& the Auto Starter Relay Sw Idea.
You asked what I was using to Charge the Capacitor?
I am using an Adapter Power Supply, Class 2 with 110 Volt input & 20 Volt DC at 1 amp.output to Charge the 2 Farad Capacitor & it will Spot Weld Sheet Metal.
: --Previous Message--
: I've built a Spot Welder using a 2 Farad Capacitor & using a
: Automotive
: DC Relay to Switch the Charge to the Electrodes & Spot Weld the Sheet
: Metal.
: After each Spot Weld the Relay contacts Fuse together & need to be
: Phyically Separated inorder to Do another Spot Weld.
: Can you suggest a Swtching Setup that will not Fuse the Contacts & a
: Wiring Setup to Turn off Power after each Weld, when the Contacts Don't
: Fuse Together.
: Now the Power has to be Shut off after the Weld is Made, the Work removed
: from the Electrodes, then the relay Contacts Separted, Setup the New Work
: to be Welded & then Turn On the Power to Charge the Capacitor, &
: Close the Switch to Weld.
: Thank You for Considering my inguire.
: What a Great Web Site you have.
: Sincerely,
: Roger Laghezza
: :
: Hello Roger,
: I assume you are using something similar to a starter solenoid/relay to do
: the switching of Ultracapacitors? Options for relay type switching would be
: making a custom high current relay that uses large diameter tungsten
: contacts - the high melting temperature of the tungsten should be a bit
: more difficult to weld. You will need to use a high pressure air cylinder
: in order to quickly develop the contact pressure necessary to prevent
: magnetic forces from trying to separate your contacts under load (which
: will overheat and weld them). Another alternative is a commercial high
: current relay, such as Ross Engineering GA, GB or GD series. These are
: specifically designed for high voltage capacitor discharge applications
: (much higher voltages than youre using). Unfortunately these are probably
: overkill, as well as being quite expensive - see the following URL to see
: what these look like:
: http://www.rossengineeringcorp.com/high_current_switches.htm
: A bank of high current SCR's or IGBT's (a type of high power transistor)
: might also work, but this option would also be fairly costly unless you
: were able to find some less expensive devices on the surplus market.
: Recently, some very high current SCRs and IGBTs have been appearing on
: eBay at fairly good prices.
: Commercial capacitor discharge welders avoid the problem of having to
: switch ultra high currents by using a higher voltage capacitor bank to
: drive a step down transformer (with a very heavy low voltage secondary
: winding) in order to generate a low voltage, very high current pulse. The
: capacitor bank is switched using either and SCR or (in earlier times or
: higher power systems) a special mercury vacuum tube switch called an
: ignitron. By switching a higher voltage, but lower current, pulse on the
: primary side of the transformer, the welder can develop an extremely high
: current low voltage pulse on the secondary side. This avoids the problem of
: trying to switch kilo-ampere currents at low voltages.
: You didn't mention how you were charging your capacitor bank. A small
: controller could be designed to properly sequence charging, welding, and
: unloading/reloading material, The controller could be as simple as some
: electromechanical relays, a microprocessor and interface hardware, or a
: small industrial programmable controller. Itll take a bit of engineering
: to pull it all together though.
: Good luck and best regards,
: -- Bert --
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