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Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Marx generators are high voltage impulse generators typically single-shot. Cockroft-Walton multipliers are used to generate high voltages, but at very low currents.
Registered Member #32
Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549
Although CWs have been made to extremely high voltages, a marx generator can be cheaper as the voltage goes up, especially for amateurs. A higher voltage marx essentially needs wider gaps and thicker capacitor dielectric. A CW in practice will probably need diodes with higher voltage ratings - hard to get for many people.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
Let's say I wanted to build a Marx Generator. I set up each stage of resistor/cap/SG. How would I "tune" it to fire just right? Would I adjust the spark gap of stage one until it just fires near full cap voltage and then adjust the next spark gap to fire just below the peak charging of cap2 + the discharge of cap1, etc?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
There are two mechanisms that make the other gaps fire once one gap has fired. Stray capacitance to ground raises the voltage on gaps adjacent to a arcing gap, and UV from the first arc ionises the air in the other gaps IF they are all in a straight line and can "see" each other, regardless of which gap goes first.
If you are not too bothered about controlling the firing time exactly, make all the gaps the same size, and wait for the first one to strike as you charge. In practice, the voltage on the upper gaps will be less than that of the lower gaps due to the charging RC time constants, and corona losses if the voltage is high enough, so it is still likely to break down bottom gap first.
If you do want to charge, wait, then fire, make the first gap a triggered gap.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
There is another important difference between CW and Marx for the amateur who wants to get the biggest bang for the buck: With a CW you have two columns of capacitors, so the maximum peak voltage attainable is only half of the total your capacitors can stand. I.e. for a given amount of caps, a Marx gives you twice the voltage. In addition to that, you have much less corona problems, since you only reach the peak voltage for a few 100ns. High voltage resistors and diodes are about equally hard to get, so thats not really a point IMO.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Rectfied iggie may be a try for MG but it gives out very low current and it would take centuries to charge and fire marx (or corona will eat power faster and it wouldnt fire at all). Usually rectified flybacks, NST's and OBT's are used.
For CW multiplier high frequency supply is used (flybacks at most) so we can use small caps and it gives continuous HV output.
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Marx vs. WC multiplier
