Ignitron - Citizendia

(1) Anode, (2) Cathode, (3) Ignitor, (4) Mercury, (5) Ceramic insulators, (6) Cooling fluid

An ignitron is a type of controlled rectifier dating from the 1930s. A rectifier is an electrical device that converts Alternating current (AC to Direct current (DC a process known as rectification. The 1930s were described as an abrupt shift to more radical and conservative lifestyles as countries were struggling to find a solution to the Great Depression. Invented by Joseph Slepian while employed by Westinghouse, Westinghouse was the original manufacturer and owned trademark rights to the name "Ignitron".

It is usually a large steel container with a pool of mercury in the bottom, acting as a cathode. Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device A large graphite cylinder, held above the pool by an insulated electrical connection, serves as the anode. The Mineral graphite, as with Diamond and Fullerene, is one of the Allotropes of carbon. An anode is an Electrode through which Electric current flows into a polarized electrical device An igniting electrode (called the "ignitor") is briefly pulsed to create an electrically conductive mercury plasma, triggering heavy conduction between the cathode and anode. An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound

Ignitrons were long used as high-current rectifiers in major industrial installations where thousands of amperes of AC current must be converted to DC, such as aluminum smelters. An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant Direct current ( DC) is the unidirectional flow of Electric charge. WikipediaNaming Large electric motors were also controlled by ignitrons used in gated fashion, in a manner similar to modern semiconductor devices such as silicon controlled rectifiers and triacs. An electric motor uses Electrical energy to produce Mechanical energy. A silicon-controlled rectifier (or semiconductor-controlled rectifier) is a four-layer solid state device that controls current. A TRIAC, or TRIode for Alternating Current is an electronic component approximately equivalent to two Silicon-controlled rectifiers ( SCRs Many electric locomotives used them in conjunction with transformers to convert high voltage AC from the catenary to relatively low voltage DC for the motors. A locomotive is a railway Vehicle that provides the motive power for a Train. A transformer is a device that transfers Electrical energy from one circuit to another through inductively coupled Electrical conductors In Physics and Geometry, the catenary is the theoretical Shape of a hanging flexible Chain or Cable when supported at its ends and

Because they are far more resistant to damage due to overcurrent or back-voltage, ignitrons are still manufactured and used in preference to semiconductors in certain installations. For example, specially constructed pulse rated ignitrons are still used in certain pulsed power applications. Pulsed power is the term used to describe the science and technology of accumulating Energy over a relatively long period of time and releasing it very quickly thus increasing These devices can switch hundreds of kiloamperes and hold off as much as 50,000 volts. The anodes in these devices are fabricated from a refractory metal, usually molybdenum, to handle reverse current flow during ringing (or oscillatory) discharges without damage. A refractory is a material that retains its strength at high Temperatures ASTM C71 defines refractories as "non-metallic materials having those chemical and physical Molybdenum (məˈlɪbdənəm from the Greek word for the metal " Lead " is a Group 6 Chemical element with the symbol Mo Electricity In electrical circuits ringing is an unwanted Oscillation of a Voltage or current. Pulse rated ignitrons usually operate at very low duty cycles. In Telecommunications and Electronics, the term duty cycle is used to describe the fraction of time that a system is in an "active" state They are often used to switch high energy capacitor banks during electromagnetic forming, electrohydraulic forming, or for emergency short-circuiting of high voltage power sources ("crowbar" switching). A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors Electromagnetic forming ( EM forming or Magneforming) is a type of high energy rate metal forming process that uses Pulsed power techniques A crowbar, active crowbar or crowbar circuit is an Electrical circuit used to prevent an overvoltage condition of a Power supply unit from damaging

In electrohydraulic forming, an electric arc discharge is used to convert electrical energy to mechanical energy. A capacitor bank delivers a pulse of high current across two electrodes, which are positioned a short distance apart while submerged in a fluid (water or oil). The electric arc discharge rapidly vaporizes the surrounding fluid creating a shock wave. The workpiece, which is kept in contact with the fluid, is deformed into an evacuated die. A schematic illustration of the electrohydraulic forming process is shown in Fig. 1.

The potential forming capabilities of submerged arc discharge processes were recognized as early as the mid 1940s. During the 1950s and early 1960s, the basic process was developed into production systems. This work principally was by and for the aerospace industries. By 1970, forming machines based on submerged arc discharge, were available from machine tool builders. A few of the larger aerospace fabricators built machines of their own design to meet specific part fabrication requirements.

Electrohydraulic forming is a variation of the older, more general, explosive forming method. The only fundamental difference between these two techniques is the energy source, and subsequently, the practical size of the forming event.

Very large capacitor banks are needed to produce the same amount of energy as a modest mass of high explosives. This makes electrohydraulic forming very capital intensive for large parts. On the other hand, the electrohydraulic method was seen as better suited to automation because of the fine control of multiple, sequential energy discharges and the relative compactness of the electrode-media containment system. (metalformingmagazine. com)

See also