Industrial triodes
Frequently asked questions about triodes
Conceived and perfected at the beginning of the 20th century, the triode is an electronic signal amplification device that is at the origin of talking pictures, wireless transmission (radio communication), radar, television, computers and the latest generation of telecommunications. The vacuum diode, which creates a unidirectional current, may not be the first type of electronic tube, but it is at least the first to use radio waves to transmit a signal.
What is a triode?
Born under the name of audion in 1906, the triode is a vacuum lamp (electron tube) made up of three different electrodes: the emitting cathode, the intermediate grid and the receiving anode.
- A hot electron emitter, the cathode consists of an incandescent filament or a plate heated by such a filament. This temperature rise gives electrons the energy they need to free themselves from the support and form an electron cloud around the cathode.
- Applying an electrical potential difference of between the cathode and the anode accelerates the movement of electrons towards the anode. This results in a current of a few milliamps in the electronic circuit.
- By interposing a grid between the two electrodes, the potential can be modulated to restrict or promote the passage of electrons. A small variation in electrical potential on the grid results in a large variation in the current collected by the anode, according to the principle of amplification.
The triode works like a switch on the ” all or nothing ” principle, and enables significant amplification of the electronic signal without generating distortion effects.
What types of triodes are used in industry?
Vacuum tubes, which were at the origin of radio communication in the 1920s and computing in the 1940s, were replaced in the 1960s by a new type of electronic component: the transistor. This semiconductor device with three active electrodes replaced the vacuum lamp in telecommunications, electronics and computing. Only a few sectors, such as machine tool construction, continue to use triodes because of their ability to amplify high power (up to over 150 MHz) in the absence of any neutrodyning effect. Triodes are also used in welding presses based on high-frequency technology.
What types of machines use industrial triodes?
Generally speaking, all machines and equipment using high-frequency technology are equipped with high-power amplifiers in the form of a common-grid triode or a common-pentode cathode to generate waves up to 100 MHz. High-frequency waves can be used to modify the state of matter by raising the temperature of electrons. Depending on the equipment used, it is then possible to cut, weld, glue, connect, dry or dehydrate materials according to their physico-chemical characteristics. Triodes with high amplification power are used in welding presses for plastics and even certain metals (induction), thermoforming machines, cold-cutting machines for tubes, gluing machines for wood, dryers and dehydration equipment for organic materials…
What makes up a high-frequency generator?
On an HF welding press, the generator is responsible for transforming electrical energy into high-frequency waves to power the electrodes. Incorporated into the machine frame, it is made up of the following components:
- a electron tube or high-frequency triode ,
- a triode cooling circuit,
- a current galvanometer for the anode,
- an anode circuit breaker.
- a water-cooled or forced-air-cooled heat sink
- an oscillator for quarter-wave HF energy transfer,
- a motorized variable capacitor for high-frequency adjustment,
- automatic HF power regulation at 27.12 MHz,
- an anti-flash device electronically sensitive thyristor,
- a shielded high-frequency line.
How do I make the triode last on an HF welding machine?
For high-frequency soldering presses, the electronic tubes are among the wear parts with the highest renewal or replacement costs. It is therefore essential to maximize the precautions taken when using triodes, in order to optimize their potential lifespan through a few common-sense measures:
- Observe a minimum warm-up phase of ten minutes at the start-up of the welding machine before starting product assembly operations.
- After completing a sequence of welding operations, it’s best to let the diode cool down for about a quarter of an hour before shutting down the press.
- Ensure that filters are cleaned on a regular basis, with the frequency depending on the level of dust in the production environment (weekly, fortnightly, monthly, etc.).
