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Limitations in operating conditions
1. In attempting to operate tubes at high power, certain limitations are encoun-
tered. One of these is the peak emission current; it represents the maximum rate at
which electrons can be given off without harm to the cathode structure, and without
causing harmful increase of voltage drop within the tube.
2. Another limitation is the peak inverse voltage, or the maximum voltage that
can be impressed across the tube elements without causing failure, either by electrical
breakdown or by ionization of the gas within the tube.
3. The third important limitation is plate dissipation. When an electron arrives
at the plate, its kinetic energy is transformed to heat and serves to raise the tempera-
ture of the plate structure. If the temperature goes too high the plate may melt, or
electron emission from the plate may take place. Many high-power transmitting tubes
have heat-radiating fins attached to the anode for the purpose of transferring heat
generated at the plate as quickly as possible to the surrounding air; others are de-
signed to permit water circulation around the anode structure.
4. The maximum amount of heat that can be safely dissipated by the plate of
any tube is stated in terms of the corresponding electrical power, in watts, and is re-
ferred to as the maximum plate dissipation. With tubes containing grid structures, the
heating of each grid must also be taken into account.
5. A triode is a tube which contains a third element, the grid, located between
cathode and plate. The grid usually takes the form of a helix or spiral of fine wire, so
that electrons may pass freely through it. Since the grid is nearer to the cathode, the
potential of the grid has a greater effect in controlling electron flow than does the
plate potential. If the grid potential is negative with respect to the cathode, as is usu-
ally true, electrons will not be attracted to the grid itself, and there will be no grid cur-
rent.
11.6 Переведите словосочетания
a) peak emission current; cathode structure; voltage drop; plate dissipation;
high-power transmitting tubes; heat-radiating fins; water circulation; grid structure.
b) the heating of each grid must be taken into account; within the tube; across
the tube elements; without causing harmful increase of voltage drop; in terms of
variations of the grid potential.
11.7 Ответьте на вопросы
1. What is the peak emission current? 2. What is the third important limitation?
3. When may electron emission take place? 4. What is referred to as the maximum
plate dissipation? 5. What is a triode? 6. When will there be no grid current?
11.8 Переведите предложения
1. If the temperature goes too high, electron emission from the plate may take
34
Limitations in operating conditions 1. In attempting to operate tubes at high power, certain limitations are encoun- tered. One of these is the peak emission current; it represents the maximum rate at which electrons can be given off without harm to the cathode structure, and without causing harmful increase of voltage drop within the tube. 2. Another limitation is the peak inverse voltage, or the maximum voltage that can be impressed across the tube elements without causing failure, either by electrical breakdown or by ionization of the gas within the tube. 3. The third important limitation is plate dissipation. When an electron arrives at the plate, its kinetic energy is transformed to heat and serves to raise the tempera- ture of the plate structure. If the temperature goes too high the plate may melt, or electron emission from the plate may take place. Many high-power transmitting tubes have heat-radiating fins attached to the anode for the purpose of transferring heat generated at the plate as quickly as possible to the surrounding air; others are de- signed to permit water circulation around the anode structure. 4. The maximum amount of heat that can be safely dissipated by the plate of any tube is stated in terms of the corresponding electrical power, in watts, and is re- ferred to as the maximum plate dissipation. With tubes containing grid structures, the heating of each grid must also be taken into account. 5. A triode is a tube which contains a third element, the grid, located between cathode and plate. The grid usually takes the form of a helix or spiral of fine wire, so that electrons may pass freely through it. Since the grid is nearer to the cathode, the potential of the grid has a greater effect in controlling electron flow than does the plate potential. If the grid potential is negative with respect to the cathode, as is usu- ally true, electrons will not be attracted to the grid itself, and there will be no grid cur- rent. 11.6 Переведите словосочетания a) peak emission current; cathode structure; voltage drop; plate dissipation; high-power transmitting tubes; heat-radiating fins; water circulation; grid structure. b) the heating of each grid must be taken into account; within the tube; across the tube elements; without causing harmful increase of voltage drop; in terms of variations of the grid potential. 11.7 Ответьте на вопросы 1. What is the peak emission current? 2. What is the third important limitation? 3. When may electron emission take place? 4. What is referred to as the maximum plate dissipation? 5. What is a triode? 6. When will there be no grid current? 11.8 Переведите предложения 1. If the temperature goes too high, electron emission from the plate may take 34
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