|
Thorough analysis of switching components market
shows that the existing switches (e.g. hot cathode pulse thyratrons,
spark gaps and ignitrons, vacuum modulator tubes as well as
solid state switches) are unable to meet all emerging requirements
of the cutting-edge pulsed power technologies. The primary
restriction is either considerable power losses caused by
high internal resistance in open condition (modulator tubes)
or sufficiently low service life of the switches (all the
rest). In terms of cumulative charge it comes to 1000-5000
C for spark gaps, 5*10e5 C for thyratrons and modulator tubes,
10e5 C for mercury ignitrons. The limits are defined by extremely
high erosion of electrodes, loss of emission of hot cathode
for pulse thyratrons, in ignitrons – destruction of anode,
contamination of mercury by products of anode erosion and
triggering system death. Another serious hindrance for wide
ignitron application is a mercury toxility. Also the most
deciding parameter is the cost of a tube, as the component
affordability is considerable requirement for technological
installations.
Competition of vacuum and gas-discharge tubes
with solid state switches without hot cathode resulted in
reduction of volumes of world production of thyratrons, gaps
and ignitrons. Meanwhile it is fully justified to change vacuum
and gas-discharge switches in microelectronics and in other
low-power devices, switching relatively low peak currents.
Besides high-voltage solid state assemblages are quite expensive.
Experts say that the significance and prospect of solid state
switches in high-power applications are overestimated. That
is why leading manufacturers of thyratrons and spark gaps
continue their research and development efforts in direction
of high-power switches including cold cathode thyratrons.
We think that there are a number of applications
where gas-discharge switches do not have real competitors.
So it was considered that the basic advantage of solid state
switches over gas-discharge is long life, high efficiency
(p-n voltage drop is 1.5 – 2.0 V whereas gas-discharge cathode
drop is 20 – 200 V), lack of incandescent cathode and circuits,
compactness and light-weight at the same cost and electrical
parameters. However, for currents over 1 kA and voltage >
5 kV with current rise rate 10e9 À/s there was only one advantage
– service life. Dimensions and weight must be increased due
to necessity to use serial connection of elements, constringent
magnets, water cooling, overvoltage protection and so on,
which results in reduction of efficiency and rise in price.
Meanwhile one thyratron is capable of providing the parameters
when commuting higher currents and its degree of efficiency
achieves 90-99 %.
Our pseudospark switches designated as TDI,
TPI and TPU have been developed since 1990. Now we have international
priority in this field. There are only two companies producing
direct analogues of TDI for currents up to 150 kA – British
e2v technologies inc (thyratron HX302) and ALSTOM Vakuumschalttechnik.
However in our opinion there is no full replacement of our
switches. TPI-thyratrons have no analogues worldwide absolutely.
|
|
Request 
