CAPACITORS - AMS Technologies

www.amstechnologies.comCurrent/VoltageMaximum operating current for vacuum capacitors is limited by temperaturerise and working voltage. At lower frequencies, a capacitor is a current-limitingdevice as a result of its capacitive reactance. At some frequencies, the internalgeneration of heat exceeds the device’s heat-sinking capabilities, and itscurrent-carrying capacity is limited by thermal considerations. A currentvs. frequency chart is provided for each capacitor listed.Peak voltage is limited by mechanical design of the capacitor. It does not varywith frequency.TemperatureJennings Technology vacuum capacitors are designed to meet MIL-C-23183specifications. Our capacitors are rated for a maximum operating temperatureof 125°C (257°F) with normal convection cooling at an ambient temperatureof 25°C (72°F).CurrentThe current rating provided in the tables in this catalog is the maximumcurrent the vacuum capacitor at maximum working voltage can handlecontinuously under normal convection cooling at an ambient temperatureof 25°C.Pulse Ratings — Continuous RF current ratings may be exceeded for shortperiods if the working voltage rating is not exceeded. This applies particularlyto pulse and peaks-of-modulation applications. Momentary currents mayexceed the catalog continuous current rating by a factor of the square rootof the duty cycle, provided the working voltage is not exceeded.High-current applications?Jennings PV Series capacitors set a newstandard for vacuum variable capacitors.One of the latest innovations to emerge fromJennings Technology, the PV Series of vacuumvariable capacitors was designed to withstandrugged, high-current environments to meetthe increasing demands of semiconductorprocessingapplications.Jennings quality engineers put the PV Seriescapacitors through rigorous testing. All testedunits achieved more than 2.5 million cycleswhile still meeting their original specifications,and many exceeded 3.8 million cycles.For detailed test results, contact Jenningsat 408-292-4025 or visit www.jenningstech.com/technotes/high_ratings.shtml.Jennings offers PV Series vacuum variablecapacitors in 500, 1000 and 2000pFcapacitance. Look for them on pages 23,30 and 35 of this catalog.Amplitude Modulation Ratings — Capacitors in AM service must be ableto withstand peaks-of-modulation voltage and current.Current ratings are based on temperature, so the heating effects of themodulated currents determine the capacitor requirements.The average output power of an AM transmitter that is 100% sine wavemodulated is 1.5 times the unmodulated carrier power. The average modulatedcarrier current is 1.225 times the unmodulated carrier current. Therefore,a capacitor current rating of 1.2 times the carrier current will be sufficient,even though the peaks-of-modulation currents are twice the carrier current.w w w . j e n n i n g s t e c h . c o m | 4 0 8 - 2 9 2 - 4 0 2 5 5