Most Frequently Asked Questions about Capacitors
<%=company%> is the largest designer and manufacturer of vacuum capacitors in the world. Jennings capacitors utilize vacuum and gas as the dielectric. There are fixed and variable capacitor models. Fixed capacitors are preset during production and remain constant through out their life. Variable capacitors utilize a specially designed mechanical interface that allows the capacitance to be varied throughout a preset range.
2. What range of capacitance do your products cover?
Jennings has the broadest product line offering of vacuum and gas filled capacitors. The fixed and variable capacitor models cover a capacitance range from 1pF up to 5000pF. With this variety of products, voltage and current levels also vary greatly with maximum values of 60 kV and 1000 amps. Operational characteristics will vary greatly depending on the capacitor design. Be sure to verify all operational specs and product specifications.
3. Why is there a difference between test voltage and working voltage?
Testing voltage is the maximum 60 Hz voltage that can be applied to the capacitor without breakdown occurring. Capacitors are tested at this voltage to determine the general condition of the capacitor. Working voltage is the maximum peak voltage that can be applied continually. A complete response to this question can be found in the Jennings TechNote C-2: "The Effects of Voltage on Vacuum Capacitors"
4. What's the reason for a vacuum dielectric?
A vacuum provides a dielectric constant that most closely achieves a value of 1. With such a dielectric Jennings capacitor designs can achieve the maximum voltage gradient per given space, thus enabling the smallest compact envelope.
5. Can you specify different capacitance vs. turns ratio?
Yes, capacitance vs. turns ratio can be changed for all variable capacitors. These changes can be implemented in the factory during original production of the capacitor. Jennings offers a variety of turning ratios for most of the variable capacitor designs. Please consult with our Sales Department for details.
6. What is the maximum temperature your capacitor specifications are based on?
The maximum temperature is based on MIL-C-23183 specifications. Most ceramic capacitors are rated a maximum temperature of 125ºC and glass capacitors at 85ºC. A complete response to this question can be found in the Jennings TechNote C-1: "Vacuum Capacitor Characteristics "
7. What is the average life of a Jennings capacitor?
The mechanical life of variable capacitors is related to length of stroke, speed of operation, bellows material, and application. Extensive mechanical life tests have been run and continue to run. Life test results are generally based off of a 50-75% stroke length and 200-300 rpm. A cycle is considered one complete back and forth rotation of the lead screw. The most recent capacitor designs are achieving approximately 3 Million cycles. Contact the Jennings Sales Department for details relating to the different capacitor models.
8. What standard options are offered on Jennings capacitors?
There are a variety of modifications and options available with Jennings capacitors. It is recommended that you consult with the Sales Department to determine the best options for your specific requirements. Some of the more popular options with our capacitors are: Non-magnetic versions, Mil-Spec qualifications, various turns vs. capacitance ratios, mounting thread type, and corona rings.
9. What is a Q factor?
The "Q" factor is the quality factor. It is a ratio of stored energy to dissipate energy. A complete response to this question can be found in the Jennings TechNote C-1: "Vacuum Capacitor Characteristics "
10. What's the standard warranty?
The standard warranty on all Jennings Capacitors and Relays is 3 years and 1 year for all contactors, interrupters and coaxials, from the date of manufacture.
The Warranty Policy is as follows:
Jennings warrants that, at the time of shipment, the products manufactured will be free from defects in material and workmanship and will conform to the specifications furnished by or approved, in writing, by Jennings.