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  • Users: BillJ
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  1. BillJ

    How to stop high dc currents...

    Sorry, the link didn't go all the way thru. Select the United States (map), Supplemental (top menue), Electrical Ratings (pull down menue).
  2. BillJ

    How to stop high dc currents...

    Here is a link on re-rating AC switches: http://us.switchzone.com/electrical.asp
  3. BillJ

    Testing of large capacitors

    For the capacitors in the power supply, a good test is to observe the power supply ripple. As electrolytics age, they dry out and capacitance decreases. This will show up as an increase in ripple. A change in the shape of the ripple could indicate leakage or breakdown.
  4. BillJ

    How long will a battery charge last?

    If you are referring to 300 cold cranking amps, the battery is probably only a 33 amp hour battery (approximately). At 3 amps (.09C rate) a new battery would be dead in about 10 hours. I probably wouldn’t want to go more then 2 hours if I wanted to start my car. A lot depends on how much...
  5. BillJ

    capacitance calculation

    See the thread "capacitance to resistance" in this forum
  6. BillJ

    capacitance to resistance

    If you know the Belden equivalent, they list the capacitance per foot for a number of their cables. I believe they have a catalog that you can down load
  7. BillJ

    TNT equivalent for energy released in electrical fault

    Stevenal, thanks for the web address. It's a neat program. Megaconverter II, http://www.megaconverter.com/mega2/, gives (under Energy) 1 Ton of TNT = 4.18*10**9 Joules which is about 4609 Joules/gram. Very close to Busbar's answer.
  8. BillJ

    overvoltage protection

    A common (and cheap) method of over voltage control, which is used in the input circuits of oscilloscopes, is a simple diode to each of the power supplies. The diodes are place to conduct if the signal exceeds the power supply by the junction voltage of the diode (about 0.7 for silicon...
  9. BillJ

    Switch contact ratings

    The switches (including those used in relays) are used in Elevator Controls and the switches and circuits are varied and from a number of manufacturers. The currents run from the milliamps to the 10’s of amps and the voltages from 12V to 240V AC or DC. The circuit types are either resistive...
  10. BillJ

    Switch contact ratings

    Does anyone have some formulas for calculating switch contact ratings? Something that would give me the breaking AC & DC voltage and current that the contacts would be expected to handle.
  11. BillJ

    capacitance to resistance

    If you are looking for capacitive reactance (effectively AC resistance), the formula is 1/2(PI)FC. PI = 3.14.... F = frequency in Hertz (or Cycles Per Second) C = capacitance in Farads A 1uF capacitor would have a reactance of about 2653 ohms at 60Hz.
  12. BillJ

    Need to calculate relay coil voltages.

    I am trying to find a method of calculating the operating voltage of a series of relay coils. These relays/coils are drop in replacements for Otis Elevator controllers. The relays are used for energizing elevator door motors, the elevator motor, releasing the elevator brake, just about...
  13. BillJ

    Relay voltage specification

    I am trying to find a method of calculating the operating voltage of a series of relay coils. These relays/coils are drop in replacements for Otis Elevator controllers. The relays are used for energizing elevator door motors, the elevator motor, releasing the elevator brake, just about...
  14. BillJ

    Relay voltage specification

    I have the manufacturing data on several relays (coil windings, wire gauge, core type, etc.)used in elevator controls. Is there a way to estimate the voltage they were intended to work at?

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