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  1. duke37

    line voltage

    Yesterday the 230V supply was 245V here. It depends on whether the loading is high and whether the wind is blowing. The official supply here is 230V+10% -6% so 216.2V to 253V.
  2. duke37

    How to build SMPS

    A Si iron core will permit a high flux to be used but loses power in Eddy currents. Powdered iron core can reduce the loss but the permeability will be much lower. Ferrites have a very high resistance so lower eddy current loss and can be run at high frequency, enabling fewer turns and lower...
  3. duke37

    Choosing Wire Gauge

    Hop "The longer the wire, the hotter it will become for any given current." I think not, the longer wire will have a bigger cooling area, the temperature will depend on the current but not the length. Trevor
  4. duke37

    Sensor for solar irradiance

    I wonder if you could use two plates, one temperature controlled and the top one open to the sun. Measure the temperature difference to get the thermal flux.
  5. duke37

    Capacitors of different capacity in series

    If you have a 1/X button on your calculator, this comes in handy to calculate capacitors in series or resistors in parallel. In reverse Polish, which I prefer:- 2 1/x 0.47 1/x + 1/x Shows 0.381
  6. duke37

    Capacitors of different capacity in series

    Add the reactances for series connection. So 1/C = 1/2 + 1/0.47 to give C in μF. Do not put more than 1kV on the pair since the voltages may not be shared as you might expect due to leakages.
  7. duke37

    Voltage rating of wire

    Yes, I did not describe the wire diameter in a clear way. Harald is better at english than most native speakers. Interestingly, car starter connectors are always known as cables not wires. I think that the insulation of the wiring of cars or combine harvesters has to not only provide isolation...
  8. duke37

    Voltage rating of wire

    If you look at the wires in a telephone cable you will see that they are fairly thin. Mains cables are thicker and have a secondary insulation layer. Car ignition cables are much thicker than either. It is all due to the voltage in the wire. Polyethelene is a common insulation, if you are rich...
  9. duke37

    Need help with circuit design

    A capacitor would do it but at 30A it would be enormous. You would need to bypass the charging resistor after a suitable time. If you did not use a charging resistor, then you would probably melt the switch. The same principle is used for the PWM controllers to raise the current but the charging...
  10. duke37

    2 motors pushing an object. 1 motor goes bad... other keeps going... object breaks???

    The motors must be connected the right way round whether in parallel or series to get them going in the same direction. You can test on 12V when the motors should run but slower.
  11. duke37

    Neon lamp for turntable repair

    Alternatively, use another string of leds connected in inverse across dorke's string. Then the rectifier will not be needed.
  12. duke37

    Where could I find a low RPM high torque motor?

    2kW is quite a chunky motor. There are 746W in one horsepower (UK).I assume it is driven from the mains and the motor will probably run at 2800 rpm in the UK. It will therfore be geared down a lot to reduce the speed and increase the torque. Power is torque times speed so you can work out the...
  13. duke37

    Testing Transistors With Digital and Analogue Multimeters.

    Because of the circuit in the analog meter, The red lead is negative. Doubtless this simplifies the switching.
  14. duke37

    Neon lamp for turntable repair

    I would think that if they were fed with a fairly high voltage which was backed off with a zener so that only the peak voltage was used, they would be quite good. Could Alec do a simulation?
  15. duke37

    Neon lamp for turntable repair

    That does not look like the original. You can get very powerful leds which could be supplied from a low voltage winding if you cannot get the original neon.
  16. duke37

    Output of the alternator

    The alternator can produce so many volts and so many amperes. The product of these is VA. The alternator limit will be the current which will heat the windings but the volts will be fixed. You mentioned power factor in #1. The power is VA times the power factor. Since the power factor has a...
  17. duke37

    Soldering Iron Catalyst

    Chop a bit off your tiara. :) I would guess that the wire is something cheap, plated with a very thin layer of platinum. Surface area is required.
  18. duke37

    Soldering Iron Catalyst

    My soldering irons use a heater to heat a rod of copper. The self igniting torches use platinum as a catalyst which is also used in the exhausts of cars. Do not put any platinum near a lead acid battery.
  19. duke37

    Output of the alternator

    VA is volts times amps. It only means watts power when the power factor is the maximum of 1. Thus 7kVA may be produced by 5kW
  20. duke37

    2 motors pushing an object. 1 motor goes bad... other keeps going... object breaks???

    Floating means that the power supply has no connection to 'earth'. This means that it can supply its voltage, in this case 12V, from a different reference. Consider a stool 12 inches high, you can put another stool on top to give a total height of 24 inches but this cannot be done if the top...
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