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  1. CarlPugh

    Saving 2D drawing as ***.DWG

    Is ***.DWG the most common file extension when dealing with vendors? If ***.DWG is not the most common file extension, what is the most common file extension? Have AutoSketch 9 and it isn't saved correctly to ***.DWG. Have TurboCAD Designer 17.2 and find it difficult to use. Which 2D program...
  2. CarlPugh

    Thermal rise calculation for a DC Electromagnet

    How is the heat getting out of the coil? Radiating out the sides of the coil? Conducted through the core the coil is wound on? Conducting through whatever the coil is mounted on? The easiest way to design a coil like this is to measure the temperature rise of a coil that you have made. Merely...
  3. CarlPugh

    Overcoming the Obstacle of Subjective Procedures

    The real question is does your colleague believe that you provide inadequate documentatin or is your colleagure playing office politics. If your colleagure believes that you are providing inadequate documentation, then discuss what should be documented with your colleague and with your boss...
  4. CarlPugh

    Determining coil characteristics

    Test the same as you would test the ratio of a transformer. (Which it is when the additional turns are added) Wind the 10 turns on. Assemble the core. The solenoid should be closed for all tests. Apply 1/4 rated coil voltage to the molded coil. Measure the voltage of the molded coil and the...
  5. CarlPugh

    Determining coil characteristics

    If the solenoid was originally designed for 60 hertz, Wind say 10 turns over the coil. Use small wire say #30 film insulated. Put the original steel back in the solenoid with the solenoid closed. Excite the coil at some low voltage. Use 60 hertz line and the original coil. Measure the voltage of...
  6. CarlPugh

    Solenoid control circuit

    DC solenoids usually require a high voltage to pull in and a lower hold voltage to prevent the solenoid overheating. A transistor is frequently used to apply full voltage for say 300 millisecond and then turn the voltage on and off at a high frequency to obtain a lower average voltage. Ross...
  7. CarlPugh

    secondary current

    3 amp continous from a 2 amp transformer. Not advisable. 8 amp for short periods. Some small transformers will handle this, and some transformers output voltage will drop drastically.
  8. CarlPugh

    AC to DC

    Buy a DC welding machine. A new machine will cost less and work better than trying to rework an AC welder. The DC welding machine's AC characteristics are critical in how well the welding machine welds. When Glenn Pacific was building welders, the procedure was to design the welder and then...
  9. CarlPugh

    Electronic Design Consoltation

    Medical equipment have their own standards. Get copies of all medical standards that apply to the product that you intend to manufacture. Read all the appliciable standards before designing anything.
  10. CarlPugh

    Generator refurbishment

    Back when I was designing transformers, the maximum dryout temperature was something under 100degC. The thinking was that if temperature got over 100degC, any moisture would turn to steam, and the pressure of the steam would damage the insulation.
  11. CarlPugh

    electromagnet A/turn

    Use square or rectangular wire. (or maybe copper strip) This will give the largest % copper fill. Square or rectangular wire is difficult to wind in the smaller sizes, so a fairly large size wire is prefered for winding. Size the wire to obtain the correct resistance for the power supply that is...
  12. CarlPugh

    Electromagnet: lamination vs. solid core

    A pulse is not DC. What is the width of your pulse? For short pulse widths (Say under 8 millisecond) a laminated core is usually advisable.
  13. CarlPugh

    High Power water capacitors

    Water capacitors were researched many years ago and there were papers written on using water capacitors. The secret to using water capacitors was to charge the capacitors up fast and immediately discharge them. If the capacitors were charged too long an explosion would result as mentioned by...
  14. CarlPugh

    Partial discharge test for oil cooled transformers

    Have made many partial discharge tests of oil cooled and dry type transformers to 60 kV RMS. (test equipment limitation) When testing dry type transformers, the partial discharge start voltage is very repeatable. When testing oil cooled transformers, if the test voltage is held for any length of...
  15. CarlPugh

    Hermetically sealed transformer calculation

    Have worked at 3 companies that made oil cooled/insulated transformers. The policy at all three companies was to have 10% air space at 25 deg C. Transformers were 65 deg C rise. 10 PSI pressure relief valves were used. Mineral oil was used. There were never any problems. If the inside height of...
  16. CarlPugh

    insulating varnish

    The nails in wood gave repeatable results. The arc was through the air. (Except when paint with carbon black was used) It has been some time since the tests were performed, but the way I remember it, is that we painted the dry wood and then drove nails into the wood. Probably the moisture was...
  17. CarlPugh

    insulating varnish

    The rule of thumb for insulation is when the voltage is doubled, the insulation thickness has to be three times as thick. Where there is a volts/mil rating for insulation, the rating is usually for a specific thickness of insulation under specific test conditions. (shape of electrode...
  18. CarlPugh

    Designing a high frequency magnet.

    Does the frequency have to be continously adjuatable or can it be in steps?. Steps where the magnet is turned off and the capacitance is changes for a different frequency is much easier. (If frequency does not have to be exact) High current operation requires that skin effect be taken into...
  19. CarlPugh

    Designing a high frequency magnet.

    Steel jacket on electromagnet at 1 KHz is bad news. You will probably have to design an electromagnet. Make decision on core. Possible candidates are 2 mil silicon steel, metglas, nickel iron or ferrite. I would start with ferrite. My belief is that it's easier to work with, more readily...
  20. CarlPugh

    Aluminium or copper in transformer windings?

    History keeps repeating itself. 36 years ago there was a shortage of copper and we converted the transformer designs to aluminum. There was no major problems. The two problems with aluminum compared to copper is the difficulity connecting to the aluminum and the fact that mechanically aluminum...

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