How do I wire a toggle switch for an HF amplifier power supply ?

Discussion in 'Amateur Radio Amplifiers' started by KC5SCK, Jun 17, 2017.

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  1. SM0AOM

    SM0AOM Ham Member QRZ Page

    I had the fortune of attending the Electricity History classes of Prof. Stig Ekelöf in the late 70's.
    He was an authority in this subject, and had a renowned research library with most of the famous works on electricity.

    Two of his lectures were devoted to Edison and his early systems, and on the "War of the Currents".

    The reasons behind the adoption of first 110V DC and later 110V AC were elaborated in some detail,
    and efficiency aspects were quite low on the priority list, as Edison envisioned a steam powered generating plant at
    small distances. As long as the electricity consumers were small scale lighting and the occasional DC motor this worked

    However, large installations of incandescent lamps at 110 V consumed impractical amounts of current, and also the beginning electrification of industrial plants so the voltage was doubled using the grounded centre-tap system. This became the norm for larger distribution systems.

    Tesla and Westinghouse had early understood the practical advantages of AC high-voltage distribution where the distribution losses were minimised, and the poly-phase self-starting induction AC motor devised by Ferraris and Wenström could operate directly from 3-phase distibution with a suitable transformer in between.

    This type of motor was so economical and robust that it could easily be incorporated into industrial machinery, replacing the belt-distributed
    steam-engine power in mills and plants. It also permitted the electification of agricultural processes due to its robustness.

    DC and locally generated low-voltage AC distribution in large scale became a quite short parenthesis in Europe.
    Some of the earliest distribution systems were DC,but were quickly replaced by AC when the installed consumer base grew.

    Other aspects were that power distribution usually were owned by public companies, or in rural areas by cooperatives, that bought and traded electrical power between them at an early stage. The concept of a "National Grid" caught on early. In the larger cities, the municipalities owned both generation and the distribution, and often built large-scale hydroelectric power-plants in rivers quite far, sometimes many 100's of km, away. This necessitated high-voltage transmission at an early stage.

    Already in the 1910's, 80 and 130 kV AC transmission systems were built. Some cities still used 220/440V DC local distribution as a stop-gap measure, and they used AC high and medium voltage feed to sub-stations, where mercury arc rectifiers produced the DC feeds to the subscribers.

    Regarding the choice of AC frequency, efficiency reasoning for large-scale operations came in early.
    Frequencies ranged from 25 to 65 Hz in early systems, but it turned out in the 1890's that the amount of copper, iron and its quality necessary in the windings and cores of motors and transformers had a shallow optimum around 50 Hz. Synchronised operation of large-scale plants also necessitated a common line frequency.

    The choice of 60 Hz by early US systems also became derived from the balance between copper and iron losses, that had a minimum around 60 Hz at the time. Before large-scale AC hydroelectric plants with their distribution systems were built in Europe, the transformer iron properties had improved somewhat, which shifted the optimum frequency somewhat downwards.

    WA7PRC likes this.
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    0 Hz. DC ? :oops:

    That was good info. Thanks.

    I think DC was tried at first. It was hard to transmit very far, And voltage drop killed it.
  3. AF6LJ

    AF6LJ Ham Member QRZ Page

    That was a good read thanks.
  4. WE6C

    WE6C Ham Member QRZ Page

    AF6LJ likes this.
  5. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Great read, as usual, Karl-Arne.

    The interesting thing about power transmission is that HV DC is making big splash now that there are methods to switch it to AC at the destination. Losses are low enough in the medium and long haul to make up for the switching expenses. Grid synchronization is easier, underwater cable losses due to capacitance are not an issue, etc.
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    This is turning back into a good thread after all.
    Thanks Karl-Arne.
  7. SM0AOM

    SM0AOM Ham Member QRZ Page

    Yes, HVDC certainly has closed in on the AC distribution.

    Modern HVDC systems are almost as efficient as AC, due to improved rectifiers and inverters. Interesting enough, HVDC was considered as early as the 1950's for building two large-scale systems for linking the hydro-electric plants in the north with population centres in the south.

    However, the current state-of-the-art for especially high-voltage mercury thyratron inverters was not considered proven enough to be used, so the systems were instead built using 380 and 400 kV AC distribution techniques.

    But only a few years later, a pioneering undersea-cable HVDC system was built between the mainland and the island of Gotland. It helped to mitigate the power generation and distribution problems on the island that was previously plagued by the effects of under-dimensioned ,local steam-powered electricity production. It became a huge success, and has since been upgraded with higher-performance rectifiers and inverters so its capacity now is several times the original.

    Incidentally, I have a loose personal connection to this project. My late father, that was a building contractor,
    performed his first large project in conjunction with construction works for the Gotland cable around the time I was born.

    KD2ACO, WA7PRC and AF6LJ like this.
  8. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    ... took a few pages... :p
    AF6LJ likes this.
  9. AF6LJ

    AF6LJ Ham Member QRZ Page

    Yup but hey..
    This is The Zed :)
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'm AC all the way, but have a few friends who are DC, and even AC-DC.

    I'm now using A/C that is powered by AC.

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