Thanks for your question. The 50kV AC suppy is transformed to 2.3kV and 3phases are converted to 2 phases by a Scott-connection ( en.wikipedia.org/wiki/Scott-T_transformer), which is the required supply to the main drive motor. The 2.3kV 2ph is also transformed to 440V 3ph for the supply to various drive motors in the auxilliary equipment. Here are two rotating converters that can produce 500 VDC and 125/250VDC, where the alternating current is rectified by means of a commutator, which allows direct current to be extracted from the rotor (en.wikipedia.org/wiki/Rotary_converter). Fredrik / Alexander association

@@AlexanderSAQ Thank you. Rotary converters are fascinating pieces of equipment. They were used quite a bit in early transit systems to convert 3 phase AC to DC for third rail power.

@@AlexanderSAQ So the motor spinning the HF alternator is an AC motor? How do you adjust the speed of the drive motor to adjust the transmission frequency? It also makes sense to me that a country like Sweden with a small population and relatively little international commercial activity could get by with one transmitting frequency. How about large generators of telegrams like the U.K. or the US?

@@Pamudder Thanks for your questions. To maintain a stable speed of the drive motor is a complex system. The voltage to the motor can be controlled between 1300 and 2300 VAC by using a Transductor, which is an adjustable choke coil, where the magnetic saturation of the metal core is adjusted with short pulses with 500VDC. The pulses are generated by the automatic speed control system which is chopping the field current to the 500VDC converter. Then the rotor of the drive motor is open in three phases. The resistance between the phases will determine the torque of the motor, and can be set using two separate liquid rheostats, one for key up and one for key down. At key down the latter is connected in parallell with the first, allowing for a lower resistance and thus more torque is applied to maintain the speed. Sweden had a massive emigration to the US, one of six moved during the hard years in the late 1800's and early 1900's creating a great need for communication. One can also think that the fact that the inventor, Ernst Alexanderson, was Swedish, played a role in the decision. Fredrik / Alexander association

@@AlexanderSAQ Thank you so much for the explanation.

I believe they said the 100th is in 2025. Watch it again.

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Here’s a simplified description of how the morse code is created when transmitting with SAQ: The Alexanderson alternator is supplying a magnetic flux with the frequency 17,200 Hz, or 17.2 kHz via 64 separate windings, each delivering 100V and 30A, which is led to two separate transformers in the high frequency amplifier. 32 leads are going to the first transformer and another 32 leads are going to the second transformer. Each transformer then has 32 individual primary windings, each of them electrically insulated from each other. 2000V is generated in the secondary winding of each transformer. The secondary windings from both transformers are connected in parallel and further connected to the antenna. However, there is also a third winding in each transformer, located between the primary and secondary winding. This winding can be supplied with 250V DC, 12A current (3kW), controlled by the morse key. When the morse key is up (no signal) the DC current is flowing through the third middle winding, reducing the amount of energy being induced from the primary to the secondary winding. At key-down, the current in the middle winding is blocked, and full power is induced into the secondary winding. So, at key-up there will be a very limited amount of energy going out into the antenna. The magnetic amplifier is simply “leaking” a little carrier wave, which can be detected if you have a sensitive receiver. In addition to the two transformers, there is a second system, also operated by the morse key, to alter the antenna resonance frequency. In the lower part of the “magnetic amplifier” two “transductors” are located. A transductor is a variable inductance, consisting of a primary winding for the AC and a secondary winding for DC, both placed around an iron core. The iron core works as an inductance for the AC winding, however when 250V 30A current is flowing in the DC winding, the iron core is magnetically saturated and thus reduces its inductance. The antenna is a resonant circuit with its resonance frequency set to 17.2kHz and the two transductors are connected inline with the antenna. This means that by key-up, the antenna is not tuned to the resonance frequency, due to the changed inductance in the two transductors. At key-down, the 250V 12A DC current is blocked, the inductance will be altered and the antenna will be in tune. Ernst Alexanderson invented this system, with all its components, to allow a relatively small DC current of 3kW to control a very large power of 200kW. Fredrik / Alexander association

The magnetic amplifiers or transductors are like a transformer but with a small iron core which can be saturated. The 17.2 KHz signal from the alternator is fed to the antenna via one if the windings. In this state the signal is blocked because the winding is acting as a choke. To turn on the signal (ie when pressing the morse key), a DC voltage is applied to the other winding. This saturates the iron core and since there is no inductance possible in the coil due to the core being saturated, it no longer acts as a choke and passes the alternator signal to the antenna. Hope that helps.