Thyristor power supplies.
The only low-frequency version I have met was when I was a Field Service Engineer, computer maintenance. Amongst the products that I serviced was a huge line printer (intended for use with mainframes) manufactured by an American firm: Printronix. Apart from the novel printing mechanics, the PSU (which featured a huge mains-isolating step-down transformer) used a thyristor-stabilised arrangement to produce +30v at about 15 amps for a huge set of solenoids and their drivers. The basic idea was that of the more conventional arrangement that we find in high-frequency switch-mode PSUs - but in this affair, the thyristor was switched at 50 Hz. Consequently, the series smoothing choke was enormous - as was the main filter capacitor: 0.1 Farad at 50 v working; about 12 inches high and about 5 inches in diameter. :s The recovery diode was mounted on a huge heat-sink also.
Needless to say, extreme care was required when working / servicing that beast: 30v d.c. regulated @ 15A capacity can do a lot of damage!
Moreover, I dread to think what the a.c. mains supply looked like, especially when about a dozen of these printers were going flat out! I do recall that the racket was absolutely deafening!
Al.
The only low-frequency version I have met was when I was a Field Service Engineer, computer maintenance. Amongst the products that I serviced was a huge line printer (intended for use with mainframes) manufactured by an American firm: Printronix. Apart from the novel printing mechanics, the PSU (which featured a huge mains-isolating step-down transformer) used a thyristor-stabilised arrangement to produce +30v at about 15 amps for a huge set of solenoids and their drivers. The basic idea was that of the more conventional arrangement that we find in high-frequency switch-mode PSUs - but in this affair, the thyristor was switched at 50 Hz. Consequently, the series smoothing choke was enormous - as was the main filter capacitor: 0.1 Farad at 50 v working; about 12 inches high and about 5 inches in diameter. :s The recovery diode was mounted on a huge heat-sink also.
Needless to say, extreme care was required when working / servicing that beast: 30v d.c. regulated @ 15A capacity can do a lot of damage!
Moreover, I dread to think what the a.c. mains supply looked like, especially when about a dozen of these printers were going flat out! I do recall that the racket was absolutely deafening! Al.
