Abstract :
Series-valve stabilizers are considered as a simple step-by-step development of the cathode follower. By shunting a resistor or barretter across the series valve, substantially constant loads of several amperes can be stabilized to ±0.01 per cent. For operation from a.c. mains, a heavy-duty d.c. power unit comprises a medium-power series valve stabilizer complementing an unstabilized rectifier and filter circuit. This latter supplies up to 95 per cent, of the load current, preferably through barretters. If the barretters precede the rectifier, a variable-ratio current transformer can be used to adjust their effective regulating current. Practical details of heater supply stabilization, protective delay circuits, and rectifier and filter economics are discussed. Full circuits are given of two typical units providing outputs of 250 and 500 watts with efficiencies of 35 and 65 per cent, respectively. The latter includes a device providing audible warning when supply-voltage variations exceed the range stabilized automatically.
