saturable reactor (electrical component). A type of electrical transformer whose core permeability is varied to control the current flowing in its secondary winding. A control winding carrying direct current is wound over the transformer core. When no current flows through the control winding, the permeability of the core is high, and the transformer has enough inductive reactance to decrease the secondary current.
When maximum current flows in the control winding, its magnetic field saturates the core with a steady magnetic flux. This flux decreases the permeability of the core so much that the changing flux caused by the secondary current does not affect the core. There is less inductive reactance, so the secondary current has less opposition, and it increases.
saturate (meteorology). To combine to such an extent that there is no more tendency to combine. Dry air absorbs water vapor. But when the air becomes saturated, it will not absorb anymore. The amount of water the air can hold before becoming saturated depends upon its temperature.
saturated adiabatic lapse rate (meteorology). The rate of decrease of temperature with altitude as saturated air is lifted with no gain or loss of heat from outside sources. The saturated adiabatic lapse rate varies with temperature, being greatest at low temperature.
saturated vapor. The condition of the vapor above a liquid that will not allow any more of the liquid to evaporate.
saturation (meteorology). The condition of the atmosphere when the actual water vapor present in the air is the maximum the air can hold at the existing temperature.
saturation current (electron control current). The plate current flowing in an electron tube circuit when all of the electrons emitted from the cathode are attracted to the plate. In a transistor circuit, saturation current is the current flowing between the emitter and collector when an increase in the forward bias between the base and emitter causes no further increase in the emitter-collector current.
sawtooth waveform. The waveform of voltage produced by a relaxation oscillator. The voltage across the capacitor in a relaxation oscillator rises relatively slowly because it flows through the series resistor. But, when the voltage rises to the ionization potential of the gas discharge tube, the tube fires and the voltage across the capacitor drops off immediately.
The slow rise and rapid fall produce a sawtooth-shaped voltage wave. See relaxation oscillator.