sine-wave alternating current. Alternating current whose waveform is that produced by a rotary generator. The instantaneous value of sine-wave voltage is found by multiplying its peak value by the sine of the angle through which the rotor of the generator has turned.
For example, when the rotor has turned 30° from the position in which it produces zero voltage, the instantaneous voltage is one-half the peak voltage (the maximum voltage it can produce). The sine of 30° is 0.5, or one-half. When the rotor has turned 45°, the instantaneous voltage is 0.707 time the peak voltage. The sine of 45° is 0.707. When all of the instantaneous values of sine-wave alternating current are plotted, a smooth sine curve results.
single-acting actuator (fluid power system). A type of actuator in a fluid power system that uses fluid under pressure to move it in one direction, but a spring to return it. Hydraulic brakes use single-acting actuators to move the brake shoes out against the rotating drum. Hydraulic pressure moves the shoes out, but a spring pulls them back when the brake pedal is released.