induced drag (aerodynamics). Aerodynamic drag produced by an airfoil when it is producing lift. The amount of induced drag is determined by the shape and the area of the airfoil, the angle of attack, the air density, and the speed of the air moving over the airfoil.
induced voltage. Voltage generated in a conductor when it is cut, or crossed, by lines of magnetic flux. There are three ways a conductor can be cut by lines of magnetic flux: (1) The conductor can be held stationary and the magnetic field moved back and forth across it. (2) The conductor can be moved back and forth through a stationary magnetic field. (3) Both the conductor and the magnetic field can be held stationary, but the magnetic field can be produced by alternating current, which constantly changes its direction and strength.
inducer (turbine engine component). Rotating inlet guide vanes installed on the center of a centrifugal compressor to pick up the inlet air and direct it at the correct angle into the impeller blades.
inductance. The electrical characteristic of a conductor which causes a voltage to be produced when it is cut, or crossed, by lines of magnetic flux. The basic unit of inductance is the henry. See henry.
inductance bridge (electrical measuring instrument). A bridge-type precision instrument used to measure an unknown inductance by comparing its inductive reactance at a specific frequency with that produced at the same frequency by an accurately known inductance.
induction compass. See earth induction compass.
induction furnace. An electric furnace in which the metal to be melted is heated by the induction of high-frequency electromagnetic energy.
induction heating. A method of heating an electrically conductive material by inducing alternating current into it. The rapidly reversing current causes the material to get hot.
induction motor. A type of alternating current motor in which the line voltage is connected across stationary windings in the motor housing. The rotor of an induction motor is made in the form of a “squirrel cage.” Bars of copper or aluminum are embedded in slots in a laminated soft-iron core, and are welded to heavy copper or aluminum plates on each end of the core. There is no electrical connection to the rotor.
The stator winding serves as the primary of a transformer, and the bars and end plates of the rotor act as the secondary. Current induced into the rotor bars causes a magnetic field that reacts with the field of the stator, and this reaction causes the rotor to turn. The magnetic field of the stator of a single-phase induction motor does not rotate, but rather it pulses on and off. A separate start winding is wound in the stator to produce a rotating field for starting a single-phase motor. The phase of the current in the start winding is shifted by a capacitor or inductor so that it is different from the phase of the current in the run winding. This shifted phase produces a rotating magnetic field.