Ionic Electric Drive
Ionic Electric Drive
a drive that consists of an electric motor and an ionic converter, which controls the motor’s operation. By changing the voltage applied to the motor, it is possible to change its speed of rotation and, therefore, to control the speed of the drive. The voltage can be changed in discrete steps (step regulation) by switching the taps of the matching transformer or continuously by changing the angle of conduction of the converter elements (valves) that pass the current from the supply system to the electric motor. The control voltage acting on the converter valves is supplied by the control unit. Thyratrons are generally used as converter valves in low- and medium-power ionic drives; ignitrons and excitrons are used in high-power drives.
A distinction is made between DC and AC ionic drives. In the first case the current passing through the converter is fed to the armature or excitation windings of a DC motor; in the second case the current is supplied to the stator or rotor windings of an asynchronous or synchronous electric motor. The converter element in a DC drive is made as a recitifier in a bridge circuit with a zero terminal. The converter of an AC circuit is a frequency converter built up in a rectifier-inverter circuit or as a circuit with direct coupling.
Ionic electric drives may be reversible (permitting a change in the direction of rotation of the motor) or nonreversible. A switching mechanism is generally used for reversing: in a DC drive it may be a mechanical reverser or an extra valve assembly; in an AC drive, a change in the phase sequence in the control unit.
Ionic electric drive is used in rolling mills, elevators, large fans, machine tools, and railroad locomotives. Since 1960, electric drives with semiconductor converters have been replacing ionic drives in medium-power equipment.
REFERENCESButaev, F. I., and E. L. Ettinger. Ventil’nyi elektroprivod. Moscow-Leningrad, 1951.
Chilikin, M. G. Obshchii kurs elektroprivoda, 4th ed. Moscow-Lenin-grad, 1965.
IU. M. IN’KOV