Short for Servo Motor or Servomechanism (see entries).

Technically, any motor equipped with a feedback device can be considered a servo motor. Most commonly though, the term refers to a low inertia type of motor designed for accurate and quick response for positioning applications.

A brushed-type DC servo motor operates much like a standard industrial DC motor. It has a wound rotor, permanent magnet stator and brushes and a commutator to switch windings as the motor rotates. Since the fields are fixed magnets, the speed range is limited from 0 to base speed, i.e., not constant horsepower above base speed.

The brushless servo motor uses a rotor with magnets, and the windings on the stator, or stationary part of the motor. This type of motor does not have a commutator, so in order to switch windings to keep it going, electronic commutation is used. This entails a sensor (encoder or resolver) on the motor that lets the amplifier know where the rotor is, and which winding should be switched on. This type offers reduced inertia, which results in better response and elimination of brush and commutator maintenance as well as more ability to handle more peak power and provide zero speed holding torque on a continuous basis.

Servo technology is commonly found in applications such as wire forming, including cut-to-length and spring forming, where small, fast, accurate movements are required. Multi-axis controllers can be programmed to command multiple servo amplifiers to provide accurately sequenced movements. Servo drives can be used for simple speed control applications where high accuracy is required, but the high initial cost makes AC Flux Vector drives a more attractive choice.

A feedback control system in which at least one of the system signals represents mechanical motion.

In cross-wire welding, the extent to which the wires are pressed together so the thickness of the weld is less than the combined diameter of the wires. Often expressed as a percentage of the set down of one wire. The amount of the set down is not necessarily a reliable measure of the strength of the weld or an indication that the fusion between the joint surface is good, for it may be achieved by high pressure at too low a temperature.

Designation for cable like type SE, Style U, service entrance cable.

Designations for silicone rubber insulated equipment wire.

Designation for silicone rubber insulated fixture wire, solid or seven-strand conductor, 200°C.

SF, but with flexible stranding, 150°C.

Designation for wire like SW but with ground wires (CSA).

Designation for wire like SWO, but with ground wires (CSA).

Designation for thermoplastic battery and booster cable.

Designation for thermoset (XLPE) battery and booster cable.

Designation for portable power mine cable, three or four individually shielded conductors, 5000V.

Designation for wire like SH-A, but shield is overall.

Designation for wire like SH-B, but with grounding conductors.

Designation for wire like SH-A, but with grounding conductors.

See Cable, Vertical Riser.