SERVOMECHANISM --A closed-loop
system that produces a force to position an object
a spinning body that causes it to oppose all
according to the information that originates at the
attempts to tilt it away from the axis in which it
input.
is spinning.
ROTATING FIELD --The magnetic field in
SERVOMOTOR --An ac or dc motor used in
a multiphase ac motor that is the result of
servo systems to move a load to a desired position
field windings being energized by out-of-phase
or at a desired speed. The ac motor is usually used
currents. In effect, the magnetic field is made to
to drive light loads at a constant speed, while the
rotate electrically rather than mechanically.
dc motor is used to drive heavy loads at varying
speeds.
ROTOR --(1) The revolving part of a rotating
electrical machine. The rotor may be either the
SERVO SYSTEM --An automatic feedback
field or the armature, depending on the design of
control system that compares a required condition
the machine. (2) The rotating member of a
(desired value, position, etc.) with an actual
synchro that consists of one or more coils of wire
condition and uses the difference to drive a control
wound on a laminated core. Depending on the
device to achieve the required condition,
type of synchro, the rotor functions similarly
to the primary or secondary winding of a
SHIELDING --(1) A metallic covering used
to prevent magnetic or electromagnetic fields from
affecting an object. (2) Technique designed to
SATURABLE REACTOR --A control device
minimize internal and external interference.
that uses a small dc current to control a large ac
current by controlling core flux density.
SHUNT --A resistive device placed in parallel
with another component. Appreciable current
SATURATION --The condition existing in
may flow through it, and an appreciable voltage
any circuit when an increase in the driving signal
may exist across it.
produces no further change in the resultant effect.
SLIP RINGS --Contacts that are mounted on
SCHEMATIC --A diagram that shows, by
the shaft of a motor or generator to which the
m e a n s of graphic symbols, the electrical
rotor windings are connected and against which
connections and functions of a specific circuit
the brushes ride. Devices for making electric
arrangement.
connections between stationary and rotating
contacts.
S E C O N D A R Y --The output coil of a
SOLENOID --An electromagnetic coil that
contains a movable plunger.
SELF-INDUCTION --The process by which
a circuit induces an EMF into itself by its own
SOLID-STATE DEVICE --An electronic
magnetic field.
device that operates by the movement of electrons
within a solid piece of semiconductor material.
SERIES CIRCUIT --An arrangement where
electrical devices are connected so that the total
current must flow through all the devices;
SOURCE --(1) The object that produces the
electrons have one path to travel from the negative
waves or disturbance. (2) The name given to the
terminal to the positive terminal.
end of a two-wire transmission line that is
connected to a source. (3) The device that
furnishes the electrical energy used by a
SERIES-WOUND --A motor or generator in
load.
which the armature is wired in series with the field
winding.
SPECIFIC GRAVITY --The ratio between
the density of a substance and that of pure water
SERVO --A device used to convert a small
at a given temperature.
movement into one of greater movement or force.
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