GE Industrial Solutions AF-300E$ - Manual (Page 127)

11-6
Synchronous Speed: The speed of an AC induction motor’s
rotating magnetic field. It is determined by the frequency
applied to the stator and the number of magnetic poles
present in each phase of the stator windings. Mathemati-
cally, it is expressed as: Sync Speed (RPM) = 120 X Ap-
plied Freq. (Hz)/Number of poles per phase.
Tachometer - Generator (Tach): A small generator normally
used as a rotational speed sensing device. Tachometers
are typically, coupled to the shaft of DC or AC motor requir-
ing close speed regulation. The tach feeds a signal to a
controller which then adjusts the output voltage or frequency
to the motor. This feedback signal can be either an analog
DC signal (V/RPM) or digital (pulses/Revolution).
Thread Speed: A fixed low speed, usually adjustable, sup-
plied to provide a convenient method for loading and thread-
ing machines. May also be called a preset speed.
Torque: A turning force applied to a shaft, tending to cause
rotation. Torque is normally measured in ounce-inches or
pound-feet and is equal to the force applied, times the ra-
dius through which it acts.
Torque Constant (in-lbs): This motor parameter provides a
relationship between input current and output torque. For
each ampere of current applied to the rotor, a fixed amount
of torque will result.
Torque Control: A method of using current limit circuitry to
regulate torque instead of speed.
Transducer: A device that converts one energy form to an-
other (e.g. mechanical to electrical). Also, a device that
when actuated by signals from one or more systems or
media can supply related signals to one or more other sys-
tems or media.
Transient: A momentary deviation in an electrical or mechani-
cal system.
Transistor: A solid-state three-terminal device that allows
amplification of signals and can be used for switching and
control. The terminals are called the emitter, base and col-
lector.
Vector: A quantity that has magnitude, direction and sense.
This quantity is commonly represented by a directed line
segment whose length represents the magnitude and worse
orientation in space represents the direction.
VVI: A type of AC adjustable frequency drive that controls
the voltage and frequency of the motor to produce variable
speed operation. A VVI type drive controls the voltage in a
section other than the output section where frequency gen-
eration takes place. The frequency control is accomplished
by an output bridge circuit which switches the variable volt-
age to the motor at the desired frequency.
X-Axis: The axis of motion that is always horizontal and
parallel to the work holding surface.
Y-Axis: The axis of motion that is perpendicular to both the
X and Z axes.
Z-Axis: The axis of motion that is always parallel to the prin-
cipal spindle of the machine.