Appendix D: Terms and Definitions

AC Contactor: Designed for the specific purpose of establish or interrupting an AC power circuit. A contactor is a high power, electromagnetic switch. It is constructed of a low voltage "control circuit" (for example, 24VDC) and a "power circuit," where the high voltage is being controlled (for example 460VAC, 3-Phase). A contactor is essentially a high power relay.
AC Drive: An electronic device that converts a fixed frequency and voltage source to an adjustable frequency and AC voltage source. It controls the speed, torque, horsepower, and direction of an AC motor.
A/D Converter: A device that converts an analog signal (continuous values of voltage or current, e.g., sinewave) to a digital number.
Adjustable Speed: Varying the speed of a motor, either manually or automatically. The desired operating speed (set speed) is relatively constant regardless of load.
Adjustable Speed Drive (Electrical): An adjustable-speed drive consists of the motor, drive controller, and operator's controls (either manual or automatic).
Analog Input (AI): An analog input is an input for the user-supplied DC signal. The signal may be a speed reference or a process feedback. This signal can be from manual speed pot DC voltage (0 to 10 VDC) DC current (0 to 20 mADC). For many drives, the abbreviation is AI.
Analog Input Module: An I/O module that converts an analog signal from an analog measuring device that may be processed by the processor.
Analog Output Module: An I/O module that converts a digital signal from the processor into an analog output...

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