| AC
| Alternating current. |
| Adjustable Frequency Drive
| An electrical device used for controlling the speed of an AC motor. Also called AF Drive. |
| Bypass
| A device added to an AF drive which allows the motor power to be transferred via a set of contactors. This is useful in case of a drive failure, or if maintenance is being done on the drive. |
| Capacitor
| A device that consists of two conductors separated by an insulator. It is used to store electricity. |
| Displacement Power Factor
| The ratio of input KW to input KVA of the AF drive, excluding harmonics. |
| Filter
| A component for smoothing the DC current in an AF drive. |
| Frequency
| The number of cycles per second made by an alternating electrical current. The unit of measure is the Hertz. |
| Fundamental Frequency
| The frequency of line current. In North America, this is 60 Hertz. |
| Harmonics
| Certain frequencies; specifically, multiples of the fundamental frequency, at which unwanted and unusable voltages and currents are introduced into the system. |
| Horsepower
| Unit of measurement used for describing the amount of work a motor can do. |
| Impedance
| The apparent opposition to the flow of current though an AC electrical circuit; a force that literally impedes the flow of current. |
| Insulated Gate Bipolar Transistor
| A device used to switch the DC current in the inverter section of an AF drive. |
| Inverter
| The section of the AF drive which converts DC current into a “synthetic” AC current, which is then fed to the motor. |
| Line Reactor
| A device which adds impedance to the line to keep the impedance between the minimum and maximum allowed values for a particular piece of electric equipment, such as an AF drive. |
| Output Filter
| When the cable length for the application exceeds the acceptable length, adding this device to the circuit protects motor from voltage surges. Also called a DV/DT Filter. |
| Phase
| The relationship between the current and voltage in an AC circuit, with respect to their angular displacement. |
| Power Factor
| A blanket term, used to describe various measurements of the percentage of the input current available after passing through the system. See Total Power Factor, Displacement Power Factor. |
| Pulse Width Modulation
| A type of inverter which takes the DC current from the rectifier and switches it on and off very quickly, approximating a sine wave. |
| Rectifier
| A device which converts the incoming AC current to DC. |
| Remote Speed Control Signal
| This signal is used to control the speed of the drive remotely, from a control panel not located directly on the drive. |
| Synchronous Speed
| A motor’s design speed, determined by the number of poles that the motor has, and the frequency of the current being supplied to it. |
| Three-Phase
| A type of AC power where three AC currents are introduced at 120° variances. |
| Torque
| A measurement of rotational force. |
| Total Power Factor
| The ratio of the input KW to input KVA of the AF drive, including harmonics. |
| Voltage
| Electrical potential difference. The unit of measure is the Volt. |
| Voltage Transient
| Technical term for an unexpected and undesirable voltage surge in a circuit. |
