| Adjustable Frequency Drive
| This device converts the incoming 60 Hz power into any desired frequency, allowing an AC motor to run at virtually any speed. |
| Armature
| The turning conductor in a DC motor. |
| Base Speed
| The speed at which a DC motor will run with full voltage applied to the armature and the field. |
| Brushes
| The stationary components of the commutator, providing current to the rotating commutator segments. |
| Coils
| The stationary windings of the DC motor that generate an electromagnetic field. |
| Commutator
| A device used in a DC motor to reverse the current in the armature every one-half rotation so that the magnetic fields will work together to maintain rotation. |
| Compound Motor
| A DC motor that combines the characteristics of both the series and the shunt motors. |
| Conventional Flow Theory
| A theory regarding the flow of current. It states that current flows from positive to negative. |
| DC Injection Braking
| A method of braking an AC motor in which direct current (DC) is applied to the stationary windings of an AC motor after the AC voltage is removed. |
| Delta
| A motor connection arrangement where each winding is wired end to end to form a completely closed loop circuit. |
| Dual Voltage Motor
| A motor made for two voltages. It enables the same motor to be used with two different power line voltages. |
| Dynamic Braking
| A method of braking a DC motor by reconnecting a running motor to act as a generator immediately after it is turned off. Reconnecting the motor in this way makes the motor act as a loaded generator that develops a retarding torque, rapidly slowing the motor. |
| Electron Flow Theory
| A theory regarding the flow of current which states that current flows from negative to positive. |
| Full Load Speed
| The true speed at which a motor turns, found on the nameplate. To calculate, take Synchronous Speed minus Percent Slip. It is the speed of the rotor. |
| Horsepower
| A unit of power measurement, used for rating the amount of Work a motor can do. One horsepower equals 33,000 foot-pounds per minute of Work. |
| Induction
| The process of producing a current by the relative motion of a magnetic field across a conductor. |
| Left Hand Flux Rule
| The relationship of the factors used to determine is which direction the magnetic flux moves around a conductor. Imagine grasping the wire with your left hand, making sure your thumb points in the direction of the current flow. Your fingers will curl around the wire in the direction of the magnetic flux. |
| Magnetic Flux
| The direction of a magnetic field. |
| Magnetically Reversing Starter
| A device that performs the same function as a manual reversing starter. Electrically, the only difference between manual and magnetic starters is the addition of forward and reversing coils and the use of auxiliary contacts. |
| Manual Reversing Starter
| A device used to change the direction of rotation of a three-phase, a single-phase or a DC motor. It is made by simply connecting two manual starters together. |
| Neutral Position
| The position at which the armature in a DC motor is parallel to the magnetic field, where no torque is produced. |
| Percent Slip
| The percentage difference between a motor’s Synchronous Speed and its Full Load Speed. |
| Polarity
| Direction of current flow through a conductor. |
| Poles
| The stationary windings of the DC motor that generate an electromagnetic field. |
| Power
| A measure of work done per unit of time. |
| Reduced Voltage Starter
| A type of starter that ramps up the power to a motor gradually to cut down on current draw at start-up. |
| Right Hand Motor Rule
| The relationship between the factors involved in determining the movement of a conductor in a magnetic filed. The index finger points in the direction of the magnetic field (N to S), the middle finger points in the direction of electron current flow in the conductor, and the thumb points in the direction of the force on the conductor. |
| Rotor
| The rotating part of an AC motor. |
| Series Motor
| A DC motor with the field coil wired in series with the armature coil. It is also called a universal motor. |
| Shunt Motor
| A DC motor with the field coil wired in parallel with the armature coil. |
| Starter
| A device that is used to start a motor from a stop. |
| Stationary Windings
| The stationary windings of the DC motor that generate an electromagnetic field. |
| Stator
| The stationary part of an AC motor. |
| Squirrel Cage Induction Motor
| The most common AC motor type, named for the rotor’s resemblance to a cage used for exercising squirrels. |
| Synchronous Speed
| The rotational speed of the stator, defined by the formula:
N = 120f/P
Where:N = the synchronous speed of the motor in revolutions per minute (RPM)f = the frequency supplied to the motor in Hertz (Hz)P = the number of poles the motor has |
| Torque
| Turning or rotational force. |
| Work
| Applying a force over a distance. |
| Wye
| A motor connection arrangement where one end of each of the three-phases is connected to the other phases internally. The remaining end of each phase is then brought out externally. |
