Fan: In totally enclosed, fan cooled motor enclosures (TEFC), the cooling device used to keep the temperature rise below a specified value.
Fan Cover Guard: In totally enclosed, fan cooled motor enclosures (TEFC), the fan cover guard covers the fan assembly to keep out solid objects while allowing air to enter the fan chamber for cooling purposes.
Farad: A unit of measurement for electrical capacitance. A capacitor has a capacitance of one farad when a potential difference of one volt will charge it with one coulomb of electricity.
Fault Current: A current which results from the loss of insulation between conductors or between a conductor and ground.
FDE (From Drive End): A way to view the motor. From drive end refers to looking at the motor from the shaft end.
Feedback: As it generally relates to motors (gear-motors) and controls, feedback refers to the voltage information received by a feedback circuit. Depending on a pre-determined potentiometer setting, a motor control can correct the voltage to deliver appropriate speed and/or torque.
Ferromagnetic: A material with high magnetic permeability (imposes little resistance to orientation in the presence of a magnetic field). Such materials as iron, steel, and nickel are ferromagnetic substances.
Field: A term commonly used to describe the stationary (stator) member of a D.C. motor. The field provides the magnetic field with which the mechanically rotating (armature) member interacts.
Field Control: Method of controlling DC motor speed by varying the field current in the shunt field windings.
Field Economy: A circuit design feature of a DC motor shunt field supply that reduces the supply voltage output after a predetermined period of time. On may field supplies, this means 50% reduction in output voltage 2 to 3 minutes after machine shutdown (idle). A field economy circuit serves to reduce standby power consumption and prolong the insulation life of the motor field windings.
Field Forcing: Temporarily over-exciting a motor shunt field to overcome the L/R time constant, increase the rate of flux change and rapidly reverse the direction of shunt motor field current.
Field Range: The range of motor speed from base speed to the maximum rated speed.
Field Reversing: One method for producing regeneration. It is accomplished by changing the direction of current through the motor field, which reverses the polarity of the motor CEMF to account for generator action.
Field Weakening: The introduction of resistance in series with the shunt wound field of a motor to reduce the voltage and current which weakens the strength of the magnetic filed and thereby increase the motor speed.
Filter: A device that passes a signal or a range of signals and eliminates all others.
Flux: The magnetic field which is established around an energized conductor or permanent magnet. The field is represented by flux lines creating a flux pattern between opposite poles. The density of the flux lines is a measure of the strength of the magnetic field.
FODE (From Opposite Drive End): A way to view the motor. From opposite drive end refers to looking at the motor from opposite the shaft end.
Follower Drive: A drive in which the referenced input and operation are direct functions of another drive, called the master drive.
Four-Quadrant Operation: The four combinations of forward and reverse rotation and forward and reverse torque of which a regenerative drive is capable:
Force: The tendency to change the motion or position of an object with a push or pull. Force is measured in ounces or pounds.
Form Factor: A figure of merit which indicates how much rectified current departs from pure (non-pulsating) D.C. A large departure from unity form factor (pure D.C.) increases the heating effect of the motor and reduces brush life. Mathematically form factor is the ratio of the root-mean-square (rms) value of the current to the average (av) current of Irms/Iav.
Form Wound Coils: Coils wound in form and shaped ready to insert into the slot of a motor.
Fractional Horsepower Motor: A motor with a continuous rating of less than one horsepower.
Frame: The main motor housing. Can be constructed of aluminum, steel, or cast iron.
Frame Size: The physical size of a motor, usually consisting of NEMA defined "D" and "F" dimensions at a minimum. The "D" dimension is the distance in quarter inches from the center of the motor shaft to the bottom of the mounting feet. The "F" dimension relates to the distance between the centers of the mounting feet holes.
Frequency: The rate at which alternating current reverses its direction of flow. Measured in hertz (Hz); 1 Hz = 1 cycle per second.
Full Load Current: The current drawn from the line when the motor is operating at full load torque and full load speed at rated frequency and voltage.
Full Load Speed: The speed that the output shaft of the drive motor attains with rated load connected and with the drive's controller adjusted to deliver rated output at rated speed.
Full Load Torque: The full-load torque of a motor is the torque necessary to produce its rated horsepower at full-load speed in pounds at a 1-foot radius, it is equal to the horsepower times 5252 divided by the full-load speed.
Full Pitch: The full pitch value is obtained by dividing the number of slots by the number of poles.
Full Wave Rectification: Full wave rectification passes the positive half and inverts the negative half cycle of the input sinusoid so that the output contains two half sine pulses for each input cycle.
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