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AC motor
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A type of electric motor that runs on alternating current. AC motors are more commonly used in industry than DC motors but do not operate well at low speeds.
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alternating current
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Current that regularly reverses the direction of its flow in a repeating, cyclical pattern.
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armature
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The part of a motor or generator in which a current is induced by a magnetic field. The armature usually consists of a series of coils or groups of insulated conductors surrounding a core of iron.
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bearing
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A friction-reducing device that allows one moving part to glide past or rotate within another moving part.
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brush
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A device found inside a generator that is used only in pairs to transfer power from a rotating object. Brushes rest on the commutator of a DC motor.
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capacitor
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An electrical device that stores energy and releases it when needed. A capacitor gives a single-phase motor more torque but has a limited life.
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capacitor motor
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A single-phase motor with a running winding, starting winding, and a capacitor. Capacitor motors have more torque than other single-phase motors.
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capacitor start-and-run motor
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A type of capacitor motor that uses two capacitors, one for starting the motor, and one that remains in the circuit while the motor is running.
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capacitor-run motor
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A type of capacitor motor that has a capacitor and starting winding connected in series at all times.
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capacitor-start motor
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A single-phase motor with a capacitor. The capacitor gives the motor more starting torque.
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centrifugal switch
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A type of switch that operates using the centrifugal force created from the rotating shaft. The centrifugal switch activates and de-activates depending on the speed of the motor.
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direct current
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A current formed when electrons flow in one continuous direction.
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dual voltage motor
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A type of three-phase motor that operates on two voltage levels. Dual voltage motors allow the same motor to be used with two different power line voltages.
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efficiency losses
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A measure of the energy output versus the amount of input energy. The output energy is typically less than the input energy.
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electric motor
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A machine that converts electricity into mechanical energy or motion. An electric motor is a common power source for a mechanical system.
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electromagnetic induction
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The process in which current is induced in a magnetic field using a current-carrying coil. An AC generator produces a current through electromagnetic induction.
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endbell
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The cap at the end of the motor that houses the rotor bearing.
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field winding
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The conducting wire connected to the armature that energizes the pole pieces. Field windings are connected in series or parallel.
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generator
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A device that converts mechanical energy into electrical energy by magnetic induction.
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grounded
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Safely connected to a neutral body, like the earth, which can absorb a stray electrical charge.
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induction motor
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A type of AC motor that uses electrical current to induce rotation in the coils.
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magnet
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A device or object that attracts iron and produces a magnetic field.
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magnetic flux
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The area in and around a magnet that exhibits the powers of attraction and repulsion. Rotating an armature through lines of magnetic flux induces AC.
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motor nameplate
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A plate attached to a motor that displays all of the motor's information.
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output shaft
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The rotating part on the the AC motor that holds the rotor and allows it to turn.
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phase displacement
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The separation of the three phases in a three-phase motor. The windings are spaced 120° apart.
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reactance
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The resistance to the flow of alternating current due to inductance.
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resistance
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The opposition to current flow. Electricity flows in the path of least resistance.
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rotor
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The rotating part of a motor.
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running winding
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Heavy, insulated copper wire in a single-phase motor that receives the current for running the motor. The running winding remains connected when the starting winding is disconnected.
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secondary winding
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The second winding that current passes through in a transformer. The secondary winding contains fewer, but thicker wires that are wrapped into a coil.
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shaded-pole motor
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A single-phase motor that is 1/20 HP or less and is used in devices requiring low torque.
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sine wave
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The most common type of AC waveform. A sine wave consists of 360 electrical degrees and is produced by rotating machines.
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single voltage motor
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A type of three-phase motor that operates on only one voltage level. Single voltage motors are limited to having the same voltage as the power source.
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single-phase motor
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A type of motor with low horsepower that operates on 120 or 240 volts. Single-phase motors are often used in residential appliances like washing machines and air conditioners.
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slip
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The difference between a motor's synchronous speed and its speed at full load. Percent slip is a way to measure the speed performance of an induction motor.
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slip ring
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A conductive device attached to the end of a generator rotor that conducts current to the brushes. Slips rings are also used in AC wound rotor motors.
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split-phase motor
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A single-phase motor that consists of a running winding, starting winding, and centrifugal switch. The reactance difference in the windings creates separate phases, which produce the rotating magnetic field that starts the rotor.
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squirrel cage rotor
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A type of three-phase AC rotor that is constructed by connecting metal bars together at each end. It is the most common AC rotor type.
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starting winding
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Fine, insulated copper wire in a single-phase motor that receives current in the motor at startup. When the motor reaches 60-80% of th full load, the starting winding is disconnected and the running winding remains in the circuit.
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stator
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The stationary part of a motor.
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stepped down
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In electricity, a phrase used to describe voltage adjustment. To step down voltage means to decrease voltage.
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stepped up
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In electricity, a phrase used to describe voltage adjustment. To step up voltage means to increase voltage.
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synchronous motor
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A constant-speed AC motor that does not use induction to operate. A synchronous motor needs DC excitation to operate.
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thermal switch
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A type of switch often found in split-phase motors that signals that the motor may overheat.
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three-phase motor
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A motor with a continuous series of three overlapping AC cycles offset by 120 degrees. Three-phase power is used for all large AC motors and is the standard power supply that enters homes and factories.
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torque
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A force that produces rotation.
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transform
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To increase or decrease the voltage in a circuit.
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wound rotor
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A type of three phase rotor that contains windings and slip rings. This motor type permits control of rotor current by connecting external resistance in series with the rotor windings.
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