DC & AC rotating Machine
Short circuit
Circuit in which current takes a shortcut around the normal path of current flow
Rotor Frequency
The rate at which the stator magnetic field passes the poles in the rotor.
Gear ratio
The ration between the diameter of the drive gear and the driven gear.
A rotor
The rotating moving part of an alternator or generator, consisting of a core and windings, the convert torque to magnetic energy.
Short circuit open circuit ground fault
Typical types of circuit faults are
Bimetallic strip overload relay
can be designed to reset automatically.
4 poles
if the motor nameplate shows 1725 rpm as the full-load speed, the stator has how many poles?
Electrical lockout
refers to the process of locking the power source in the OFF position
Series Motor
A DC motor that has the field winding connected in series with the armature.
Compound motor
A DC motor with field connected in both series and shunt with the armature.
Narrow V-belt
A V-belt having a smaller cross section and higher profile than a standard belt that is designed for heavy-duty applications.
Flat belt
A belt that has a rectangular cross section and relies on friction for proper operation
Parallel soft foot
A condition that exists when one or two machine feet are higher than the others and parallel to the base plate.
one
In the split-phase motor, how many distinct electric-current phases exist in the stationary part of the motor when the rational speed of the motors shaft is between 90% and 95% of its rated full speed?
Circuit breaker
Is an overcorrect protection device with a mechanical mechanism that automatically opens a circuit when an overload condition or short circuit occurs.
Motor defect
an imperfection created during the manufacture of the motor that impairs its use.
Torque
compared to the simple, split-phase motor, the capacitor motor has a higher ________ at start up.
Angular misalignment
A condition where one shaft is at an angle to the other shaft.
Electronic overload relay
A device that has built-in circuitry to sense changes in current and temperature.
Shunt-wound generator
A generator that has its field windings connected as a shunt in parallel with the armature and the external circuit.
Bearing
A machine component used to reduce friction and maintain clearance between stationary and moving parts.
Motor - generator set
A motor and a generator with shafts connected used to produce the required DC power
Dual-voltage motor
A motor that operates at more than one voltage level.
Synchronous motor
A motor that rotates at exactly the same speed as the rotating magnetic field of the stator.
Stepper motor
A motor that uses discrete voltage and current pulses to control the movement of a load.
Polarized field frequency relay
A relay used to apply current to the DC field windings of a synchronous motor and to remove the discharge resistor from the starting circuit.
Tapered roller bearing
A roller bearing having tapered rollers
Ball bearing
A rolling-contact bearing that permits free motion between a moving part and a fixed part by means of balls confined between inner and outer rings.
Needle bearing
A rolling-contact roller type bearing with long rollers of small diameter.
Shading coil
A single turn of copper wire wrapped around part of the salient pole of a shaded-pole motor
Gear drive
A synchronous mechanical drive system that uses the meshing of two or more gears to transfer motion from one shaft to another.
Synchronous condenser
A synchronous motor operated at no load in order to provide power factor correction.
non compensated universal motor
A universal motor without extra windings added to the field poles.
Rotor stator
AC split-phase and capacitor motors are built with towo main sections. That section which consists of a shaft, a laminated and grooved core, and a squirrel cage-type "winding" is called the _______, while the section which consists of motor frame, laminated cored attached to the frame and field-type windings is called the _______
Linear induction motor
An AC motor that uses induction to create linear movement.
Revolving rotor alternator
An alternator where a fixed magnetic field is created in the stator, with the rotor turning within the stator, and AC power is supplied through the rotor slip rings and brushes.
Squirrel-cage rotor
An induction motor rotor consisting of conductors made from solid bars assembled into a cage frame resembling a squirrel cage.
Anchoring
Any means of fastening a mechanism securely to a use or foundation.
Interpoles
Are connected in series with the armature windings and are used to reduce sparking at the brushes of larger DC motors
Voltage unbalance Current unbalance voltage surges.
Common types of power problems in addition to single phase are:
The left-hand conductor rule
Explanation of the direction of a magnetic field around a conductor relative to the direction of the current in the conductor, where a left hand is used to illustrate the relationship.
30
Generally any voltage above _______ volts is considered dangerous.
Current Voltage
In a capacitive AC circuit the ______ reaches its peak value before the _____ peaks.
Synchronous speed of the motor
In a split-phase motor the speed of the rotating magnetic field (in the stationary part of the motor) is determined by the frequency of the AC input and by the number of poles in that stationary part of the motor. This speed is called the _______
90 degrees
In a split-phase motor, the phase difference between the current in the start winding and the current in the run winding is about 30 degrees. Putting a capacitor in series with the start winding makes this phase difference close to _________.
Voltage Current
In an inductive AC circuit the ____ reaches its peak value before the _______ peaks.
Fan blades
In many motor styles, the shorting rings contain ______ _____ that move the air through the motor for cooling.
Centrifugal switch
In most split-phase and capacitor motors, the start winding is de-energized when the motor reaches 75% to 85% of full speed. The _________ __________ is often used to disconnect the start winding before the motor reaches full-rated speed.
The speed rating of a motor
Is the approximate speed at which the rotor of a motor rotates when delivering rated power to a load.
True power
Is used by the resistive part of a circuit that performs the work and can be produced only when current and voltage are both positive or both negative.
Ferromagnetic material
Material that is easily magnetized and has high permeability.
Three-phase induction motors
Most common motors used in industrial applications because they operate for many years with little or no required maintenance.
Induction motors
Most split-phase capacitor motors have no commutator, nor other form of sliding contact to supply power to the rotating part of the machine. instead, the rotating section of the motor derives its current from its interaction with the trotting magnetic field of the motors stationary section. This characteristic puts the split-phase and capacitor motors in the class of electric motors known as
Overexcited synchronous motor
Operates at leading power factor, this is the normal operation condition of a synchronous motor.
Field Windings
Permanent magnets or ______ are used to produce the magnetic field in a DC motor.
Salient poles
Poles mounted onto a spider ring that is attached to the rotor shaft so that the entire assembly rotates.
Field windings
Stationary windings used to produce the magnetic field in an alternator or motor.
Microstepping
Stepper motor control that divides the standard stepper control pulse intervals into smaller intervals and sends modified current to the motor coils to increase the resolution of a stepper motor system.
Field Frame
That part of a DC motor which consists of a motor frame, laminated cores (or pole pieces) attached to the frame, and windings is called ________.
the Armature
That part of a DC motor which consists of a shaft, a laminated and grooved core, windings, and a commutator is called ______
Mutual induction
The ability of an inductor (coil) in one circuit to induce a voltage in another circuit or conductor.
Pull-up torque
The accelerating torque required to bring a load up to the correct speed.
Starting Torque
The advantage of a series-wound DC motor is its relatively high _______
Speed regulation
The advantage of a shunt-wound DC motor is relatively good __________.
The power rating
The amount of power a motor can deliver to a load.
Speed Regulation
The disadvantage of a series-wound DC motor is its relatively poor _________.
Armature reaction
The distortion of the magnetic fields that happens when a current-carrying wire is placed within a fixed magnetic field
Single phasing
The operation of a motor designed to operate on three phases operating on only two phases because on phase is lost.
A motors nameplate voltage rating
The optimal voltage that should be connected to the motor for the best operating performance.
Brush neutral
The position of the brushes where commutation can occur with minimal induced voltage in the armature coils.
Rotor
The rotating, moving part of a motor, consisting of a core and windings, which convert the rotating magnetic field of the stator into the torque that rotates the shaft.
Shaft
The rotor consists of a core and windings, which converts the rotating magnetic field of the stator into the torque that rotates the __________.
Reversing the start winding
The standard method used in industry for reversing the direction of rotation of a single phase motor.
wye or delta configuration
The stator in a single-voltage motor can be wired in ______
rotor core
The stator or __________ consist of many thin iron sheets laminated together, pressed into a frame, and secured in place.
Synchronous speed
The theoretical speed of a motor based on line frequency and the number of poles of the motor.
Run winding
There are two sets of windings in the stationary section of most split-space and capacitor motors. The main winding, which is always energized during the operation of the motor is called ______.
Adjustable-trip circuit breakers
Used in industry where equipment may be frequently changed and different overcorrect protection characteristics are required.
Megohmmeter
Used to measure insulation deterioration on various wires by measuring high resistance values during high-voltage test conditions.
Servomotor/ servo
Uses feedback signals to provide position and speed control.
plug fuses and cartridge fuses
What are the common fuses available?
Series wound motor
When a compound-wound DC motor loses its shunt field it becomes a ___________>
Brush neutral
When installing and adjusting brushes, the __________ must be sent in order to avoid excessive arcing, and other problems.
Brushes
Which part of the DC motor require the most maintenance attention ?
Eddy-current clutch
a clutch uses a magnetic field to couple a motor to a load.
dual-voltage motor
in a typical ______-______ _____, the run winding is split into two sections.
Permeability
is a measure of the ability of material to conduct magnetic flux
Motor Efficiency
is a measure of the effectiveness with which a motor converts electrical energy to mechanical energy.
The Service Factor rating
is a multiplier that represents the amount of load, beyond the rated load, that can be placed on a motor without causing damage.
Overload class rating
is an indicator of the maximum length of time it takes for the overload relay to trip at 600% overload.
Saturation
is the condition where a magnetic core has substantially all the magnetic domains aligned with the field and any increases in current no longer result in a stronger electromagnet.
Overload rating of an alternator
is the load above the normal load that can be carried for a specified period.
Decreases resistance
moisture
Axial load
or thrust load, is a load applied parallel to the rotating shaft.
Asynchronous
the difference between the speed of the shaft and the speed of the rotating magnetic field is called _______
Thermal expansion
the dimensional change in a substance due to a change in temperature.
Conventional current flow
the flow of positive charges from the positive terminal to the negative terminal of a power source.
Overcycling
the process of turning a motor ON and OFF more often than the motor design allows.
alignment
the process where the centerlines of two machine shafts are placed within specified tolerances.
Torque
typical measure in foot-pounds (ft-Ib), pound-feet (Ib-ft), and inch-ounces (in.-oz).
