DC & AC rotating Machine

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.

plug fuses and cartridge fuses

What are the common fuses available?

Circuit breaker

Is an overcorrect protection device with a mechanical mechanism that automatically opens a circuit when an overload condition or short circuit occurs.

Adjustable-trip circuit breakers

Used in industry where equipment may be frequently changed and different overcorrect protection characteristics are required.

Overload class rating

is an indicator of the maximum length of time it takes for the overload relay to trip at 600% overload.

Bimetallic strip overload relay

can be designed to reset automatically.

Electronic overload relay

A device that has built-in circuitry to sense changes in current and temperature.

Ferromagnetic material

Material that is easily magnetized and has high permeability.

Conventional current flow

the flow of positive charges from the positive terminal to the negative terminal of a power source.

Mutual induction

The ability of an inductor (coil) in one circuit to induce a voltage in another circuit or conductor.

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.

A motors nameplate voltage rating

The optimal voltage that should be connected to the motor for the best operating performance.

The power rating

The amount of power a motor can deliver to a load.

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.

Decreases resistance

moisture

Electrical lockout

refers to the process of locking the power source in the OFF position

Permeability

is a measure of the ability of material to conduct magnetic flux

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.

30

Generally any voltage above _______ volts is considered dangerous.

Field Windings

Permanent magnets or ______ are used to produce the magnetic field in a DC motor.

Interpoles

Are connected in series with the armature windings and are used to reduce sparking at the brushes of larger DC motors

Starting Torque

The advantage of a series-wound DC motor is its relatively high _______

Speed Regulation

The disadvantage of a series-wound DC motor is its relatively poor _________.

Series wound motor

When a compound-wound DC motor loses its shunt field it becomes a ___________>

Armature reaction

The distortion of the magnetic fields that happens when a current-carrying wire is placed within a fixed magnetic field

Brush neutral

The position of the brushes where commutation can occur with minimal induced voltage in the armature coils.

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.

Shunt-wound generator

A generator that has its field windings connected as a shunt in parallel with the armature and the external circuit.

the Armature

That part of a DC motor which consists of a shaft, a laminated and grooved core, windings, and a commutator is called ______

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 ________.

Speed regulation

The advantage of a shunt-wound DC motor is relatively good __________.

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.

Squirrel-cage rotor

An induction motor rotor consisting of conductors made from solid bars assembled into a cage frame resembling a squirrel cage.

Fan blades

In many motor styles, the shorting rings contain ______ _____ that move the air through the motor for cooling.

Shaft

The rotor consists of a core and windings, which converts the rotating magnetic field of the stator into the torque that rotates the __________.

Synchronous speed

The theoretical speed of a motor based on line frequency and the number of poles of the motor.

Rotor Frequency

The rate at which the stator magnetic field passes the poles in the rotor.

wye or delta configuration

The stator in a single-voltage motor can be wired in ______

Dual-voltage motor

A motor that operates at more than one voltage level.

Torque

typical measure in foot-pounds (ft-Ib), pound-feet (Ib-ft), and inch-ounces (in.-oz).

Pull-up torque

The accelerating torque required to bring a load up to the correct speed.

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.

rotor core

The stator or __________ consist of many thin iron sheets laminated together, pressed into a frame, and secured in place.

Anchoring

Any means of fastening a mechanism securely to a use or foundation.

Angular misalignment

A condition where one shaft is at an angle to the other shaft.

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.

Gear drive

A synchronous mechanical drive system that uses the meshing of two or more gears to transfer motion from one shaft to another.

Gear ratio

The ration between the diameter of the drive gear and the driven gear.

Eddy-current clutch

a clutch uses a magnetic field to couple a motor to a load.

Flat belt

A belt that has a rectangular cross section and relies on friction for proper operation

alignment

the process where the centerlines of two machine shafts are placed within specified tolerances.

Thermal expansion

the dimensional change in a substance due to a change in temperature.

Bearing

A machine component used to reduce friction and maintain clearance between stationary and moving parts.

Parallel soft foot

A condition that exists when one or two machine feet are higher than the others and parallel to the base plate.

Axial load

or thrust load, is a load applied parallel to the rotating shaft.

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.

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 _______

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 ______.

Voltage

Current

In an inductive AC circuit the ____ reaches its peak value before the _______ peaks.

Current

Voltage

In a capacitive AC circuit the ______ reaches its peak value before the _____ peaks.

Torque

compared to the simple, split-phase motor, the capacitor motor has a higher ________ at start up.

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.

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

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?

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 _______

Asynchronous

the difference between the speed of the shaft and the speed of the rotating magnetic field is called _______

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 _________.

4 poles

if the motor nameplate shows 1725 rpm as the full-load speed, the stator has how many poles?

Reversing the start winding

The standard method used in industry for reversing the direction of rotation of a single phase motor.

Shading coil

A single turn of copper wire wrapped around part of the salient pole of a shaded-pole motor

dual-voltage motor

in a typical ______-______ _____, the run winding is split into two sections.

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.

Linear induction motor

An AC motor that uses induction to create linear movement.

non compensated universal motor

A universal motor without extra windings added to the field poles.

Stepper motor

A motor that uses discrete voltage and current pulses to control the movement of a load.

Servomotor/ servo

Uses feedback signals to provide position and speed control.

Salient poles

Poles mounted onto a spider ring that is attached to the rotor shaft so that the entire assembly rotates.

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.

Field windings

Stationary windings used to produce the magnetic field in an alternator or motor.

Overload rating of an alternator

is the load above the normal load that can be carried for a specified period.

A rotor

The rotating moving part of an alternator or generator, consisting of a core and windings, the convert torque to magnetic energy.

Synchronous motor

A motor that rotates at exactly the same speed as the rotating magnetic field of the stator.

Motor - generator set

A motor and a generator with shafts connected used to produce the required DC power

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.

Synchronous condenser

A synchronous motor operated at no load in order to provide power factor correction.

Overexcited synchronous motor

Operates at leading power factor, this is the normal operation condition of a synchronous motor.

Single phasing

The operation of a motor designed to operate on three phases operating on only two phases because on phase is lost.

Brush neutral

When installing and adjusting brushes, the __________ must be sent in order to avoid excessive arcing, and other problems.

Voltage unbalance

Current unbalance

voltage surges.

Common types of power problems in addition to single phase are:

Overcycling

the process of turning a motor ON and OFF more often than the motor design allows.

Motor defect

an imperfection created during the manufacture of the motor that impairs its use.

Short circuit

open circuit

ground fault

Typical types of circuit faults are

Short circuit

Circuit in which current takes a shortcut around the normal path of current flow

Three-phase induction motors

Most common motors used in industrial applications because they operate for many years with little or no required maintenance.

Megohmmeter

Used to measure insulation deterioration on various wires by measuring high resistance values during high-voltage test conditions.

Brushes

Which part of the DC motor require the most maintenance attention ?