generators

On a generator waveform what does the vertical axis mean? The horizontal axis?

(Y)=voltage (X)=Time

What are 2 types of AC electric motors?

1. Synchronous Motor 2. Induction Motor

What are the 2 different ways that a generator can work?

1.By moving a conductor (coil) through a stationary magnetic field across or perpendicular to the magnetic field lines 2.by a stationary coil in a moving/changing magnetic field. The coil is rotated by a source of mechanical energy and the mechanical energy of rotation is converted to electrical energy.

What is the construction of a DC generator

1.milar construction of the AC generator includes one coil a commutator ring (single split ring) is used in place of the set of slip rings 2.eds the generated current to the external circuit 3.keeps current flowing in one/same direction 4.it acts like a switch-changing the polarity of the contact on the loops of wire at precisely those points when the current flow through the loop would reverse

How many alterations per second and what cycle current does a AC generator use

120 alternations per second with a 60 cycle current

What is a generator?

A device that converts mechanical energy of motion (input) into electrical energy (output).

What are the types of generators?

AC, DC, single phase, three phase, hi frequency

How does the AC generator work?

As the coil rotates in a magnetic field, the magnitude and directrion of the induced current chages. The induced current varies and alternates, rises to a maximum, drops to zero, then increases to a maximum in the opposite direction. Going from one direction and then to the other produces AC power.

What are synchronous motors useful in

timing mechanisms

Rapid change in magnitude and direction of the current causes correspoinding fluctuation in stregnth and direction of magnetic field set up around a coil in a circuit

Bucking

Hindrance of flow to current as a result of adding a capacitor to the AC circuit

Capacitive Reactance

what periodically reverses polarity as the current reverses?

Capacitor in an AC

What offers a certain amound of hindrance to the flow of current known as capacitive reactance

Capacitor which directly periodically reverses polarity as the current reverses

converts electric energy provided by an electric current into mechanical energy of motion

DC Motor

What types of electric motors are there?

DC Motor AC Motor

what is the configuration for a DC electric motor and an AC electric motor

DC motor has commutator rings (instead of slip rings in the AC Gen.) AC has slip rings

Explain AC generator waveform

Each cycle consists of 2 alternations. Starts at 0, raches a mx in one direction (above X axis), returns to 0 & increases to a max in the opposite direction (below the x axis) & finally returns to 0

How does a DC motor work

Electric current from power supply is sent through the wire coils, as current flow through a force is exerted on the coils as a resultof the interactions of the two magnetic fields. the force that causes the coil to rotate provides the push in one clockwise direction through only half of a revolution of the coil, the direction of the force exerted on the coil reverse however, during the second half of the turn of the coil as a result of the coil's new orientation within the magnetic field of the magnet. to prevent this the direction of current flow in the coil must be reversed during the second half of the rotation by a commutator

How do we know the direction of the Induced current of an AC motor.

Fleming's Left Hand Motor rule

For the direction of induced current what do we use? What shows what is moving in what direction?

Fleming's Right Hand Generator Rule Thumb=direction of the conductor Index Finger=direction of the magnetic field Middle Finge=direction of the current

total resistance of an AC current

Impedance

Opposition to a change in the amount of current flowing

Inductance

A very powerful motor

Induction Motor

has a stator with an even number of stationary electromagnets distributed around the periphery

Induction Motor

Whyat are some advantages of AC

Needed for operation of transformers (rad equip) AC uses low amps (10) and high voltage (5000) to reduce power loss since electric current generated at power plants must travel long distances

For the AC motor we use Fleming's left hand motor rule, how do we know what is going in what direction?

Pointer finger=direction of the magnetic field middle finger=direction of induced current in a conductor thumb=direction that thrust or motion will move

What are inducton motors used for with X-Ray tubes

Powering the rotating anode of the x-ray tube

What is the DC generator waveform referred to as

Pulsating direct current (different from steady DC supplied by a battery

Device that converts electrical energy to mechanical energy? What are its components similar to?

The electric motor-it has similar components to a generator

a result of the interaction of magnetic fields when an electric current is sent along a conductor that is residing in a magnetic field

The motor principle

what is the frequence of AC

The number of cycles/second

What is a DC motor

The reverse of a direct current generator. converts electric energy (input)provided by an electric current into mechanical energy (output) of motion

Whenever a conductor carrying a current is placed in a magnetic field what happens?

There is a force exerted on the conductor (directly proportional to legnth or number of turns, stregnth of magnetic field, and size of current)

How does a generator work?

Through process of electromagnetic induction

What are the conditions that an electric motor must have

a conductor must be located in an external magnetic field and must be carrying current

What are generators also called?

a dynamo

What is an advantage of a synchronous motor

a fixed speed may be useful in certain types of equipment such as electric clocks

What is a stator supplied by

a multiphase (out of step) current

current flow in a coil is reversed every half rotation as this makes contact with the brushes of reversed polarity thus assuring that the force applied to the coil always acts in the same direction to produce continuous rotation

commutator

What is the armature of an electric motor supplied with

current

For an AC generator what does 120 alternations per second with a 60 cycle current mean?

current changes directions in the conductor 120 times/second.

A coil continues to rotate as long as it has what

current flow is maintained through it

How is current fed in a synchronous motor and what does it cause

current is fed to the armature causing it to rotate in the magnetic field

Where is the rotor located

in the center of the induction motor

What is the bucking tendancy of inductance called? What is it measured in and why?

inductive reactance and is measured in Ohms because it opposes the flow of current

What is the main disadvantage of a synchronous motor

limited speeds of operation, it must be in step with the generator

what does the Induction motor not have? What does it have instead

no slip rings or commutators or brushes it consistso f a stator and a rotor

The distnce from 2 successive points on a curve represents What?

one cycle of AC (US uses 60 cycle AC)

What is the basic design of an AC motor

same as the DC motor except: uses slip rings (instead of brushes or a commutator)since the current flow naturally reverses its direction of flow 120 times/sec

outer stationary portion of motor with coils of wire around a ferromagnetic core which forms even numbers of stationary electromagnetics

stator

an alternating current AC motor which operates at a fixed ________ speed proportional to the frequency of the applied ac power

synchronous motor

a synchronous motor must be synchronous with the speed of the AC generator, how does the happen

the arature must rotate at the same speed or number of rpm as the frequency of the current (60 cycles AC)being suppplied by the generator or some fixed multiple of that speed (1/30 sec; 1/20sec; 1/15 sec)

What does Impedance depend on?

the inductive reactance, capacitive reactance and true electrical resistance

What does the motor effect result from in an electric motor

the interaction between the magnetic field around the electron current in the conductor and the other magnetic field.

How does bucking happen because of a coil's inductance?

the persistently changing magnetic field around coil supplied by an AC sets up a back electromotive force in a direction opposite the applied alternating voltage, first in one direction and then in the other.

What is in the center of an induction motor

the rotating part or rotor, consisting of bars of copper arranged around a cylindrical iron core, and resembling a squirrel cage

For an AC generator when is no current induced?

when the wire is moving parallel to the magnetic field