experiments with motors

7/26/2019 Experiments With Motors

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Experiments with motors

Motors

Electric motors are used to efficiently convert electrical energy into mechanical

energy. Magnetism is the basis of their principles of operation. They use

permanent magnets, electromagnets, and exploit the magnetic properties of

materials in order to create these amazing machines.

There are several types of electric motors available today. The following

outline gives an overview of several popular ones. There are two main classes

of motors: A and !. A motors re"uire an alternating current or voltage

source #li$e the power coming out of the wall outlets in your house% to ma$e

them wor$. ! motors re"uire a direct current or voltage source #li$e the

voltage coming out of batteries% to ma$e them wor$. &niversal motors can

wor$ on either type of power. 'ot only is the construction of the motors

different, but the means used to control the speed and tor"ue created by each of

these motors also varies, although the principles of power conversion are

common to both.

Motors are used (ust about everywhere.

)n your house, there is a motor in your furnace for the blower, for the inta$e air,

in the sump well, dehumidifier, in the $itchen in the exhaust hood above the

stove, microwave fan, refrigerator compressor and cooling fan, can opener,

garbage disposer, dish washer pump, cloc$s, computer fans, ceiling fans, and

many more items* ) once counted over +- electric motors in my house.

)n industry, motors are used to move, lift, rotate, accelerate, bra$e, lower andspin material in order to coat, paint, punch, plate, ma$e or form steel, film,

paper, tissue, aluminum, plastic and other raw materials.

They range in power ratings from less than ++// hp to over +//,/// hp. The

rotate as slowly as /.//+ rpm to over +//,/// rpm. They range in physical size

from as small as the head of a pin to the size of a locomotive engine.
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What happens when a wire carrying current is within a

magnetic field?

This is the Left Hand Rulefor motors.

The first finger points in the direction of the magnetic field #first 0 field%,

which goes from the 'orth pole to the 1outh pole.

The second finger points in the direction of the current in the wire #second 0

current%. The thumb then points in the direction the wire is thrust or pushed while in

the magnetic field #thumb 0 tor"ue or thrust%.

1o, when a wire carrying current sits perpendicular to a magnetic field, a force

is created on the wire causing it to move perpendicular to the field and direction

of current. The greater the current in the wire, or the greater the magnetic field,

the faster the wire moves because of the greater force created. )f the wire sits

parallel with the magnetic field, there will be no force on the wire.

This is what Tesla exploited to ma$e A motors.

Experiment

2et3s chec$ this out by placing a magnet near an oscilloscope and see what

happens. 4emember, the trace of electrons on the scope goes from left to right,

which means that conventional current is going from right to left #conventional

current is opposite to the electron current%. 1o, rotate your hand so that the

current is going in the opposite direction in the wire from what is shown in the

photo above, from right to left. Then, if ) place a 'orth pole near that trace of

electrons, the field is going into the scope face, same direction as shown in thephoto above. Therefore, the thrust will be down, since the thumb is then

pointing down. A 1outh pole would cause the trace to move in the opposite

direction 5 up.

2et3s see what we get.


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The first photo is the scope trace with no magnetic field.

The second photo is the scope trace with a 'orth pole near it. The trace goes

down li$e we expected from the paragraph above.The third photo is the scope trace with a 1outh pole near it. The trace goes up

li$e we expected.

The fourth photo is the scope trace with a 1outh pole on the left, causing the

trace to move up, and a 'orth pole on the right, causing the trace to move

down.

ool* Experiment matches theory*

This force on the electrons is what causes the wire carrying current in a

magnetic field to want to move, which is what causes motors to rotate.

Fleming's Left Hand Rule Demo

This demo shows what happens to a current carrying wire sitting in a magnetic field,supporting the 6leming 2eft 7and 4ule. There are two large donut magnets attached to

the steel brac$ets, bolted to the wood base. A cradle or swing made out of bare copper

wire is hung between the two wire supports. The power is supplied by a +8.9actransformer, which is rectified and limited by four +;hm resistors. The switch is a

momentary switch to the left and to the right, with center position off.


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This first photo shows the swing with no current flowing. The second photo shows theswing moved forward due to the current flowing from right to left in the wire. The third

photo shows the swing moved toward the bac$ due to the current flowing from left to

right in the wire. This is reaction is used in motors and in spea$ers.

ypes of Motors

There are several types of motors used in industrial, commercial and residential

applications:
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For more information! go to"

D# motors

&niversal

$# motors

2inear

'ot only are the motors built differently, but their speed tor"ue curves and

load regulation curves are different from each other. This is a case of

optimizinga machine for specific characteristics.

Another area of study is the control of each of these motors. The type of power

electronics and control electronics needed to control the speed, tor"ue and

direction of rotation of each type of motor is uni"ue for each one. A motor

controller is often referred to as a drive. The hundreds of papers presented

every year at the )ndustrial Applications 1ocietyof the )EEEis an indication ofthe amount of time spent improving the control of motors. !rives reduce the

energy used by motors in fan and pump applications, and improve processes in

thousand of other applications. This is a fascinating area of study and an

exciting profession* #)t also (ust happens to be my profession, too*%

Search
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