ELECTRICAL DICTIONARY OF PARTS, UNITS AND TERMS
Before taking up the study of automobile ignition systems and
electrical appliances, we will first devote a little time to study,
in order to become familiar with the different electrical parts,
functions, terms and names applied to the various units, and machines.
In the first place electricity is not a juice or fluid that flows
through a wire, but is a generated electro-motive force that may be
held in storage or conducted from one place to another. It will not
flow without a round circuit and seeks ground return at the slightest
opportunity. It is designated in terms which express quality, quantity,
force and action.
=Voltage.=--A volt is an electrical unit, expressing the force or
pressure of the current. The voltage of a system simply means the
difference of pressure exerted on the system measured in volts.
=Ampere.=--An ampere is an electrical unit expressing the quality or
intensity of the current.
=Ohm.=--An ohm is an electrical unit expressing resistance; or the
resistance of conductors to the flow of current.
=Current.=--The current is the generated electro-motive force.
=Circuit.=--Electricity will not flow unless there is a circuit or
ground return to its original source.
=Low Tension Current.=--Low tension current is generated in the primary
winding or coil by placing it in a magnetic field. It will flow from
one point to another but has very little strength and will not jump
the gap at the spark plug. It is used for lighting purposes, or
conducted to an induction coil which transforms it into a high tension
alternating current.
=High Tension Current.=--High tension current is generated in the
secondary coil by interruption of the primary current or by the rapid
magnetization and demagnetization of the core and primary coil.
=Direct Current.=--Direct current is produced by placing a coil or wire
in a magnetic field. It is usually conducted to an induction coil where
it is transformed into a high tension alternating current.
=Alternating Currents.=--Alternating currents are produced by the rapid
breaking down and building up of the primary current. An alternating
current flows forward from zero to its highest point of strength and
back again to zero. The alternating action takes place so rapidly that
a light can be connected in this circuit and it will burn steadily
without any noticeable fluctuation.
[Illustration: Fig. 54. Coil Diagram]
=Induction Coil.=--An induction coil consists of a soft iron core;
a primary and secondary winding, and a set of platinum points. The
primary winding is wound directly over the core and consists of a few
turns of thick wire. The secondary wire is wound over the primary
and consists of a great many turns of thin wire. Fig. 54 shows the
functional action of an induction coil. Both of the coils are wound
on the soft iron core A-B. The primary current which is supplied in
this case by a cell or number of cells, C and D, is broken at frequent
intervals of time. The method of doing this is as follows: One terminal
of the primary coil is connected to the fixed platinum stud D, the
other terminal to a spring which carries a piece of soft iron, E. When
the spring is unbent it touches the stud D, and a current passes in
the primary. The core of soft iron becomes magnetized and attracts the
soft iron disc, E, thus breaking contact at D. The current is stopped
and the core immediately becomes unmagnetized, the spring flies back
and the contact is again made. The process is then repeated. When the
contact in the primary is broken the current flows in one direction in
the secondary coil, when it is made the current flows in the opposite
direction in the secondary. Thus an alternating current is set up in
the secondary current of great frequency.
=Commutator.=--The commutator or timer as it is commonly called is used
only in connection with the induction coil to complete the circuit when
a spark is required at the plug in the cylinder.
=Insulation.=--Insulating is the act of covering a conductor with a
non-conducting substance to prevent the spark from jumping or seeking
ground.
=Choking Coil.=--A choking coil in simple form consists of a coil and
iron core to increase self-induction. It is used to reduce currents of
high pressure and is commonly called a bucking coil.
=Fuse.=--A fuse is used to prevent conductors or coils from being
damaged by heat generated from high pressure currents. It consists of a
metal and glass tube which contains a fine wire. This wire being much
thinner than the wire of the cable, the heat naturally develops faster
at this point, and is soon high enough to melt the wire and break or
open the circuit, and thus any further damage to the insulation is
prevented.
=Condenser.=--A condenser usually consists of a few strips of folded
tin foil insulated from each other with paraffined or oiled paper. It
absorbs, restricts and distributes high pressure currents and also
prevents excessive sparking at the contact points.
[Illustration: Fig. 55. Dynamo--Diagram of Action]
=Dynamo.=--A dynamo is a machine which converts mechanical energy
into electric energy, and must consist of at least two separate parts;
the field magnets to create the magnetic field, and the armature or
conductor in which the current is generated. One or the other of these
must be in motion in order to cut the lines of magnetic force crossing
the field. Fig. 55 shows the operation of the most common or simplest
type of alternating current producing machine, which is similar and
conforms in action to the high tension magneto and generator. Field
pieces magnetize the pole pieces N and S. A wire coil is placed in
the field at right angles to the magnetic lines of force turned to
the right. It takes up the position of the dotted lines and no lines
of force are cut, whereas in its original position, as many lines of
force as possible are cut. Turning the coil on its axles, a-b, causes
the lines of force cut by c-d, and e-f to vary from the highest number
of lines that it is possible to cut to zero and back again, thus
constantly changing the flowing direction of the current. The reversal
of the current takes place at the instant that the coil passes the
point where it cuts the greatest number of lines of force. The ends
of the coil are connected to a commutator on the shaft a, b. Steel
insulated brushes pick the current from the commutator ring and conduct
it to the brush post; an insulated wire conductor is attached to this
post and conducts the current to the place of use or storage.
=Voltaic Cell.=--The source of energy of a voltaic cell is the chemical
action. (_See_ accumulator).
=Accumulator.=--The standard accumulator or storage battery is
composed of three cells or hard rubber jars in which a number of
lead plates are immersed in a solution of sulphuric acid and water
known as electrolyte. The plates are stiff lead grids which hold a
paste made of various oxides of lead. Six plates in each cell are
joined to the positive terminal, and seven plates in each cell are
joined to the negative terminal. Thin wooden separators are inserted
between the plates to prevent them from touching one another. In the
forming process the material on the positive plates becomes converted
into brown peroxide of lead; the negative plates assume the form of
gray metallic lead. The material on both plates is known as active
material. When current is taken from the cells the sulphuric acid in
the electrolyte combines with the active material of the plates to form
sulphate of lead, and when the battery is recharged the lead sulphate
is again converted into the original active material and the acid set
free in the solution.
=Storage Battery.=--For construction and action see Accumulator. For
care see chapter on storage batteries.
=Electrolyte.=--A chemical solution used in voltaic cells consisting
of two parts sulphuric acid added to five to seven parts of water by
volume.
=Hydrometer.=--A hydrometer is used to test the electrolyte solution
in the cells of storage batteries. It consists of a weighted float
and a graduated stem, and as sulphuric acid is heavier than water,
the specific gravity reading will be proportional to the amount of
acid. The hydrometer thus measures the relative amount of acid in the
electrolyte and consequently reveals the condition of the battery.
=Ammeter.=--An ammeter is an electrical instrument which indicates
the amount of current that the generator is supplying to the storage
battery, or the amount of current that the storage battery is supplying
for ignition, lights and horn.
=Circuit Breaker.=--The circuit breaker is a device which prevents
excessive discharging of the storage battery. All the current for
lights is conducted through the circuit breaker (Delco system).
Whenever an excessive current flows through the circuit breaker it
intermittently opens the circuit causing a clicking sound. This will
continue until the ground is removed or the switch is operated to
open the circuit on the grounded wire. When the ground is removed the
circuit is automatically restored, there being nothing to replace as is
the case with fuses.
=Switch.=--A switch opens and closes the various circuits and is for
the purpose of controlling the light, ignition, generator and storage
battery circuits.
=Generator.=--See chapter on electrical starting systems.
=Regulation.=--(Delco). On account of the various speeds at which the
generator must operate it is necessary that the output be regulated so
that sufficient current is obtained at the low engine speeds without
excessive current at the higher speeds. The regulation in this case is
what is known as the third brush excitation in which the current for
magnetizing the frame is conducted through the auxiliary or third brush
on the generator commutator. With this arrangement the natural function
of the generator itself causes less current to flow through the shunt
field winding at the higher engine speeds. This weakens the magnetic
field in which the armature is rotating and decreases the output of the
generator.
=Contact-breaker.=--See chapter on Atwater Kent ignition systems.
=Coil, nonvibrating.=--See chapters on Atwater Kent ignition systems
and Philbrin electrical systems.
=Distributors.=--See chapters on Magnetos and Atwater Kent ignition
systems.