Deseret evening news. [volume] (Great Salt Lake City [Utah]) 1867-1920, 1904-02-05
Street Car Accidents That Have
Caused Many Salt Lakers
To Marvel.
BUT NO ONE IS EVER HURT
Scientific Explanation Of Explosions
That Frequently Happen On Cars
Of This and Other Cities.

Often you have heard a sputter, OBJ
served bright lightning. like fash,
then the lights go out-and the street.
car has stopped with jar, In other
words, you have seen blowout" And
Invariably II GAUGES surprise when the
papers announce that nobody was hurt,
You would rush home and describe the
horror Of the situation, possibly, be.
.lieying no doubt six or eight people had
been killed. 1t has every appearance Of
q serious accident, and frequently 1t
causes "A panic among passengers, but
the truth Is that aside from this pros.
poet Of panic, there is absolutely no
danger to the passengers In this unique,
exciting blowout" Were Il generally
understood the danger OF panic
would be entirely eliminated and to
help people to understand, the Electric
cal Review OF recent date contains the
following explanation: IF steam en-
CINE Is overloaded II will stop and re-
fuse TO work, although the full pres
sure OF steam may remain upon the
piston, and not cause any damage. ON
the other hand, motor when over
loaded. tries lis best to do the work
thrown upon II, II II cannot run at full
speed It will run at whatever speed II
can, AS the speed decreases the cur
rent through the motor Increases, and
the motor adjusts itself TO that speed at
which the turning effort Is sufficient to
cause rotation and do the work. II the
effort demanded OF the motor Is so
great that the current which passes
through II when standing still Is not
sufficient to cause rotation, the motor
rent win continue 10 flow unless inter-
rupted by suitable mechanism.
"The current which viii flow through
a motor when II IL standing still Is In
almost all eases far in excess of that
which the motor Is designed to carry;
and. indeed, In well-designed motor
a current dangerous for the motor will
be reached before the motor has been
stalled. The effect OF this heavy cur
rent on the motor, II allowed TO con-
tinue. Is to heat the wlndings to
dangerous degree and destroy the In
sulation. possibly setting II on fire,
and II is to prevent this occurrence,
whether due Ia careless hadling Of
the car or TO unexpected causes, that
the fuses. are used. a fuse IL simply
a short piece OF wire OF such size that
II viii be melted by current which,
II allowed 10 flow through the motor
for any time, Will damage Il, When a
fuse blows. then, II simply means that
one OF the safety devices on the car
has operated to prevent damage to the
motor The melting OF the fuse opens
the circuit and cuts of the current
from the motor. To protect the car
Ihe fuse Is enclosed In a hreproof box.
There Is another device for accom-
plIshing this purpose. which Is known
MS the circuit breaker. This Is q switch
by an electromagnet, which
opens whenever the current reaches a
certain dangerous value. This mechan-
Ism Is now generally installed upon
electric coils In addition to the fuse, II
Is often placed on the roof OF the plat
form over the motorman's head, where
Il is easily reached and Il Is set TO
operate at higher current value than
he fuse. because the circuit breaker
acts almost instantaneously while II
lakes little time for the fuse to be
melted Now motor car can stand
FOR n second or two current which
would destroy II II applied for a long
,r period. The circuit breaker then,
.akes care OF heavy overloads and the
fuse protects the motor against those
smaller currents which are dangerous
Il applied for a considerable time,
when a fuse blows there Is gener-
ally volatllIzation OF the metal Of
The fuse and a slight explosion. These
explosions usually cause report and
some smoke. When the circuit break
pr Ia opened It draws ala electric arc
In breaking the circuit, and as In this
arc a considerable amount Of energy Is
llssipated In hating the air there
may be here also something OF an eX-
plosion, but In neither case Is there any
Hanger TO the passengers when the APP
paratus Is properly installed. The fuse
and the circuit breaker are safety de-
Vices, the operation Of which indicates
not that there Is danger TO those on the
var but that danger TO the motors has
been ayerted."