The evening star and Newark advertiser. [volume] (Newark, N.J.) 1907-1908, 1907-07-10
KEEP YOUR SEAT
BESTTHING TOD0WHEN.
FUSE BLOWS OUT.
About the only Danger to Trolley
Passengers Is That of
a Panic.

About the only danger to passengers
In electric cars when a fuse blows out
with much smoke inc noise lies III the
possibility of a panic. There ia n most
unexpected explosion right under the
car, a big puff of smoke, a smell of
burning rubber and a stalled car, but
really nothing else to get excited about.
says the Kansas City Journal.
The reason why there Is usually a
stampede when the car fuse blows out
is because fuses are a mystery to a
majority of passengers. AS a matter
of fact, fuses are merely safety valves.
and when they blow out 1t Is to prevent
an accident, just as the safety valve
of a steam engine blows off to prevent
the boiler from being blown to hits by
an overpressure of steam
If a steam engine is overloaded It
will stop and refuse to work, although
the full pressure of steam may impinge
upon the piston and not cause danger.
On the other hand, a motor, when over
loaded, tries its best to do the work
thrown upon 1t. If it cannot u at
full speed it will run at whatever speed
1t can. AS the speed decreases. the
current 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.
The current which will flow through
a motor when 1t Is standing still is. in
almost all cases, far in excess CO that
which the motor is designed to carry,
and In a well designed motor q current
dangerous for the motor will be reached
before the motor has been stalled. The
effect of this heavy current ON the
motor, If allowed to continue, Is 10 heat
the ~windings to a dangerous degree and
destroy the insulations, possibly setting
them on fire, and it Is to prevent this
occurrence. whether due TO carelessness
in handling the car or unexpected
causes, that fuses are used.
A fuse is simply a short piece of wire
of such size that it will be melted by
a current which, If allowed to flow
through the motor for any time, would
damage 1t. When the fuse blows 1t
simply means one OF the safety devices
on a car has operated to prevent dam
age to the motor. The melting of the
fuse opens the circuit and cuts off the
current from the motor. To protect
the car, the fuse is inclosed in a fire.
proof box.
There is another device for accom-
plishing the purpose, which is known
as a circuit breaker. This is a switch
controlled by an electro-magnet, which
| opens as soon as the current reaches a
certain dangerous value.
This mechanisf Is now generally in
| stalled upon electric cars in addition to
the fuse. 1t is often placed over the
motorman's head, where 1t IS easily
reached, and is set to operate ut a
higher current value than the fuse, be-
cause the current-breaker acts almost
instantaneously, while it takes q little
time for a fuse to be melted. A motor
can stand for a second or two o cur
rent which would destroy 1t If applied
for a longer period. The circuit then
takes care of heavy overloads, ard the
fuse protects the motor against those
smaller currents which are dangerous
If applied for a considerable time.
When a fuse blows there is generally
a volatilization of the metal Of he fuse
and a slight explosion. Those explo-
sions usually cause a report and some
| smoke. When the circuit breaker is
opened 1t draws an electric arc In
breaking the circuit, and as In this arc
a considerable amount of energy is dis
sipated in heating the air, there may be
something of an explosion, but In
neither case is there any danger to the
passenger when the apparatus IS pro-
perly installed.
The fuse and the current-breaker are
safety devices, the operation of which
indicates not that there is danger to
those on the car, but danger to the
motors has been aVerted.