Question { IBM, 82163 }

what is the function of starter & choke in the tube light
set & how choke give 1000 volts while switching on.

Answer

we need around 800 to 1000 volts to start ionisation of the
medium which is present between the 2 electrodes of the
tube.once the ionisation starts the conductivity of medium
increases and 110 volts is sufficient to sustain the
emission of electrons from electrodes.
so to produce such a high voltage we are using choke.
once it starts to reduce the 230V to 110 volts we are using
the same choke.
so how this choke is producing around 800 to 1000 volts at
starting.
as we know inductor opposes the rate of change of current.
here we are making current I which is intially drawn to
zero with the help of bimetallic contacts present in
starter.according to formulae E=L*di/dt here L is constant
and di is equal to I-0 and dt is time taken for I to become
zero.
accordingly high voltage is induced and this voltage is
sufficient to drive the electrons from one electrode to
another electrode inspite of medium present between
electrodes. once tube start conduction, it needs only 110v
to sustain the illumination.so to reduce the 230v to 110v
choke just acts as a voltage limiter by dropping the
voltage.

Question { ABB, 72198 }

What is the difference between Isolator annd Circuit
Breaker.

Answer

isolator is a off load device which is used for isolating
the downstream circuits from upstream circuits for the
reason of any maintanance on downstream circuits. it is
manually operated and does not contain any solenoid unlike
circuit breaker. it should not be operated while it is
having load. first the load on it must be made zero and
then it can safely operated. its specification only rated
current is given.

but circuit breaker is onload automatic device used for
breaking the circuit incase of abnormal conditions like
shortcircuit, overload etc., it is having three
specification 1 is rated current and 2 is short circuit
breaking capacity and 3 is instantaneous tripping current.