Question { 4943 }

What meant by XLPE cable

Answer

Cross-linked polyethylene

Question { L&T, 4380 }

why is that a 4*4mm cable,is always powdered internally

Answer

Answer 1 is correct. When the outer insulation is put on it
is hot and will stick to the inner insulation. The powder
stops this from happening.

Question { GSK, 6878 }

One 15kw motor Why we used star delta feeder?why not used DOL
please explain in details

Answer

The star delta starter limits the starting current of the
motor by reducing the voltage across each winding. In star
the voltage is equivalent to the phase to neutral of the
power supply. In delta the phase to phase voltage is
applied across the windings.
With a DOL starter the phase to phase voltage is applied
across the windings. The starting current can be in excess
of 7 times the full load current.
The main reason for using star delta starters is that the
power supply system to the motor does not have to support
the high current needed for DOL starting. If the power
supply is not able to supply the current a voltage dip will
occur affecting all other users on the supply.

Question { NTPC, 4665 }

Why can not you store AC power in battery like DC power?

Answer

The problem is that while DC current flows in one direction
only AC reverses direction every half cycle.
What this means is the when connected with +ve to +ve and -
ve to -ve DC will flow into the battery and charge it. With
AC you will have +ve to +ve one half cycle and -ve to +ve
the next half cycle. In effect you will charge the battery
one half cycle and discharge the battery in the next half
cycle. Although in reality you would probably damage the
battery.

Question { 3565 }

in fuel level controller what is MOV please define.

Answer

Most likely what you are looking at is a Metal Oxide
Varistor. This a a component which will start to conduct
when the voltage across it reaches a pre-designed level.
They are normally used to absorb spikes where these can
damage electronic components. Placing a MOV across the
input will shunt any spikes through the MOV and prevent it
from damaging other components.

Question { Prism Cement, 3397 }

Why in India only 50hz frequency not 60hz

Answer

At first each electricity supplier had their preferred voltage (AC or DC) and frequency. Initially 25, 50 and 60 Hz were used. 25 Hz was good for motors but not for lighting as there would be a visible flicker. When electricity became more widespread each country decided to have a voltage and frequency standard. Europe mostly selected 50 Hz and America 60 Hz. India selected 50Hz.
Any type of electrical equipment can be built to use either 50 or 60 Hz. Not as stated in the previous answer "But in America is used advanced equipments only it's operate on 60hz frequency only".