Question { vguard, 11687 }

What is double delta conection in AC Motor? And can we done
the double RPM of the motor by double delta conection?

Answer

Double delta connection is used to achieve reduced voltage
during start up of a motor by changing a delta connected
winding from parallel groups to series groups.This is termed
as "double delta connection" because the delta winding is
connected in series during start up and the same is connected
in parallel during running condition with the help of a part
winding starter.Since all winding's are connected in starting
as well as running conditions the amount of heat generated is
not so severe.

Question { 7912 }

The objective of connecting a resistance and capacitance
across gate circuit is to protect the SCR against

Answer

The objective is to protect SCR against high dV/dt.The
protection is called as Snubber Circuit.It is a series
combination of resistor 'R' and capacitor 'C'.The capacitor
'C' is used to limit the dv/dt across the SCR.The resistor 'R'
is used to limit high discharging current through the SCR.

Question { iGate, 7293 }

how to swap all the values without using temporary variable.
tha values r a = 20, x=60 and p=2.

Answer

x=x*a; (x=1200)
a=x/a; (a=60)
x=x/a; (x=20)

p=p*x; (p=40)
x=p/x; (x=2)
p=p/x; (p=20)

Hence final values are a=60,x=2,p=20

Question { IIT, 8000 }

what is a FACTS devices? what is mean by STATCOM????

Answer

FACTS stands for "Flexible AC Transmission Systems".FACTS are employed in power systems to enhance controllability,power handling and power transfer capacities of a power system.These are static devices and operate on the basis of power electronic principles.
A static synchronous compensator (STATCOM)is a regulating device used on AC transmission networks. It is based on a power electronics voltage-source converter and can act as either a source or sink of reactive AC power in a power system.