Answer / ashok

for traction application we preferred dc series motor.
becas its starting starting torque is high

Answer / subramanyam

Voltages used are 1.5kV DC and 25kV AC for mainline trains.

Calcutta had an overhead 3kV DC system until the '60s.

The 1.5kV DC overhead system (negative earth, positive
catenary) is used around Bombay (This includes Mumbai CST -
Kalyan, Kalyan - Pune, Kalyan - Igatpuri, Mumbai CST -
Belapur - Panvel, and Churchgate - Virar). There are plans
[2/04] to change this to 25kV AC by 2010. In preparation
for this, BHEL has been retrofitting some EMUs with AC
drives to allow them to operate with both DC and AC
traction as the system conversion proceeds. Conversion to
25kV AC has already been done on the Titwala-Kasara
section; next to be converted are Khapoli-Vangani, Vangani-
Thane, and Titwala-Thane. The Madras suburban routes
(Madras-Tambaram in the '60s, extended later to Villupuram)
used to be 1.5kV DC until about 1967, when it was converted
to 25kV AC (all overhead catenary supply). (This is where
the MG DC locos were used, e.g., the YCG-1 series.)

The 25kV AC system with overhead supply from a catenary is
used throughout the rest of the country. The WCAM series of
locomotives are designed to operate with both DC and AC
traction as they move towards or away from the Bombay DC
section. The new [2003] AC-DC EMU rakes used in Mumbai are
also designed to operate with both DC and AC traction as
the Bombay area switches over to the 25kV AC system. Read
more about Mumbai area electrification.

The Calcutta Metro uses 750V DC traction with a third-rail
mechanism for delivering the electricity to the EMUs.

The Calcutta trams use 550V DC with an overhead catenary
system with underground return conductors. The catenary is
at a negative potential.

The Delhi Metro uses 25kV AC overhead traction with a
catenary system on the ground-level and elevated routes,
and uses a rather unusual 'rigid catenary' or overhead
power rail in the underground tunnel sections (Line 2).

diameter of cable and core is doubled then the value of capacitance is

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