12 Pulse Configuration for DC Drives ?

Q1 ) Can we say that 4 Quadrant DC drives as a 12 pulse drive ?

This is not necessarily true. A 4 Quadrant (or regenerative) DC drive must have (at least) 12 pulse drive , it doesn't mean all 12 pulse drives are 4 Quadrant (or regenerative) drives.

For detail, see the thread (and the associated links in the thread): http://cr4.globalspec.com/thread/53514/Four-Quadrants-or-regenrative

Q2 ) Is the no. of pulse decided by transformer configuration and no. of thyristors ?

I would say it is primarily by the number of thyristors. The transformer can be either three winding or phase shifting transformer for the drives of 12 pulse or 18 pulse etc.

For detail, see the thread (and the associated links in the thread): http://cr4.globalspec.com/thread/41391/VFD-and-Pulse

- MS