For 192 bit key(AES-192), there are 6 columns of 32 bit each i.e 4x6 Matrix. These 192bits of Master Key are shown as k0,k1...k5, i.e 6 words of 32 bit each.
(See page 44 of Book "The Design of Rijndael")
Now k6 will be
k6 = SubByte((RotateWord(k5)) xor K0 Xor Rcon1
k7 = k6 xor k1
k8 = k7 xor k2
and so on...
Since the state in al variants of AES is 128 bit(its the key which is either 128 or 192 or 256 bit) i.e 4 words of 32 bit, the Round Key 0 will consist of k0,k1,k2,k3. The Round Key 1 will consist of k5,k6,k7,k8 and likewise.
We only need 13 x 4 = 52 keys, because the input state is still of 4 words of 32 bit each (128-bit) and each Round Key is also 128 bit. Its only the Master Key which is 192-bits(6 words of 32-bit)
This Animation explains AES-128.