Correct Option: B

Given GC(s) =	1 + 6s	....…(i)
	1 + 2s

In phase lead compensator

Vo(s)	= G(s) =	α(1 + sT)	.......…(ii)
Vi(s)		(1 + αsT)

on comparing equations (i) and (ii), we have
T = 6
αT = 2
or α = 2/6 = 1/3
Now,

sin φm =	1 – α	=	1 - (1/3)
	1 + α		1 + (1/3)

or
sin φ_m = 1/2
or
φ_m = 30°
Alternative method

Gc(s) =	1 + 6s
	1 + 2s

Phase shift is φ = tan^–1 6ω – tan^–1 2ω

dφ	=	6	-	2
dω		1 + 36ω2		1 + 4ω2

For maximum value of φ put	dφ	= 0
	dω

∴ 3(1 + 4ω²) = 1 + 36ω²
or
12ω² = 1
or

ω =	1
	√12

Thus,

φ = tan–1	6	- tan–1	1
	√12		√3

tan–1(√3) - tan–1		1
		√3

= 60° – 30° = 30°