Correct Answer - Option 2 : 8 MJ / MVA
Inertia constant (H):
Inertia constant is defined as the ratio of the kinetic energy of a synchronous machine to the rating of the machine (in MVA).
The units of the inertia constant are in MJ / MVA or MW-sec / MVA.
Formula:
Kinetic energy stored in the synchronous system can be expressed as
K.E. = H S
S = Rating of the machine.
Calculation:
Given that,
S = 50 MVA
Kinetic energy K.E. = 400 MJ
⇒ KE = H S
⇒ H = 400 / 50
∴ H = 8 MJ / MVA.
