This paper extends the analysis of synchronous machines previously published by Doherty and Nickle to include the calculation of torque due to single-phase short circuit. The torque is expressed as the sum of odd and even harmonic series which are simply related to those previously derived for the armature current. The effect of amortisseur windings is also taken into account. As an illustration of the application of the equations, the short-circuit torque is calculated for a 100,000-kva. generator. The mathematical analysis is given in Appendixes as follows: A. Short-circuit armature current. B. Short-circuit torque. C. Decrement factors. D. Single-phase and three-phase reactances.