Behavior of synchronous machines subjected to transient overvoltages

Voltage transients play an important part in the area of power quality. Transient overvoltages cause machine tripping due to breaking by overvoltage protection, which may lead to production losses. Apart from that, large torque peaks that may cause damage to the shaft or equipment connected to the shaft. High current peaks occur as well, which leads to thermal heating and tension. This paper shows on what conditions transients cause high peak torques and currents for synchronous machines, which is explained by a simple theory. Simulations verify the theory, and illustrate the torque and current peaks dependence on transient duration and magnitude.