Torque in Generators

The shaft torque of a generator is measured in Newton-meters (symbol N-m), or in pound-feet or pound-inches (lb-ft or lb-in). A torque of 1 Newton-meter represents the force of rotation created by a force of one Newton acting tangentially at a distance of one meter from the center of the shaft. Shaft torque is related to power and speed of rotation as follows:

For example, what is the shaft torque required for a 5kW generator operating at 1800 rpm?

Notes:

1. At very low power, bearing friction and windage may add significantly to the torque required to produce a specific amount of power. (Windage is the air resistance to rotation).
2. At high power, losses through resistive heating of armature windings may significantly reduce the power delivered by the generator. These losses can be partially controlled by forced cooling of the generator. In alternating current generators, reactive elements (inductance, capacitance) in the generator and in the load can also degrade the effective output from a given shaft torque.