An engine dynomometer is a mechanical device used to simulate actual operating conditions an engine can experience. This can be for a multitude of purposes.
There are three major types of devices used. They are categorized by the way they load the engine and consequently the way they dissipate the energy.
|Inertia Dyno||Hydraulic dyno||Eddy Current Dyno|
From a functional standpoint the inertia dyno can be only used to do Performance (acceleration) testing, the other 2 can be used to do long term testing because they have a method of dissipating the work done to them by the prime mover (engine). The hydraulic dyno uses water to absorb the energy of the engine. The energy is absorbed as heat in the water. The water is then cooled and recycled or wasted. Cool water is constantly carrying away the heat. The eddy current dyno also changes the power absorbed into heat but the heat is not generated by the rotor's direct contact with the water but is generated by the push/pull of electrical forces within the dyno. The eddy current dyno is like an electric motor is reverse.