A dynamometer is a device that can be used to determine the power required to operate an engine. They also measure the characteristics of torque, rotational speed and power output of a combustion engine, electric motor or other power source. There are two different dynamometer systems that are engine dynamometers and chassis dynamometers.
Engine dynamometers offer the most innovative engine diagnostic tools in the market today. It measures the power and torque directly from the engine's crankshaft when the engine is removed from a vehicle. They are also capable of indicating when the repair is complete, the engine is operating according to specifications and when they are ready to break in engines before installation. Engine dynamometers are mainly used the engine manufacturers themselves. In order to perform the measurements on the engine, the engine has to be connected to the dynamometer with a shaft, however, some new dynamometers can be connected to a computer making it easier to operate giving more precise results.
A chassis dynamometer measures the power delivered to the surface of the drive roller by the drivewheels. These are often found in performance workshops. Due to it measuring the output of an engine through the wheels of a car, the engine doesn't have to be removed from the frame of the vehicle.
The Ac dynamometer is constructed using a low inertia AC motor that is specifically designed for engine tests that are mounted on a substantial baseframe. For trunnion mounted machines, a precision strain gauge load cell is used. Heat generated within the dynamometer is corrupted by the integral cooling fan. The advantages of an ac dynamometer is that it has very low inertia, very fast response and line regenerative whereas the disadvantages are that it can be quite a high cost and it does require high amperage electrical service.
Hydraulic Dynamometers have been designed to be compact, robust and allow easy maintenance. The dynamometer working compartment consist of semi-circular shaped vanes cast into stainless steel rotors. The dynamometer load is controlled by a characterised water outlet valve which is operated by a closed loop electro hydraulic servo system. The power absorbed by the dynamometer is carried away by the water in the form of heat.
Powertrain testing is currently undergoing massive change which is being driven by the challenges that global society are currently facing. The need for reduced dependence on fossil-fuels and improved carbon-footprints are driving changes in the technologies used in all vehicles. This in turn has a direct impact on approaches to testing of Powertrain components and systems.
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