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DYNAMOMETERS

Motor and engine testing dynamometers apply braking or drag resistance to motor rotation, and measure torque at various speeds and power input levels. These devices measure the output torque of motors, engines, gearboxes, transmissions, and other rotary machines.

Dynamometers use different methods to induce a braking force on the device under test. Generally we can classify the Dynamometers into four types: Brake  or Friction Dynamometers Hydraulic Dynamometers Electrical Dynamometers & Electronic Dynamometers            What exactly are the benefits of different dynamometers? The following chart describes the benefits of water brakes, Eddy Current, AC, and DC dynamometers. Hydraulic | Eddy Current| DC Dynamometer | AC Dynamometer Features Water Brake Eddy Current DC AC Motoring ability No No Yes Yes Inertia Low Varies High Low Control stability Low Good Very Good Excellent Speed capability High High Moderate High Power line regeneration No No Yes Yes Control response Slow Moderate Fast Fastest Cooling requirements High High Low Low Electrical requirements None Low High High Technology Old Old Old New Power Range High High Moderate Moderate Friction Dynamometers In a prony or friction brake dynamometer the braking mechanism uses friction pads or brake shoes to engage the rotating disk or drum coupled to the motor. Sometimes, the  dynamometer uses a rope or a belt that is wound around the flywheel of the engine. One end of the belt is attached to a spring balance whose other end is fixed to the ground. the other end of the belt is attached to a load hanger that suspends freely. when the load is to be changed load is added to the hanger or it is taken out of it. The braking torque can then be calculated as the product of the net force on the brake and the load arm. Brake power can then easily be calculated by the formula: b.p. = (2  π N T)/60    (in KW)   Prony brake dynamometer                 Hydraulic Dynamometers                      (Water Brake Dynamometer)   In a hydraulic or water brake dynamometer, braking drag is applied to the dynamometer rotor vanes via water circulating between the rotor and the stator housing. A hydraulic or a water brake is a bladed rotor that churns water inside the dynamometer housing. The more water inside, the greater the braking force exerted on the device under test.   Advantages Disadvantages Low cost Low inertia Difficult to control High maintenance                 A hydraulic dynamometer                              Taylor's dynamometer water brake     Visit SACMoney.Com for Money... Success... Revenue!!! Electrical Dynamometers a.   Eddy Current Dynamometer   An Eddy Current dynamometer produces braking torque using the principle of eddy currents induced in a rotating metallic disk, immersed in a magnetic field. Advantages Disadvantages Low maintenance Precise control Widely accepted in the automotive industry High inertia More expensive   An eddy current dynamometer b.   DC Dynamometer     A DC dynamometer is a DC motor that has been trunnion mounted. DC dynamometers are essentially DC motors mounted and configured to provide drag against the motor being tested and output the resultant torque and power. Advantages Disadvantages Motors and absorbs Fast response Air cooled (no water required) Line regenerative High cost (dynamometer and power amplifier) High inertia Requires high amperage electrical service                 A DC dynamometer   c.   AC Dynamometer An AC dynamometer is similar to a DC dynamometer except it uses an AC motor and is powered by alternating current. AC dynamometers are essentially AC motors mounted and configured to provide drag against the motor being tested and output the resultant torque and power.  Advantages Disadvantages Motors and absorbs Very low inertia Very fast response Line regenerative High cost Requires high amperage electrical service  An AC dynamometer

Electronic Dynamometers

 

Electronic dynamometers are essentially, the electrical dynamometers, equipped with extensive electronics to measure different parameters related with the engine quickly with a great precision. These dynamometers are provided with electronic sensors  and transducers that measure forces and temperature of different parts of the engine and directly give results in the form of electric pulses. Then these dynamometer calculate different parameters using a self computer and display them on the digital screen normally placed on user friendly display panels. Different parameters like load, etc can be increased or decreased from the panel and can be set accurately.

An electronic Dynamometer console panel

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APPLICATIONS

Common applications for dynamometers include general purpose, automotive, aircraft or aerospace, chain or belt drives, gearboxes, fluid power systems, gas or diesel engines, industrial, marine, transmissions, and turbines. All dynamometers will typically have speed and power feedback for performance testing and monitoring. Typical features include encoders or other speed / position sensors, torque arms, and reaction sensors. Common dynamometer interfaces include integral control console, separate console, computer, or modem or remote control. Features common to dynamometers include PID control, flow control or throttling, data acquisition or logging, alarms, motor power analysis, and engine exhaust analysis.

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