Constant force The dynamometer has a "braking" torque regulator - the power absorption unit is configured to provide a set braking force torque load, while the prime mover is configured to operate at whatever throttle opening, fuel delivery rate, or any other variable it is desired to test.
Constant speed. If the dynamometer has a speed regulator (human or computer), the PAU provides a variable amount of braking force (torque) that is necessary to cause the prime mover to operate at the desired single test speed or RPM. The PAU braking load applied to the prime mover can be manually controlled or determined by a computer.
Electric motor/generator dynamometer. Electric motor/generator dynamometers are a specialized type of adjustable-speed drive. The absorption/driver unit can be either an alternating current (AC) motor or a direct current (DC) motor. Either an AC motor or a DC motor can operate as a generator that is driven by the unit under test or a motor that drives the unit under test.
Hysteresis Brake Dynamometers (HD Series) are versatile and ideal for testing in the low to medium power range (maximum 14 kW intermittent duty). With a Hysteresis Braking system, the Dynamometers do not require speed to create torque, and therefore can provide a full motor ramp from free-run to locked rotor.
The Powder Brake Dynamometer (PB Series) contains, as its name suggests, a magnetic powder. The electrical current passing through the coil generates a magnetic field, which changes the property of the powder, thus producing a smooth braking torque through friction.