Editing Dynamometer (section)

===Hysteresis dynamometers===
Hysteresis dynamometers use a magnetic rotor, sometimes of AlNiCo alloy, that is moved through flux lines generated between magnetic pole pieces. The magnetisation of the rotor is thus cycled around its B-H characteristic, dissipating energy proportional to the area between the lines of that graph as it does so.

Unlike eddy current brakes, which develop no torque at standstill, the hysteresis brake develops largely constant torque, proportional to its magnetising current (or magnet strength in the case of permanent magnet units) over its entire speed range.<ref>{{cite web |url=http://www.magtrol.com/manuals/hbmanual.pdf |title=Hysteresis Brakes and Clutches |work=Magtrol Inc. |location=US |date=October 2019 |access-date=2023-01-02}}</ref> Units often incorporate ventilation slots, though some have provision for forced air cooling from an external supply.

Hysteresis and Eddy Current dynamometers are two of the most useful technologies in small ({{convert|200|hp|abbr=on}} and less) dynamometers.