The commonly used dynamometers are mainly classified into the following categories: hysteresis dynamometers, magnetic powder dynamometers, asynchronous dynamometers (electric dynamometers), eddy current dynamometers, and less commonly used dynamometers (permanent magnet synchronous motors, servo motors, etc.). The order of the dynamometer according to the achievable speed is: eddy current dynamometer, asynchronous dynamometer, hysteresis dynamometer, magnetic powder dynamometer;
(1) Eddy current dynamometer and asynchronous dynamometer cannot achieve locked rotor of motors or electric tools, but their upper limit of speed is very high, usually 20000~30000 RPM; The torque can also be very large.
(2) The speed of a hysteresis dynamometer is generally below 20000 revolutions per minute, but it can achieve locked rotor, but the power is not too high; The torque is generally below 20Nm.
(3) The speed of the magnetic powder dynamometer is relatively low, usually 1500~5000RPM, but the torque can be increased and the motor can also achieve locked rotor.