Structure of the Hysteresis Dynamometer:
The hysteresis dynamometer consists of:

A hollow-cup hysteresis rotor
Inner and outer stators
Front and rear end caps
A force measurement mechanism
Bearings
The hysteresis hollow-cup rotor is a special metal rotor made from rare-earth-based materials. After heat treatment, it achieves a single-domain or near-single-domain microstructure, giving it a high coercivity.

When the magnetic domains (magnetic molecules) in the rotor rotate within the air gap, their orientation changes with the external magnetic field direction at different positions. However, due to the high friction between magnetic domains, they cannot realign immediately with the external magnetic field when the rotor is repeatedly magnetized, resulting in a hysteresis angle between the magnetic domains and the external field. This hysteresis effect generates a torque, which is non-frictional in nature.

The hysteresis dynamometer is composed of:

A hysteresis brake mounted on a bearing housing
A torque sensor
A speed sensor
Testing Process:
During testing, the motor under test drives the rotor inside the brake to rotate. When the brake is energized with an excitation current, its inner and outer stators apply a braking torque to the rotor (i.e., the motor under test) through the air gap.

At the same time, the brake undergoes slight deflection, causing micro-strain in the sensors. The torque sensor converts the torque into an electrical signal, while the speed sensor converts the rotational speed into an electrical signal. These signals are then displayed on the LCD screen as measured values.