Factors to consider when choosing a dynamometer and precautions

　　1. In the testing of AC/DC motors and power tools, testing equipment such as dynamometers is often used, mainly to test the motor's torque, speed, and output power.

　　However, not everydynamometercan meet all motor testing requirements, and three main factors need to be considered:

　　First, the range of torque testing; the torque of the dynamometer usually cannot exceed the maximum torque. If all tests are completed in a short time, there generally won't be major issues.

　　Second, the speed testing range; the speed of the dynamometer usually cannot exceed the maximum speed. Long-term use will greatly shorten the lifespan of the dynamometer, especially due to mechanical wear.

　　Third, the power usually marked on the dynamometer refers to the power that the dynamometer can absorb, as general dynamometers (hysteresis, magnetic powder, eddy current dynamometers) absorb energy consumed as heat from the output power of the tested AC/DC motor or power tool. Strictly speaking, this indicator should not be exceeded; otherwise, the dynamometer can easily burn out due to heat dissipation issues.

　　2. The selection of a dynamometer must not only meet the three main technical indicators of speed, torque, and power but also consider whether it meets the specific testing requirements. Generally, motors need to test parameters such as no-load speed, no-load loss, and stall torque, which also need to be given special consideration!

　　3. When selecting a dynamometer, it is best for all testing data of the motor to be between 30% and 90% of the dynamometer's performance parameters, as the testing accuracy of the dynamometer is most guaranteed within this range. Therefore, it is mainly divided into three parts: the mechanical part of the dynamometer, the accuracy range of the speed and torque sensor, and the display accuracy of the speed, torque, and power measurement device.

　　4. Commonly used dynamometers mainly include the following categories: hysteresis dynamometers, magnetic powder dynamometers, asynchronous dynamometers (power dynamometers), eddy current dynamometers, and less commonly used dynamometers (permanent magnet synchronous motors, servo motors, etc.).

　　According to the achievable speed, the order of dynamometers is eddy current dynamometers, asynchronous dynamometers, hysteresis dynamometers, and magnetic powder dynamometers.

　　(1) Eddy current dynamometers and asynchronous dynamometers cannot cause the motor or power tool to stall, but their upper speed limit is very high, usually between 20,000 and 30,000 RPM; torque can also be very large.

　　(2) Hysteresis dynamometers generally have speeds below 20,000 RPM but can be locked, though the power should not be too high; torque is generally less than 20 Newton-meters.

　　(3) Magnetic powder dynamometers have low speeds, generally between 1,500 and 5,000 RPM, but torque can be larger, and the motor can be locked.

　　5. Generally, asynchronous dynamometers do not require water cooling, only air cooling; eddy current dynamometers, hysteresis dynamometers, and magnetic powder dynamometers require both water cooling and air cooling. Some low-power hysteresis dynamometers can meet testing requirements without water cooling, and the cooling function must be turned on when using the dynamometer.