1. When the DC high-power speed regulating motor runs to a stable temperature rise, use a multimeter to measure the winding resistance, usually zero to several ohms;
2. Rotate the motor by hand, if the resistance is obviously larger, it means that there is a short circuit inside the motor;
3. Connect the positive and negative poles, there will be a lot of resistance when twisting by hand, indicating that the circuit is normal, otherwise there will be a circuit breaker inside;
4. Investigate commutation sparks when switching on. No spark is best. Sparks are outstanding, sparks are poor. If there is a ring fire, the speed regulating motor cannot be used;
5. Add extra voltage, measure the speed, and indicate that the error of the speed should not exceed 10;
6. After running until the temperature rise is stable, the surface temperature of the motor should not exceed 80 degrees Celsius. If it exceeds, it means that the temperature rise of the motor is unqualified;
7. Add 1.2 times the extra voltage and let the speed regulating motor run for 2 minutes to see if there is any abnormality.