Crane resistor is mainly used to adjust rotational speed and reduce starting current of motor. Thermal problem shall be paid more attention to for long time use of crane resistor, which is key factor to decide whether it can move safely.

Generally, it must be immediately observed whether crane resistor will be in overheating condition as we use it. Service condition: ambient temperature <= +40°C, average temperature in 24 hours <= +35°, lower limit of ambient temperature shall be -25°C and -40°C; altitude <= 2000m; ambient air shall be clean, relative humid in the highest temperature +40°C shall be not more than 50%, that can be improved in the lower temperature; installation grade III, pollution grade 3 grade; inclination shall be not more than 5° for vertical installation.

To better maintain crane resistor, we could use wire brush, file and abrasive cloth to clean rust on the oxide layer of crane resistor for its good heat dispersion.