Crane Motor Duty

Crane motors and metallurgical frequency control motors are squirrel-cage rotor motors. It integrates the advantages of traditional hoisting metallurgical motors and variable frequency motors, so that the motor can not only meet the needs of frequent starting, braking, overload, reverse rotation, over-speed, shock and vibration work, but also meet the needs of frequency converter control. If necessary, realize soft start, four-quadrant operation, etc., so as to reduce the impact on the equipment and save energy.

Crane motors often encounter driving equipment with high starting frequency, such as: walking driving equipment. In this case, the decisive factor in selecting a motor is not the required power, but the number of motor starts. Each time the motor is turned on, a high starting current is generated, causing the motor temperature to rise too high. If the heat generated by the motor is greater than the heat emitted by the ventilation system, the windings will overheat and burn. The ability of the motor to withstand thermal loads can be improved by selecting the appropriate insulation class or using forced cooling fans.

Usually the motor is designed according to its thermal load. Generally, the motor is designed and manufactured according to the working system of S1 100% cdf or S3 40%. Based on the load torque, the calculated power should be equal to the rated power of the motor.

According to the general working characteristics of the crane, the S3 40% duty motor is often used, which corresponds to the crane A6 working duty. It means that the crane work is divided into 6 cycles per hour, each cycle is 10 minutes, and 40% of the time is working ( 4 minutes) and the remaining 60% not working (6 minutes).

For cranes that are actually used more frequently, corresponding motors need to be selected. See Tables 1 and 2 for power conversion between motors with different work duty .

Table 1

Work Duty

S1

S2

S3

S4/S5(CZ=150)

S4/S5(CZ=300)

S4/S5(CZ=600)

100%

30min

60min

15%

25%

40%

60%

100%

25%

40%

60%

40%

60%

60%

Power (kw)

0.87P

1.2P

P

1.35P

1.2P

P

0.885P

0.725P

0.925P

0.825P

0.75P

0.7P

0.6P

0.475P

Note：P is the power of S3 at 40% work duty

Table 2

Work Duty

S1

S2

S3

S4/S5(CZ=150)

S4/S5(CZ=300)

S4/S5(CZ=600)

100%

30min

60min

15%

25%

40%

60%

100%

25%

40%

60%

40%

60%

60%

Power (kw)

P

1.2P

1.1P

1.4P

1.3P

1.15P

1.1P

0.83P

1.06P

0.95P

0.86P

0.8P

0.7P

0.54P

Note: P is the power of S3 at 40% work duty

For more motor working duty please check

Teach You To Know The 10 Working Duty Of Electric Motors