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In a concrete batching plant, the mixer and the aggregate conveyor have very different load characteristics; their motors are not chosen with the same logic. The mixer motor is sized for the torque to turn a stalled mix again with the pan full, while the aggregate conveyor motor is sized for the capacity to start an inclined, loaded belt.
Mixer motor
Twin-shaft and planetary mixers work with arms turning slowly through a gearbox. In the normal cycle the mixer is started with the pan empty and material is added afterwards; but during a power cut the pan stays full and concrete that has begun to set makes restarting very difficult. Twin-shaft mixers usually have two motors, with synchronous rotation of the two shafts ensured mechanically; the motors must be selected with the same power and speed.
- Pan volume and mix type (dry, wet)
- Gearbox ratio and input connection
- Nameplates of the existing motors
- Whether water reaches the motor during pan washing
Aggregate conveyor motor
The aggregate conveyor carries weighed material from the bins to the mixer. Its power follows from belt length, angle of incline, capacity and belt speed. When an inclined belt stops full of material, on restart it must both lift the load and accelerate the belt. The anti-rollback device sits on the gearbox or pulley side; the motor’s job is to provide enough torque for a loaded start.
Dust, cement and the outdoor environment
Cement dust can form a hardening layer on the fan cover and cooling fins. The motors need regular cleaning, sun and rain protection on open sites, and wash water should not be aimed straight at them. The IP55 protection of DRG motors covers dust and low-pressure water jets; it is not designed for high-pressure washing.
For the plant’s other drives (cement screw, compressor, water pump) see the concrete batching plant electric motors page, and match the motors whose power and speed are known in the online motor shop.