Published On: Tue, Mar 3rd, 2020

Contemporary electrical installations and electric drives on steel structures – Illustrated

Author: Radoje Jankovic

All photos are original of author

Contemporary electrical installations and electric drives on steel structures – Illustrated

In modern surface exploatation lignite in large open pits are used the most modern mining machinery and equipment is very large in size and capacity.

Only one system; Rotary excavator  – belt conveyor – spreader has a mass (weight) of 40 000 to 60 000 tons and often up to 100 000 tons in the case of the open pit mines in Lazarevac, Serbia.

Between tracked excavator rodents and last spreader delaying overburden weight to landfill, either external or internal is the whole system of belt conveyors with a total length goes up to 20 or more kilometers, includes 10 or more individual belt conveyors individual length and up to 1.5 km.

Power supply these systems with a huge and very complicated electrical installations, electric motor drives and complex electrical and electronic equipment are high-voltage alternating current; 6, 10, or 35 kV, 50 Hz. Since the beginning of the system; Excavator – Conveyor – Spreader along the belt conveyor is sometimes laid over 100 km high-voltage, 35 kV cables, almost as optical cables (which have replaced over 300 km of LV cables for control, signaling and automation along the belt conveyors), and of course 80-100 km low voltage cables, 3 x 400/230 V AC, necessary for electric lighting, electrical maintenance and other needs maintenance work along the belt conveyor.

In this lesson, I shows a “small”  part of electrical installation through the details of my original photographs that have never been published anywhere .

Photos showing almost all the elements, and most importantly, professionally performed the electrical installation and assembly of electrical equipment in one called sliding train, earlier known as the reloading the trolley. This sliding table has been mounted on the top belt conveyor from which the waste rock excavated from the early system switches to the last link of the system, the spreader  that the same deposited on tailings dump which may be external (around the perimeter of the surface digs) or internal (tailings are disposed in the interior of which, ie. work in which he completed in coal mining).

This wagon has a sliding speed of 2 – 6 m / min, synchronized with the speed of movement of labor and spreader, 24 is powered by three-phase asynchronous motors power 1.5 kW, which is powered by the soft starter each individually, voltage 400 V, 50 Hz. In order to avoid problems at rails “skewed” wheels that are driven by individual motors, soft starter 24 synchronization is performed via one of these built-in front of 24 soft starters. In this case, the sliding train transport works well, almost glides along the rails following the track.

Fig. 1. This image shows a rig on the last belt conveyor in the series BTO system called the landfill conveyor, because this has been transferred to the tailings excavator tray that is also seen in the picture. It is clearly seen that the tape receiving excavator trays placed under the “head” rig over the tailings from the feed switches to a tray on the same deposited at the landfill.
The photo I took during the switching excavator trays with conveyor belt to the working position of the inner surface mine dumps .

Fig. 2. One of 24 asynchronous electric motor for driving the sliding train synchronized with the tray excavator.
All 24 drive motors are released into operation simultaneously over 24 soft starter whose work sinhronizes main soft starter who is in front of these 24 soft starter.

Fig. 3. One view of the drive train electric motors slide.
The picture is clearly visible cable installation that was performed fine-wires of power cables for heavy-duty, placed in protective plumbing pipes in construction to the sliding of the train. Professionally executed electrical installations, which must last at least 50 years and even more.

Fig. 4. Detail of supplying cables layed inside the protection installation tube for asynchronous motor of 1,5 kW, 400 V AC.

Fig. 5. Details of laying power cable for supplying of driving asynchronous motors via soft starters.
You can see, perfectly erected works on the cable laying for duration over 50 years of exploration of this machine.

Fig. 6. Detail of power cables laying and protection installation tubing used for cable protection against mechanical damages. Green cable is single wire protection grounding system which is very carefully and massive worked for protection against touch voltage and the voltage of error.

Fig. 7. Details of flexible laying of power, protection (ground) and control cables on the slide rail cars via air.
As you can see, this is practical art works of high experienced electrical experts.

Fig. 8. Control boxes in the slide cars.
Really artistic work of high experienced electrical experts.
Nothing is not forgot.
You can see cables, steel installation tubing for cable protection… Each cable is signed according to project for lighter maintenance during long duration of operation of this machine…. etc.

Fig. 9. One view more on the slide car passing control boxes and details of installation tubing for cable protection.

Fig. 10. View on the train on the right side of slide cars and driving asynchronous motors. 12 motors on one side of the cars.
Also, you can see, details of electrical installation made by fine-wire power and control cables laying through the air, passing from one to other part of steel structure and through protection steel tubing.

Fig. 11. Detail of the receiving conveyor of excavator trays wrapped with sliding reloading train on the belt conveyor length of about 1000 meters.

Fig. 12. This image shows a complete electrical motor-driven transport of a large caterpillar excavator rodent (rotary excavator), which has six transport caterpillars.
Power supply voltage of the motor is done alternating voltage three-phase 3×690 V, 50 Hz, by electronic frequency inverter power due to the necessary fine control speed of the excavator, which is 6 m / min.

The blue box between the three – phase motor and gearbox protection electro-hydraulic brake that drives a small electric motor and that each driving motor must have.

Weight (mass) of the excavator is over 3,000 tons, a supply voltage of 35 kV, 50 Hz, via a separate cable drum that has an 1.5 km high voltage of 35 kV cable, which automatically via a special mechanism unwound if the excavator moves forward or rewinding if backhoe going backwards.

No reference. Original work of author.

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Contemporary electrical installations and electric drives on steel structures – Illustrated