BELAZ. Traction and speed performance comparative analysis of mining dump trucks with hydromechanical transmission and electric drive BELAZ

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1 Traction and speed performance comparative analysis of mining dump trucks with hydromechanical transmission and electric drive

2 Under equal conditions the speed performances of dump trucks with hydromechanical transmission and electric drive differ in a minor way. To be certain of that, it is sufficient to look at the combined diagrams of the traction and speed performances of and dump trucks, which are the models of one and the same dump truck. The difference between them is the type of drive: is equipped with a six-stage hydromechanical transmission, and is equipped with КТE-90 AC traction electric drive. Principal characteristics Payload capacity, kg Gross weight, kg Engine Cummins QST 30-C Cummins QST 30-C Engine power 783 kw 783 kw Fuel rate, g/kw*h Transmission hydromechanical electric drive 6+1 КТE-90 Max speed, km/h Body volume, m³ struck 60 37,7; 44,5; ,7; 44,5; 75 heaped 2:1 53,3; 60; 93 53,3; 60; 93 Overall dimensions Length, mm Width, mm Height, mm

3 Traction force, t Traction and speed performances truck, 90t (Cummins QSТ 30-C engine, 783 kw, GVW 163 t, КТЭ-90 electric transmission) truck, 90t (Cummins QST 30-C engine, 783 kw, GVW 169 t, hydromechanical transmission empty dump truck loaded dump truck % 30% 40 25% 20% 30 18% 16% 14% 20 12% 10% 8% 10 6% 4% Speed, km/h The above diagrams prove that there is an insignificant (up to 1 km/h) advantage of the dump truck with hydromechanical transmission on several intervals of the traction performance curve.

4 Traction force, t Traction and speed performances dump truck, 90t (Cummins QSТ 30-C engine 783 kw, GVW 163 t, КТЭ-90 electric drive) САТ 777F dump truck, 96t (САТ engine 746 kw, GVW 163,293 t, hydromechanical transmission 7+1) 60 empty dump truck loaded dump truck CAT 777F % 14% 20 12% 10% 8% 10 6% 4% Speed, km/h Similar picture is observed by comparison of the performances of and CAT 777F dump trucks.

5 In comparison of the traction and speed performances of dump truck (payload capacity 136t, Cummins QSK 45-C engine 1193 kw, General Electric GE150AC electric transmission) and CAT 785D dump truck (payload capacity 136t, CAT 3512C HD engine 1082 kw, six-stage hydromechanical transmission), the dump truck with electric drive demonstrates a speed advantage (up to 3 km/h on some intervals of the performance curve). However, this advantage is achieved not by means of the type of transmission used, but as a result of higher thrust-to-weight ratio. In case a less powerful engine is installed (e.g., Cummins KTA 38-C (895 kw) on dump truck), CAT 785D is at a speed advantage. Principal characteristics CAT 785D Payload capacity, kg Gross weight, kg Engine Cummins QSK 45-C Cat 3512C HD Engine power 1193 kw 1082 kw Transmission electric drive hydromechanical General Electric 6+1 Max speed, km/h Body volume, m³ heaped 2: ; 84; 134, ; 85 Overall dimensions Length, mm Width, mm Height, mm

6 Traction force, t Traction and speed performances dump truck, 136t (Cummins QSK-45C engine 1193 kw, GVW 244 t, GE electric transmission) САТ 785D dump truck, 136t (САТ 3512C HD engine 1082kW, GVW 249 t, hydromechanical transmission 6+1) 90 empty dump truck Loaded dump truck CAT 785D % 14% 30 12% 10% 20 8% 6% 10 4% Speed, km/h In this case the dump truck with electric transmission is at a speed advantage.

7 Also, lighter dump trucks do not demonstrate any speed advantage over heavier dump trucks. Thus, dump truck (payload capacity 136t, Cummins QSK-45 engine, maximum power kw, GE electric transmission), as a result of higher thrust-to-weight ratio, proves to be faster than CAT 777F dump truck (payload capacity 96t, maximum engine power kw, seven-stage hydromechanical transmission). At the same time, dump truck (payload capacity 130t, Cummins KTA 38-C engine, power 895 kw) appears to be slower. Principal characteristics CAT 777F Payload capacity, kg Gross weight, kg Engine Cummins KTA 38-C Cat Engine power 895 kw 746 kw Transmission electric drive hydromechanical 7+1 Max speed, km/h Body volume, m³ heaped 2: , ,1 Overall dimensions Length, mm Width, mm Height, mm

8 Traction force, t Traction and speed performances -7513, payload capacity 136t (Cummins QSK-45C engine 1193 kw, GVW 244 t, GE electric transmission) САТ 777F, payload capacity 96t (САТ engine 746 kw, Ga 163,293 t, hydromechanical transmission 7+1) empty dump truck empty dump truck loaded dump truck loaded dump truck CAT 777F % 14% 12% 10% 20 8% 6% 10 4% Speed, km/h Owing to a higher thrust-to-weight ratio, the heavier dump truck proves to be faster in this case.

9 Comparative calculation of the amount of transported mined rock The calculation is performed for the route of 1000 m. The slope on the whole route is assumed to be 6%. Maneuvering and loading time is taken as the same for all types of dump trucks and equal to 3,55 min. Unloading time is 1 min. The speed of an empty truck moving downhill is limited by the route and taken as 35 km/h. Therefore, the descent length for all types of dump trucks is equal to 1000 м : 35 km/h = 1,71 min. The total time for unloading, descending, maneuvering and loading is the same for all types of dump trucks and equal to 6,26 min. The speed of a full dump truck moving uphill at the slope of 6% is defined on the basis of the above diagrams of traction and speed performances and is different for each dump truck model. The ascent time is equal to the ratio of the route length to the speed of ascent. The total time of the operating cycle will be equal to the sum of maneuvering, loading, ascending, unloading and descending time. The number of cycles per working day (the day length is assumed to be 20 hours) is in inverse proportion to the cycle length. The amount of carried mined rock equals to the product of the number of cycles per day by the maximum payload capacity of the dump truck.

10 Comparative calculation data Cat785D Cat777F Engine Cat 3512C HD Cummins QSK 45-C KTA 38-C QST 30-C Engine power, kw Type of transmission HMT 6+1 electric drive electric drive HMT 7+1 electric drive HMT 6+1 Time for unloading,descending and loading, min. Ascending speed (slope 6%), km/h 20,75 23,40 6,26 17,80 22,20 21,00 21,00 Time of ascent, min. 2,89 2,56 3,37 2,70 2,86 2,86 Cycle length, min. 9,15 8,82 9,63 8,96 9,12 9,12 Number of cycles per hour 6,56 6,80 6,23 6,69 6,58 6,58 Working day length, hour Number of cycles per day 131,13 135, ,60 133,89 131,62 131,62 Percentage ratio to Max payload capacity, t Amount of mined rock per day, t Percentage ratio to Absolute values of the amount of carried mined rock depend on the characteristics of the route and they may vary considerably on different routes. Thus, the increase of the route length up to 2000 m will reduce this parameter by 50%, while the decrease of the slope from 6 down to 4% will provide a gain of approximately 10%. Meanwhile, in this case the proportions between the parameters of different dump trucks stay the same (deviations to the extent of 3%).

11 The calculation data confirm the statement that the type of transmission is not the factor determining speed advantage. Under equal conditions modern hydromechanical and electrical transmissions provide similar speed performances.

12 With the same payload capacity and speed, dump trucks with hydromechanical transmission and electric drive ensure the transportation of the same amount of mined rock.

13 The advantage of dump trucks with hydromechanical transmission is their capability to be operated on the routes with significant slopes (in the order of 22-36%). Electric drive Mechanical drive If the type of transmission is to be chosen for a dump truck which is supposed to be operated on the routes with slopes of up to 20%, it is better to judge not from the speed or amount of transported mined rock (which are almost the same), but from the ease of use and maintainability.

14 However, an electric drive is characterized with the following advantages: - Fixed gain in the transmission ensures smooth throttling and lightens the work of the operator; Mechanical drive Electric drive Benefit 1: 50% extended life of reduction gear Benefit 2: 30% extended life till overhaul of the engine

15 - less number of assembly units reduces the probability of failure, simplifies maintenance and reduces the volume of works; Mechanical drive - hydromechanical transmission - cardan drives - differential - half-axles - final drive components Electrical drive - alternator - control cabinet - power cable - motor wheels

16 - less number of mechanical components reduces the probability of failure due to wear, simplifies maintenance and reduces the volume of works; Mechanical drive Electric drive Less maintenance, easy to detect, easy to repair

17 - less quantity and range of filling fluids reduce operating costs and maintenance time Mechanical drive Electric drive 50% less oil and grease

18 Technical maintenance saving of electric trucks up to 38% Fuel consumption saving in compare with mechanical truck of the same capacity up to 15% Main braking unit electrodynamic braking with drive system brake pads saving - up to 5%

19 Also, it should be noted that less gross weight does not guarantee fast speed. Equal thrust-toweight ratio provides similar speed characteristics of dump trucks of different payload capacity. The calculation has demonstrated that the variation in speed between the compared models does not exceed 8%. At that, the heaviest dump truck has proved to be the fastest.

20 With the same number of operating cycles the heavier dump truck carries more. In accordance with the calculation, the dump trucks with the payload capacity of tons will transport 28-56% more of mined rock than the dump trucks with the payload capacity of tons.