Mining vehicle and method for its energy supply

A mining vehicle and a method for an energy supply of the mining vehicle is disclosed. The mining vehicle includes at least one mining work device, at least one AC electric motor for powering the at least one mining work device, and an auxiliary energy source. The mining vehicle further includes a power electronics device that is used for supplying reactive current and for charging or discharging the auxiliary energy source. The amount of the reactive current supplied by the power electronics device and the amount of the effective charging current for charging or discharging the auxiliary energy source are controlled such that the maximum value for the current of the supply cable and the maximum value for the current of the power electronics device are not exceeded.

RELATED APPLICATION DATA

This application claims priority under 35 U.S.C. § 119 to EP Patent Application No. 14199556.3, filed on Dec. 22, 2014, which the entirety thereof is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a mining vehicle and to a method for energy supply of a mining vehicle.

BACKGROUND

In mines, rock drilling rigs and other mining vehicles are used to perform operations according to work cycles of mining work devices at pre-planned work sites. After the necessary tasks according to a work cycle, such as borehole drilling, have been performed, the mining vehicle is moved to the next work site and a new work cycle is started. In underground mines in particular, mining vehicles are generally used, the driving energy for operations according to the work cycles being electricity from an electrical network of the mine. By contrast, transfer drives between work sites are performed by driving energy obtained by using a combustion engine, typically a diesel engine, whereby electric cables or the like do not restrict the transfer drives. However, exhaust gases and noise from a combustion engine cause problems in mines. In addition, a combustion engine occupies a lot of space on the carriage of the vehicle and necessitates regular maintenance. A combustion engine also has adverse effects on fire safety in the mine, since it has hot surfaces and it is also necessary to store and handle flammable fuel in the vehicle and the mine.

Mining vehicles that are continuously connected to the electrical network of the mine are also used in mines. These mining vehicles have an electric motor, and typically one with a constant rotation speed. Power required by the work phase may then be adjusted with hydraulic components, and the electric motor obtains the electric current and load power defined by the energy consumption of the work phase from the electrical network of the mine. Further, the movement of the mining vehicle is then typically bound to the electrical network or at least to a cable connected thereto, the cable being coiled in the mining vehicle or at the fixed electrical network.

SUMMARY

It is an aspect of the present disclosure to provide a new type of mining vehicle and a method for its energy supply.

In the presented solution, a mining vehicle includes at least one mining work device, at least one AC electric motor for powering the at least one mining work device, and an auxiliary energy source. The mining vehicle further includes a power electronics device for charging the auxiliary energy source, and a connecting device connectable to a supply cable for supplying electric current to the mining vehicle from a supply grid. A maximum value for the current of the supply cable is determined.

A current of the supply cable is may be an effective current of the at least one electric motor, a reactive current of the at least one electric motor and an effective charging current of the power electronics device used for charging the auxiliary energy source. The power electronics device is used for supplying reactive current and for charging or discharging the auxiliary energy source. A maximum value for the current of the power electronics device is determined. The current of the power electronics device may include the reactive current supplied by the power electronics device and the effective charging current for charging or discharging the auxiliary energy source. The maximum value for the current of the power electronics device is smaller than the sum of the maximum value of the effective charging current for charging or discharging the auxiliary energy source and the maximum value of the reactive current the power electronics device is able to supply. The amount of the reactive current supplied by the power electronics device and the amount of the effective charging current for charging or discharging the auxiliary energy source are controlled such that the maximum value for the current of the supply cable and the maximum value for the current of the power electronics device are not exceeded. Thereby the supply cable and the power electronics device need not be dimensioned to be large. However, the auxiliary energy source may be charged effectively without limiting full power drilling, for example.

According to an embodiment, the need for charging is determined. If there is no need for charging, as much reactive current as needed and/or possible is supplied by the power electronics device. The reactive current is thus compensated in a simple manner and cost effectively.

If there is a need for charging it is determined whether the needed charging current would cause an overshoot of the maximum value for the current of the power electronics device. If an overshoot is caused, it is determined if it is possible to reduce the reactive current compensation. If it is possible to reduce the reactive current compensation, it is reduced and charging is then performed. Charging is thus performed without causing an overshoot, yet ensuring a sufficient charge in the auxiliary energy source.

According to a further embodiment, a temperature of the electric motor is measured. If the temperature is low enough, it is possible to reduce the reactive current compensation. Thus, in the beginning of the working cycle, for example, the charging may be performed without causing an overshoot and simultaneously supplying a large amount of power from the supply grid to the mining work device, for example.

The mining vehicle may have one or more of the following mining work devices: a rock drilling machine, bolting machine, shotcreting device, scaling device, injection device, blast-hole charger, loader, dumper, measuring device, or drilling, sealing and propellant feeding equipment used in small-charge excavation. The rock drilling machine may be a face drilling device or a device used in production hole drilling, that is a long-hole drilling device that drills boreholes in a fan shape. The mining work device may be an actuator used in handling undetached rock and may perform several consecutive operations according to a given work cycle. Typically, several similar operations are performed with the mining work device at one work site. These operations may be defined in an excavation plan, such as a drilling plan, charging plan, or a corresponding mining plan. The mining work device is usually arranged on a boom with which the device is moved during the work cycle. On the other hand, the mining work device may be arranged on a corresponding support or support structure in a mining vehicle, supporting the device during its work cycle.

The foregoing summary, as well as the following detailed description of the embodiments, will be better understood when read in conjunction with the appended drawings. It should be understood that the embodiments depicted are not limited to the precise arrangements and instrumentalities shown.

In the figures, some embodiments of the present disclosure are shown simplified for the sake of clarity. Similar parts are marked with the same reference numbers in the figures.

DETAILED DESCRIPTION

FIG. 1shows a rock drilling rig, which is one example of a mining vehicle1equipped with one or more mining work devices2. The rock drilling rig includes a carriage3that may be moved by drive equipment4. The drive equipment4includes one or more drive motors5and one or more power transmission means6for transmitting drive power to one or more wheels7. The drive power transmission may include a mechanical gear system and mechanical power transmission members or, alternatively, the drive power transmission may be hydraulic or electric. There may be one or more booms8arranged on the carriage3, and the boom may be equipped with a mining work device2.

In the embodiment shown inFIG. 1, the first boom8ais a drilling boom, at the outermost end of which there is a rock drilling unit9comprising a feed beam10, along which a rock drilling machine11can be moved by a feed device12. The rock drilling machine11may include a percussion device13for generating impact pulses on a tool and a rotating device15for rotating the tool14around its longitudinal axis. There may be several of these drilling booms8ain the rock drilling rig. By way of example, a second boom8bis shown to include a bolting device16, with which rock bolts can be arranged in pre-drilled boreholes to support the excavated rock cavern. In the embodiment ofFIG. 1, a third boom8cis equipped with a measuring device17for measuring drilled boreholes. Other alternative mining work devices2include injection devices used in feeding sealing material into rock, shotcrete processing devices, scaling equipment, devices used in small-charge excavation, and devices for feeding explosives.

The mining vehicle1is run in accordance with the excavation plan of the mine18, or a corresponding pre-drafted plan, to a work site19where the mining work device2performs operations according to the work cycle, which takes a relatively long time. For instance, the work cycle of a rock drilling machine may include drilling several boreholes defined in the drilling plan at the work site19. Further, drilling of each borehole typically consists of several work phases, such as collaring, actual drilling, changing extension rods and drill bits, and dismantling extension rod equipment after drilling. Performing a drilling work cycle at the work site19may take several hours, sometimes even an entire work shift. Correspondingly, charging, bolting, measuring, and injecting are often quite time-consuming operations. Generally, the use of a mining work device2has to do with drilling a borehole or further processing a finished hole. This then means handling undetached rock.

FIG. 1further shows that the mine18has an electrical network or a supply grid20that may be fixedly constructed or it may consist of a modifiable network. The supply grid20is typically a three-phase alternating current network. When the mining vehicle1is at the work site19, its mining work device2, hydraulic system and any necessary auxiliary systems are mainly driven by electrical energy obtained from the supply grid20. The mining vehicle1may be connected to the supply grid20with one or more supply cables21. The supply cable21may be arranged on a reel22and it may be equipped with a suitable connector23that may be connected to the supply terminal of the electrical network20. Alternatively, the reel22and the cable21may be arranged in the mine18, and the supply cable21is connected to the mining vehicle1. The mining vehicle1includes an electric motor26, which is connected via a connecting device24to the supply grid20. In the mining vehicle1, hydraulic pressure is produced by a hydraulic pump27. The hydraulic pump is rotated by the electric motor.

The mining vehicle1is equipped with a connecting device24, through which the electricity supplied from the supply grid20is connected to different devices of the mining vehicle1. The mining vehicle1is also equipped with at least one auxiliary energy source25. The auxiliary energy source25may be a battery, a supercapacitor or their combination, for example, or any other suitable energy source that may be charged.

FIG. 2shows some parts of the mining vehicle schematically. As shown, the electric motor26is connected to the supply grid20. The electric motor26rotates the hydraulic pump27. The electric motor26also includes a shaft28. When electric energy is supplied from the supply grid20to the electric motor26, the rotor of the electric motor is rotated. The shaft28is connected to the rotor of the electric motor26, and thereby the electric energy from the supply grid20rotates the shaft28.

The shaft28is arranged/connected to rotate the hydraulic pump27. When rotated the hydraulic pump27produces hydraulic pressure to the hydraulic system of the mining vehicle. The hydraulic system of the mining vehicle is denoted by reference numeral29.

The hydraulic pressure in the hydraulic system29is used for supplying power to the mining work devices2, for example. The hydraulic pressure may also be used for driving a hydraulic system of the driving equipment, such as steering and braking, for example.

The energy source25is connected via an inverter30to the supply grid20. The inverter30is a power electronics device that is used for charging the auxiliary energy source25. The inverter30may also be used for discharging the auxiliary energy source25. Discharging the auxiliary energy source means that energy from the auxiliary energy source25is supplied via the inverter30for further use in the mining vehicle or even to the supply grid.

The auxiliary energy source25may be connected to the drive motor5via the inverter30. Energy from the auxiliary energy source25may thus be used for the transfer drive of the mining vehicle1, for example.

During full power drilling, for example, it is also possible to supply energy from the auxiliary energy source25to the mining work device2, whereby a boost mode is achieved. In the boost mode, energy is supplied to the mining work device from the supply grid20and from the energy source25. During the boost mode, the load of the electric motor26to the supply grid20may thus be decreased by simultaneously supplying energy to the mining work device from the energy source25.

It is also possible to supply energy to the mining work device2from the energy source25only. Thus, so-called low power drilling could be achieved even if the supply grid20were not able to supply energy, for example.

The inverter30is connected to a bus bar31. The electric motor26is also connected to the bus bar31. Other electric motors, such as a water pump and a compressor, may also be connected to the bus bar31.

A DC bus bar32may be provided between the inverter30and the auxiliary energy source25. Other components, such as a cabin heater, may also be connected to the DC bus bar32.

The mining vehicle may also include a compensation device33. The compensation device33is connected to the bus bar31. The compensation device33may be a fixed compensation capacitor or a controllable compensation device.

The vehicle may also include a power factor meter34. The power factor meter34may also be connected to the bus bar31. Further, the vehicle includes a control unit35. Measuring results are guided to the control unit35and the control unit35controls the devices of the vehicle.

The AC electric motor26is a cage induction motor that requires a magnetisation current which is reactive current. If this reactive current is not compensated for at the motor the reactive current oscillates between the motor and the supply grid, thus loading the supply cable21. The reactive current supplied via the supply cable21decreases the supply voltage. Low supply voltage causes overheating of the electric motors, starting problems, and dangerous situations regarding the short-circuit protection. Compensating for the reactive current raises the supply voltage, which in turn decreases the current of the electric motors and minimizes their warming.

The power factor meter34measures how much compensation is needed for compensating for the reactive current. The control unit35may control the compensation device33to supply the reactive current.

Referring toFIG. 3, the inverter30is such that, in addition to charging or discharging the auxiliary energy source25, it is capable of supplying a reactive current. If the compensation device33cannot supply enough reactive current, the control unit35may control the inverter30to supply reactive current. Supplying reactive current by the inverter30does not substantially consume the energy of the auxiliary energy source25. The only energy consumed is caused by the losses of the inverter. Therefore it is advantageous to supply by the inverter30as much reactive current as possible and/or needed while the inverter30is not used for charging or discharging the auxiliary energy source25, for example, or whenever possible. Naturally, if the need for reactive current is less than the maximum value of the reactive current the inverter is able to supply the inverter supplies only the needed amount. On the other hand, if the need for reactive current is equal to or higher than the maximum value of the reactive current the inverter is able to supply the inverter supplies reactive current as much as possible.

A maximum value for the current of the inverter30is, however, determined. The current of the inverter30may include the reactive current supplied by the inverter and the effective charging current for charging or discharging the auxiliary energy source25. Thus, the current of the inverter includes one or more of the following currents: the reactive current supplied by the inverter and the effective charging current charging or discharging the auxiliary energy source. For the inverter30not to be dimensioned too high the maximum value for the current of the inverter30is smaller than the sum of the maximum value of the effective charging current for charging or discharging the auxiliary energy source and the maximum value of the reactive current the inverter30is able to supply. Also a maximum value for the current of the supply cable21is determined. A current of the supply cable may include the effective current of the electric motor26, the reactive current of the electric motor26and the effective charging current of the inverter30used for charging the auxiliary energy source. Thus, the current of the supply cable may include one or more of the following currents: the effective current of the electric motor, the reactive current of the electric motor and the effective charging current of the inverter used for charging the auxiliary energy source.

The inverter30is used for supplying reactive current and for charging or discharging the auxiliary energy source25but only such that the maximum value for the current of the supply cable21is not exceeded. Thus, during full power drilling, for example, the inverter30is not used for charging the auxiliary energy source25. The inverter30is, however, used for supplying as much reactive current as possible and/or needed. Furthermore, the inverter30is controlled such that the maximum value for the current of the inverter30is not exceeded. Thus, before charging, it is determined if the needed charging current would cause an overshoot of the maximum value for the current of the inverter, and, if it would, no charging would be performed. If, however, it is possible to reduce the reactive current compensation such that the inverter30does not supply so much reactive current, the reactive current compensation is reduced. Charging can then be performed without causing an overshoot of the maximum value for the current of the inverter30. The reactive current compensation may be reduced if no full power drilling is simultaneously performed, for instance. During such a situation the supply grid20may supply reactive current via the supply cable21—provided that the maximum value for the current of the supply cable21is not exceeded, naturally.

An excavation plan of the mine may also be used for scheduling the charging. The charging is thus scheduled to be performed between full power drilling sequences, for example.

A temperature of the electric motor26may also be measured by a temperature meter36, for example. In the beginning of the drilling sequence the electric motor26is still cold. When the electric motor26is cold there is not much need for reactive current compensation. Thus, on the basis of the temperature of the electric motor, the possibility for reducing reactive current compensation may be determined. The inverter30may thus be used for charging because there is no need for the inverter30to supply reactive current which would cause an overshoot of the maximum value for the current of the inverter30.

Instead of the inverter30the power electronics device may also be a motor drive mechanism or a charging device, for example.

A separate drive motor5is not necessarily needed but the electric motor26may produce the drive power needed. In that case the power transmission means6are connected to the shaft28of the electric motor26. The mining vehicle1may include one or more electric motors26.

The mining vehicle1may also include one or more hydraulic pumps27. The electric motor26may rotate one or more hydraulic pumps27, or each hydraulic motor27may include an electric motor of its own.

It should be mentioned that, in this specification, a mine refers to underground mines and opencast mines. Further, the method and the mining vehicle may be used at contract work sites, for example when excavating different rock facilities. Therefore, a contract work site may also be considered a type of mine. At contract work sites, an external electrical network may be modifiable, such as an aggregate on a movable carriage.

In some cases, the features described in this specification may be used as such, regardless of other features. On the other hand, the features described in this specification may also be combined to provide various combinations as necessary.

It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways.

Although the present embodiment(s) has been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims.