Title: Dragline excavating machine with direct drive hoist and drag drums
Abstract: A dragline excavating machine includes a gearless direct drive AC drive motor for driving each of the hoist and the drag drums in the system. The gearless AC motor is driven using a digital system which receives AC power from the utility system rectifies the power using active front end circuits, and converts the resultant DC to a frequency controlled AC using an inverter circuit. The resultant AC signal is employed to drive the gearless AC motor, resulting in reduced harmonic distortion, unity or leading power factor, and increased efficiency, reduced operating costs, and reduced mean time between failure.
Patent Number: 7,024,805 Issued on 04/11/2006 to Onsager, et al.
| Inventors:
|
Onsager; Michael G. (Franklin, WI);
Gilmore; Carl D. (South Milwaukee, WI);
Koellner; Walter (Suwanee, GA)
|
| Assignee:
|
Bucyrus International, Inc. (South Milwaukee, WI)
|
| Appl. No.:
|
621644 |
| Filed:
|
July 17, 2003 |
| Current U.S. Class: |
37/396; 37/401; 701/50; 318/803 |
| Current Intern'l Class: |
E02F 3/50 (20060101) |
| Field of Search: |
37/394,395,396,397,398,399,400,401
701/50
318/3,11,12,13,803
|
References Cited [Referenced By]
U.S. Patent Documents
Other References
G.M. Brown, et al., Increased Productivity of AC Drives for Mining Excavators
and Haul Trucks, pp. 1-10, Oct. 9, 2000.
W. Koellner, et al., "AC Drive System with Active Front End (AFE) for Mining
Excavators," pp. 1-9, May 1, 2001.
Siemens, Active Front End—Simovert Masterdrives, pp. 1-10, Sep., 1997.
Siemens, A New Generation of Gearless Drives for the Ore Industry, Solutions
for Metals, Mining, and More, pp. 1-18, Mar., 1997.
|
Primary Examiner: Beach; Thomas A
Attorney, Agent or Firm: Quarles & Brady LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional patent application Ser.
No. 60/396,842 filed on Jul. 18, 2002 and entitled "Dragline Excavating Machine
with Direct Drive Hoist and Dragline Drums".
Claims
The invention claimed is:
1. An excavating machine comprising:
a bucket coupled to a hoist rope and to a drag rope;
a machinery housing, the machinery housing including:
a hoist drum coupled to the hoist rope;
a drag drum coupled to the drag rope;
a ring hoist motor coupled to the hoist drum to drive the hoist drum; and
a ring drag motor coupled to the drag drum to drive the drag drum, the drag drum
and the hoist drum working together to extend or retract the bucket; and
a drag variable speed AC drive system electrically connected to the ring drag
motor; and
a hoist variable speed AC drive system electrically connected to the ring hoist
motor, wherein the drag and hoist variable speed drives selectively rotate the
hoist and drag drums, respectively, to effect a digging operation;
wherein at least one of the hoist drum and the drag drum is coupled to a rotor
of the corresponding gearless ring hoist motor or gearless ring drag motor.
2. The excavating machine as defined in claim 1, further comprising a variable
speed AC drive electrically connected to the hoist motor and the drag motor to
drive the hoist and the drag motors.
3. The excavating machine as defined in claim 1, where the hoist motor and the
drag motor are each ring motors.
4. The excavating machine as defined in claim 2, wherein the variable speed AC
drive includes an active front end rectifier circuit.
5. The excavating machine as defined in claim 2, wherein the variable speed drive
includes an inverter circuit comprising at least one of an Insulated Gate Bipolar
Transistor (IGBT) switching circuit or an Integrated Commutating Gate Transistor
(IGCT) switching circuit or an Injection Enhanced Gate Transistor (IEGT) switching circuit.
6. The excavating machine as defined in claim 2, wherein the AC variable speed
drive comprises an AFE rectifier circuit for rectifying AC utility power to a DC
signal and an inverter circuit for converting the DC signal to a frequency controlled
signal for controlling the drag and hoist motors.
7. The excavating machine as defined in claim 6, wherein the AFE rectifier circuit
and the inverter circuit each use power transistors driven by a digital controller
to produce firing signals.
8. The excavating machine as defined in claim 7, wherein the power switching
devices are at least one of an IGBT device, an IGCT device, or an IEGT device.
9. The excavating machine as defined in claim 1, wherein the ring hoist motor
is integral with the hoist drum and the ring drag motor is integral with the drag drum.
10. An excavating machine, comprising:
a bucket;
at least one rope coupled to the bucket for raising and lowering the bucket;
a drum coupled to an end of the rope;
a ring motor having a rotor coupled to the drum; and
an inverter drive system electrically connected to the ring motor to rotate the
rotor in the ring motor, wherein as the rotor is rotated, the drum is rotated to
move the rope to effect an excavation operation.
11. The excavating machine as defined in claim 10, wherein the ring motor comprises
a ring-shaped stator circumventing the rotor.
12. The excavating machine as defined in claim 10, wherein the drum is configured
to hoist the bucket.
13. The excavating machine as defined in claim 10, further comprising a second
drum coupled to an end of a second rope and to the bucket, the second drum being
configured to drag the bucket toward the excavating machine.
14. The excavating machine as defined in claim 10, wherein the inverter drive
system is an active front end inverter.
15. The excavating machine as defined in claim 10, wherein the excavating machine
is a dragline.
16. The excavating machine as defined in claim 10, wherein the excavating machine
is a mining shovel.
17. The excavating machine as defined in claim 10, wherein the ring motor is
integrated into the drum.
18. An excavating machine, comprising:
a variable speed AC drive;
a ring motor, electrically connected to the variable speed AC drive;
a drum coupled to the rotor of the ring motor;
a rope, coupled at a first end to a digging element and at a second end to the drum;
wherein the variable speed drive selectively activates the ring motor to rotate
the rotor such that the drum rotates to move the rope and the digging element to
effect a digging operation.
19. The excavating machine as defined in claim 18, wherein the variable speed
drive comprise an inverter supply.
20. The excavating machine as defined in claim 18, wherein the variable speed
drive comprises an active front end inverter.
Description
BACKGROUND
The present invention is related to excavating machines, and more particularly
to excavating machines with improved motor control systems for controlling the
drag and hoist drums.
A dragline is an earth working or excavating machine used in mining operations
such as the extraction of coal, iron, copper or other minerals or materials. A
typical dragline excavating machine includes a machinery house mounted on a platform
supported for rotation. Extending from the machinery house is a boom supported
by cables or lines, and held at a desired angle of inclination by pendants extending
from the boom to a gantry mounted on top of the machinery house. A bucket is suspended
from the boom by hoist ropes wound on hoist drums in the machinery house, and can
be dragged toward the dragline excavating machine by coordinated motion of the
hoist ropes and drag ropes. The drag ropes are wound on drums also housed in the
machinery house. The machinery house includes drive systems for driving the hoist
and drag motors, "swing" motors for rotating the machinery house, and, for moving
or walking dragline excavating machines, drive systems for controlling the shoes
and walking mechanism or for controlling a crawling device.
At excavation sites, alternating current (AC) utility power lines are typically
provided to provide power for excavating equipment including the dragline excavating
machines used at the site. The hoist and drag drums in the dragline, however, are
very large, and draw a significant amount of power from the utility lines when
in use. The drive systems for driving the hoist and drag drums, therefore, must
be selected to provide sufficient power to drive the drums, and also must be selected
to limit the effects on the AC utility power system, including harmonic distortion
and power factor problems. Furthermore, to adequately provide excavation processes,
it is important to be able to drive the drums at a very low speed.
Because of these problems, the drag and hoist drums of typical dragline excavators
are operated by DC motors and associated motor-generator sets connected to the
AC power line. The motor-generator sets each include a large synchronous AC motor
driving DC generators, and are typically arranged in Ward-Leonard loop configurations
in which the large synchronous motors are capable of controlling power factor to
minimize power system effects.
While generally successful in powering dragline excavators with minimal effect
on the power supply, there are a number of disadvantages associated with the motor-generator
sets typically employed in these systems. First, because of the amount of force
required to drive the drums, multiple drive motors must be provided for each drum.
These motors require a significant amount of space in the machinery house, and
further require a significant amount of maintenance.
Furthermore, to drive the drums at a sufficiently low speed, the DC
drive motors are coupled to the drums through very large gear trains extending,
in some cases, over 25 feet. These large gear trains also require a significant
amount of space in the machinery housing, and further, are difficult to align accurately.
The production and maintenance of such gear trains, is, therefore, both difficult
and expensive, adding significantly to the cost and size of the resultant dragline excavator.
Because of these issues, since around 1980, more efficient AC drives have
also been applied in mining excavator applications. These AC drives, however, typically
use SCR rectifiers, and therefore suffer from high harmonic distortion and relatively
low power factor. Because these devices have a significant detrimental effect on
the AC utility power supply which can affect other devices using the utility power,
AC drives have not been applied successfully to large dragline excavators.
There remains a need, therefore, for an improved system for controlling the
drag and hoist drums in a dragline excavating machine, and particularly for an
improved system which reduces the number of parts, decreases maintenance requirements,
reduces the size of the equipment, provides increased machine productivity, reduces
energy consumption, and simplifies manufacturing.
SUMMARY OF THE INVENTION
The present invention provides an excavating machine comprising a bucket, and
at least one rope coupled to the bucket for raising and lowering the bucket. A
drum is coupled to an end of the rope, and a rotor of a ring motor is coupled directly
to the drum. An AC inverter drive system is electrically connected to the ring
motor to rotate the rotor in the ring motor. As the drum is rotated, the rope and
associated bucket are moved to provide an excavating operation.
In another aspect, the invention provides an excavating machine including a machinery
housing. A hoist drum in the machinery house is coupled to a hoist rope, and a
drag drum in the machinery house is coupled to the drag rope. A gearless ring hoist
motor is coupled directly to the hoist drum to drive the hoist drum, and a gearless
ring drag motor is coupled directly to the drag drum to drive the drag drum, such
that the drag drum and the hoist drum work together to extend or retract the bucket.
A variable speed AC drive system is coupled to each of the hoist and drag drums
to effect movement of bucket for an excavating operation.
The AC drive system can include active front end rectifiers for rectifying AC
input power and frequency-modulated inverter control for controlling the hoist
and drag motors. The active front end rectifiers provide a controllable power factor.
In yet another aspect, the present invention provides an excavating machine,
comprising
a variable speed AC drive with an active front end. A ring motor is electrically
coupled to the variable speed AC drive, and a drum is coupled to the rotor of the
ring motor. A rope is coupled at a first end to a digging element and at a second
end to the drum, wherein the variable speed drive selectively activates the ring
motor to rotate the rotor such that the drum rotates to move the rope and the digging
element to effect a digging operation.
These and other aspects of the invention will become apparent from the following
description. In the description, reference is made to the accompanying drawings
which form a part hereof, and in which there is shown a preferred embodiment of
the invention. Such embodiment does not necessarily represent the full scope of
the invention and reference is made therefore, to the claims herein for interpreting
the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a moving or walking dragline excavating machine.
FIG. 2 is a top view of the components provided on a floor of the machinery
house of FIG. 1.
FIG. 3
a is a top view of a hoist or drag drum coupled to a direct drive
ring motor.
FIG. 3
b is a side cutaway view of the hoist or drag drum of FIG. 3
a
taken along the line 3
b—3
b.
FIG. 3
c is a side cutaway view of an alternate embodiment of a hoist
or drag drum coupled to a direct drive ring motor.
FIG. 4 is a typical circuit diagram including both an active front end and inverter
circuit for driving the direct drive motors.
FIG. 5 is a circuit diagram of an Insulated Gate Bipolar Transistor (IGBT) Active
Front End (AFE) circuit.
FIG. 6 is a flow diagram illustrating a control circuit for the IGBT AFE circuit
of FIG. 5.
FIG. 7 is a block diagram of control circuit components and communication network
for a dragline mining system.
FIG. 8 is a block diagram of the IGBT AFE and Inverter circuits as controlled
by the controller of FIG. 7.
FIG. 9 is a top view of the components provided on a floor of the machinery
house of FIG. 1 in a second embodiment of the invention.
FIG. 10 is a block diagram of a control circuit for a dragline making system
as shown in FIG. 9.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the figures, and more particularly to FIG. 1, a portion
of a dragline excavating machine
1 is shown. The machine consists of a base
2, which rests upon the ground and supports machinery house
3. The
machinery house
3 has a boom
4 projecting upwardly from the lower
front of the house
3, the boom
4 having its foot connected to the
house by foot pins
5. The boom is held at the desired angle of inclination
by means of pendants
6 extending from the boom to a gantry
7 mounted
on top of the house
3. A bucket
19 is suspended by hoist ropes
8
which pass over sheaves
9 on the gantry legs to wind on hoist drums
10
in the house. The bucket is dragged toward the dragline excavating machine
1
by drag ropes
11 passing over fairleads
12 near the boom foot pins
5 and onto drag drums
13 in the machinery house
3. The house
3 is rotatably supported on a base by means of a roller circle (not shown).
The machine is mounted on a walking shoe or walking mechanism
15, which
allows the dragline excavating machine to be moved from place to place. The walking
mechanism
15 includes a shoe
16 that is driven internally by a drive
systems
17 including an internal motor and gear assembly
18, in a
conventional manner. Although the system will be described as a dragline excavating
machine throughout the specification, the technology described can also be provided
in other walking or moving excavating machines, and particularly in mining shovels.
Referring now to FIG. 2 a preferred embodiment of a machinery housing
3
constructed in accordance with the present invention is shown. Mounted to the floor
of the housing
3 are drive systems for each of the walking mechanisms
15,
the hoist drum
10, the drag drum
13, and associated swing motors
21. In this embodiment, the hoist
10 and drag drums
13 are
each connected to a single ring motor
22 and
26 driven by a variable
speed AC drive or "inverter",
38 and
40, respectively. An additional
inverter
45 is provided to operate the swing motors
21, and the walk
motors
18 controlling the walking mechanism
15. As the swing motors
21 and walk motors
18 are not operated at the same time, a single
inverter
45 can control each of these functions, thereby decreasing the
number parts used in the excavating machine. The inverters
38,
40,
and
45 are variable speed AC drives capable of driving motors at very low
speeds with minimal effect on power factor and minimal harmonic distortion in the
distribution system, and therefore allow for efficient, low speed control of the
motors, as described below. Although a single inverter
38,
40, and
45 is shown, a plurality of invertors can be used in each drive. Furthermore,
although a single drive motor is shown for each drum
10 and
13, two
motors could also be used, as described below.
Each of the hoist and drag motors
22 and
26 are gearless wrap-around
or ring motors. The gearless wrap-around or ring motors are very low speed AC synchronous
or asynchronous motors which, referring now also to FIG. 3, can be coupled directly
to the respective drum, thereby eliminating the need for gear trains to power the
drums
10 and
13. Similar gearless wraparound or ring motors have
been used in grinding mill, conveyor, and mine winding applications and are available
commercially, for example, from Siemens AG of Erlangen, Germany.
Referring now to FIGS. 3
a and
3b, a top view and a
cutaway view of a hoist or drag motor
22 or
26 are shown, respectively.
Referring first to FIG. 3
a, as described above, the hoist and drag motors
22 or
26 are AC wraparound or ring motors, and each comprise a spool
58 extending through the center of a ring-shaped section
59. Referring
now to FIG. 3
b, the spool
58 includes a rotor portion
60 which
is substantially centered in the ring-shaped section
59 and carries rotor
poles
62 for the case of a synchronous motor, or as squirrel cage in the
case of an induction motor, adjacent a stator winding
61 mounted in the
ring-shaped section
59. A drum portion
63, which can be either the
hoist drum
10 or drag drum
13 is coupled directly to the rotor portion
60, and rotates with the rotor portion
60, as described below. The
ring-shaped section
59 and associated rotor portion
60 are housed
in an outer housing
65 which is mounted to the floor of the machinery house
3. The spool
58 is further coupled through bearings
54 and
56 to vertical supports
50 and
52, which are also mounted
to the floor of the machinery housing
3. Referring now to FIG. 3
c,
in an alternative construction, the bearing
54 is mounted to an outer end
plate
55 of the motor, eliminating the vertical support
50 on that
end of the drum
10 or
13. Grooves
67 are provided in the drum
63 for receiving a rope for pulling a bucket or other mining implement.
Referring now FIG. 4, a block circuit diagram of the power system of the
dragline and inverters
38 and
40 is shown. Input power is provided
by an AC utility line
47 which is provided through a transformer
51
(FIGS. 2 and 4). The inverters
38 and
40 are very low speed, variable
speed AC drives capable of operating in a range of twenty hertz or less. These
variable speed drives preferably include active front end (AFE) rectifiers
42
for converting the AC utility power supply
47 to a direct current (DC) voltage
43, and an inverter circuit
44 for converting the DC voltage
43
to a frequency-controlled AC signal
49 for driving the motor
22 or
26. Referring now to FIG. 5, as noted above, these drives typically utilize
power switching devices
69 such as IGBT (insulated gate bipolar transistor)
or IGCT (integrated gate commutated transistors) or IEGT (injection enhanced gate
transistor) technology both in the AFE rectifier
42 and in the inverters
44. In the AFE rectifier
42, this technology allows the drive to
control power factors appropriately for use in the dragline while generating a
relatively low level of harmonics. In the inverter
44, this technology provides
a variable voltage/variable frequency source to power and control the wraparound
or ring motors
22 and
26 efficiently and at very low speeds with
significant resolution.
Referring now to FIGS. 6 and 7, a closed loop control is used to regulate
the output voltage VDC of each of the AFE circuits
42 by maintaining the
balance of active power through the circuit using feedback loops
70 and
71 to control the active current I
d 72 and the reactive
current I
q 74. A vector modulator
76 is used to generate
the firing pulses for the power transistors in the AFE circuit
42 and, as
a result of this control, the AFE circuit
42 controls the power factor without
additional capacitors or passive filters. The AFE is preferably designed to operate
with power factor PF=1. If required, a leading power factor of up to 0.8 leading
can be adjusted. Referring now also to FIG. 8, the control of the AFE rectification
and inverter circuits
44 can be provided by a central controller
46
which provides firing signals for all of the IGBT circuits and which can also be
tied through communications links to various other operating stations in the machine
to provide maintenance and other functions. Although variable speed drives as described
above can be built specifically for the application, suitable variable speed AC
drives are commercially available for instance from Siemens AG of Erlangen Germany,
sold under trade names such as Simovert® Masterdrives, Simovert® ML,
Transvektor® controls, and other brand names. Although commercially available,
typically, these drives are built and sized for a specific application.
Referring now to FIGS. 9 and 10, a second embodiment of a floor of a machinery
house
3 and associated control circuitry constructed in accordance with
the present invention is shown, with components mounted providing drive systems
for each of the walking mechanisms
15, the hoist drums
10 and drag
drums
13, and associated swing motors. Here, each of the drums
10
and
13 are driven by one or two motors. The hoist drums
10 are driven
by first and second hoist motors
20 and
22, while the drag drums
13 are driven by first and second drag motors
24 and
26. Each
of the inverters
38 and
40 include first and second AFE rectifiers
42 and first and second inverter circuits
44, providing one AFE rectifier
42 and one inverter circuit
44 for each motor
20,
22,
24, and
16. Here, motor-generator sets are provided for driving the
swing motors
21 and the crawler motors
18. Although a machinery house
3 as shown in FIG. 9 could be provided in a new excavating machine, this
embodiment illustrates a method of retrofitting an existing excavating machine
with hoist and drag motors
22 and
26 and inverters
38 and
40 as described above. Although the motor-generator sets could be removed
and replaced with an inverter
45 to drive the swing motors
21 and
walk motors
18, here the motor-generator sets have been retained to limit
the cost of a retrofit. Various other methods of retrofitting existing dragline
systems will be apparent, and those configurations can be provided in both one
and two motor drive configurations.
Referring again to FIG. 2, in operation, the inverters
38 and
40
receive power from the utility line
47 through a transformer
51,
and convert the power to a voltage and frequency controlled signal to drive the
ring motors
22 and
26. As the motors
22 and
26 are
rotated, the rotor portions
60 directly rotate the hoist drum
10
and drag drum
13, respectively. The present invention therefore provides
a gearless drive for directly driving both the hoist drum
10 and drag drum
13, eliminating the large and expensive gear trains found in prior art dragline
or other excavating machines. The elimination of the gear trains found in prior
art devices significantly reduces the size and complexity of the machinery house,
reduces maintenance functions such as lubrication, and simplifies the manufacturing
of the dragline. Furthermore, the construction of the present invention significantly
reduces the mean time between failure, and significantly reduces the cost of replacement
parts for gears and other parts subject to wear during use.
Furthermore, the use of the variable speed AC drive system with active
front end reduces power factor and harmonic distortion issues associated with prior
art systems, and further provides a more efficient control system which is more
reliable and has a longer mean time between failure. The power transistor switching
circuits, furthermore, have a high overload capacity which further eliminates the
need for protective circuits for the rectifiers and inverters in the drive system.
The drive system can operate at a unity (or better) power factor and less than
8% total harmonic distortion. Furthermore, total efficiency of the system has been
shown to be up to 20% higher than that of prior art DC drives.
Additionally, the present invention significantly reduces the number
of (and preferably completely eliminates) DC motor-generator sets, thereby reducing
the number of components required in the dragline excavating machine, reducing
maintenance, mean time between failure, manufacturing complexity, the number of
spare parts required for maintenance, and the overall size of the drive system
for the dragline. The reduction in motors and gear train components, in fact, allows
the system to be provided in the same deck footprint as prior art systems despite
larger motor configurations. As the wraparound gearless or ring motors used in
the system do not use the brushes and commutators found in DC systems, the AC motor
systems further require less maintenance than prior art DC systems.
Furthermore, the digital control system employed in the dragline excavating
machine can be connected to an overall control system, providing easy access to
maintenance and operational information, and allowing the dragline system to be
tied to other components in an excavating operation to provide overall control
of an excavating operation.
Additionally, replacing the gearing and DC motor-generator sets with
gearless ring motors and associated AC variable speed drives improves the speed
and resolution of bucket movements resulting in increased productivity. Use of
the gearless drive system of the present invention results in reduced bucket filling
times, higher hoisting speeds, and greater efficiency. Furthermore, these productivity
increases can be achieved while reducing energy consumption.
Although the system has been described with reference to a dragline excavating
machine, the described technology could be applied to other walking and moving
excavating machines as well. For example, the system described can be provided
also in a mining shovel application.
The invention has been described in detail with particular reference to certain
preferred embodiments thereof, but it will be understood that variations and modifications
can be effected within the spirit and scope of the invention.
*
