Note: Descriptions are shown in the official language in which they were submitted.
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PERMANENT MAGNET DIRECT DRIVE DRAWWORKS
FIELD OF THE INVENTION
[0001] The present invention relates to oil field equipment. More
particularly, the present invention
the relates to a drawworks used in oil and gas drilling and production. More
particularly, the present
invention relates to a drawworks having a permanent magnet motor.
BACKGROUND OF THE INVENTION
[0002] A drawworks is a common piece of oil field equipment that is used in
oil and gas drilling and
production. A drawworks is typically mounted near an oil rig. A common
function of a drawworks
is to raise and lower drillpipe and casing out of and into a wellbore. A
drawworks can be referred
to as a hoist or a winch. There are many different sizes of drawworks that are
used in the drawworks
in the drilling and mining industries. The sizes of the drawworks are
reflected in the power ratings
for such drawworks. These drawworks share similar operating modes and similar
equipment.
[0003] Drawworks are used in the hoisting and lowering of loads, such as drill
pipe, when inserting
and extracting the drill pipe into out of the open well. The extraction of the
pipe can require
extracting in excess of 30,000 feet of pipe in order to change drill bits or
tooling during the drilling
operation. During typical oil well drilling operations, the drill pipe is
often hoisted and lowered
many times during these operations.
[0004] During mining operations, similar equipment is used in hoisting coal,
overburden material,
sand and gravel, phosphates and other minerals. These are just a few of the
typical operations in
which the drawworks are utilized. In mining operations, a bucket is often
lowered for the purposes
of allowing the loading of the bucket with the materials. After the bucket is
loaded, the drawworks
are used so as to hoist the loaded bucket to an elevation whereby the bucket
is unloaded at a location
above the earth.
[0005] FIGURE 1 shows a conventional drilling rig 10 that utilizes a prior art
drawworks 26. The
drawworks 26 is mounted to the rig floor 12 within the interior of the oil
derrick 11. The drawworks
26 has a wire line 24 extending around the pulley 25 so as to raise and lower
drill pipe 14 from and
to the wellbore 16. The pulley 25 is also known as a crown block. The wellbore
16 is formed in the
earth 50. The drill pipe 14 can be a drillstring that is a series of drill
pipes extending within the
wellbore 16 in the earth 15. Individual drill pipe 14 is connected to the
drillstring at threaded joint
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17. Portions of the drillstring may have stabilizer portions that include
stabilizer elements 18 that
extend helically along the outer surface of the pipe 14 so as to engage the
wall of the wellbore 16 in
a manner that centers the pipe 14 therein.
[0006] The drawworks 26 extends and retracts wire line 24 over the pulley 25
that is mounted on the
oil derrick 11 so as to raise and lower the drilling unit 19 that holds the
drillpipe 14. The line 24 is
connected to traveling block 23. The traveling block 23 is suspended and moved
upwardly and
downwardly by the line 24 which is extended and retracted by the drawworks 26.
The traveling
block 23 is connected to the drilling unit 19. The drilling unit 19 has a
swivel 22 at its upper end
to which drilling fluid is introduced into the drill pipe 14, and by which the
drilling unit 19 is
suspended from the traveling block 23. The drilling unit 19, pipe handler 21,
and the associated
connected parts move vertically along axis 20. The vertical movement is guided
by two vertical
guide rails, or tracks, 27 that are rigidly attached to the derrick 11. The
drilling unit 19 is attached
to a carriage 28. The carriage 28 has rollers that engage the rails 27. The
rails 27 guide the carriage
28 for vertical movement upwardly and downwardly along the rails 27 parallel
to vertical axis 20.
The drill pipe 14 is inserted into and removed from the wellbore 16 through
the wellhead 13.
[0007] The drawworks 26 typically has a hollow drum, a shaft that connects the
drum to a motor,
a transmission positioned between the motor and the drum, and a braking system
for slowing the
rotation of the drum. The drawworks 26 is mounted on the floor 12 of the
drilling rig 10. The
longitudinal axis of the drum and shaft is parallel to the drill floor 12.
Typical motors used on the
drawworks 26 are AC electric motors, DC electric motors, and diesel combustion
engines. Power
is typically transmitted from the motor to the shaft by a chain transmission
mechanism or a gear
transmission mechanism. The braking system can use a variety of techniques for
braking the drum.
The braking system can use disc brakes, band brakes, water-cooled brakes, or
electric brakes. As
the line 24 is retracted by the drawworks 26, the line 24 is wrapped around
the drum of the
drawworks 26. The wrapping of the line 24 around the drawworks 26 is similar
to wrapping a thread
around a spool.
[0008] The use of a transmission causes many problems commonly associated with
the typical
drawworks. A transmission is costly, adds weight to the drawworks, and needs
periodic repair.
Maintenance of a transmission can be costly especially in the event of a total
failure of the
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transmission. Power is also lost with the use of a transmission due to
frictional forces inherent in the
use of transmissions. Typical drawworks 26 also use large amounts of energy
for changing direction
of rotation of the drawworks 26. Thus, there is a need for a simple design of
a drawworks that is
lighter, easier to maintain, uses less energy, and is more energy efficient.
[0009] In the past, various patents have issued relating to drawworks. For
example, U.S. Patent No.
6,182,945, issued on February 6, 2001 to Dyer, et al., discloses a fully
redundant drawworks with
two complete and totally independent systems for controlling and powering the
drum and the drum
shaft of the drawworks. Each system has at least one power source, a power
transmission, and a
coupler connected to the power source and to the transmission and to the drum
shaft. Each system
has a braking system, such as disc brakes, band brakes, electric brakes, or
water- cooled brakes. In
the event that any component of either system fails, the fully redundant
drawworks has the ability
to raise drillpipe from a wellbore so as to avoid the risk of a "stuck" drill
pipe.
[0010] U.S. Patent No. 4,226,311, issued on October 7, 1980 to Johnson et al.,
discloses a disc-type
brake apparatus adapted for installation in combination with the drawworks of
a wellbore drilling
operation. The apparatus automatically senses any reverse torque situation in
the drill pipe and
quickly sets the brake for precluding transmission of any reverse torque to
the rotary table device
clutch mechanism therefor.
[0011] U.S. Patent No. 3,653,636, issued on April 4, 1972 to Burrell,
discloses a reversible hydraulic
motor and a high-pressure/low-pressure hydraulic reservoir system that are
used to counterbalance
the weight of a drillstring or other well equipment suspended from a line
wound on a drawworks
positioned on a floating vessel. A load cell controls the torque output and
the direction of the output
drive of the hydraulic motor. Upon downward movement of the floating vessel,
high pressure
hydraulic fluid from an accumulator moves through the hydraulic motor into a
low pressure
hydraulic fluid reservoir to provide increased torque to the drawworks as the
drawworks spools a
wire line upward. Upon an upward movement of the floating vessel, the
hydraulic motor reverses
so as to move low pressure fluid from the low pressure reservoir to the high
pressure accumulator.
This decreases torque and reverses direction to the drawworks as the drawworks
extends the line.
[0012] U.S. Patent Publication No. 2008/0116432, published on May 22, 2008 to
Folk et al.,
discloses a winch that includes an electric motor having a fixed stator, and a
cylindrical rotor which
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rotates about the stator. A drum is affixed to the rotor and carries a cable
which is wound or
unwound by the winch. The winch may be a drawworks for an oil rig. The
electric motor can be
a permanent magnet electric motor. A bearing mechanism is positioned between
the motor stator
and the motor rotor.
[0013] U.S. Patent No. 3,211,803, issued to Pryor et al., discloses a
generator-feed electric drive for
a drawworks that has a drawworks, electric motors, a driving connection
between the motors and the
drawworks, a generator, an electrical connection to the generator and the
motors for supplying
electricity to the motors, an engine, and a connection between the engine and
the generator for
supplying power to the generator. The electric motors have a total power
absorption capacity that
is substantially larger than the power output capacity of the engine, whereby
the torque available to
drive the drawworks is substantially greater than would be available from
motors having a total
power absorption capacity equal to the power output capacity of the engine.
[0014] U.S. Patent No. 4,438,904, issued on March 27, 1984 to White, discloses
a drawworks that
has a drilling platform supporting the drawwork, a cable-drum shaft rotatably
supporting the cable
drum between two upright support-wall members, an input shaft, a driving
mechanism for driving
the input shaft in rotation, a clutch-controlled chain sprocket and chain
transmission for causing
rotation of the drum shaft and the cable drum at any of multiple speeds in
response to rotations of
the input shaft, and a controller disposed outside of one of the support-wall
members. The drum
shaft has an extension beyond one of the support-wall members. A single
outboard brake is fixed
to the drum-shaft extension.
[0015] U.S. Patent No. 6,029,951, issued on February 29, 2000 to Guggari,
discloses a system and
method for the use of a drawworks where the drawworks has a rotatable drum on
which a line is
wound. The drawworks and the line are used for facilitating a movement of a
load suspended on the
line. A drawworks-control system monitors and controls the drawworks. A brake
arrangement is
connected to the rotatable drum for limiting the rotation of the rotatable
drum. An electrical motor
is connected to the rotatable drum for driving the rotatable drum. The
drawworks control system
provides a signal that is representative of the calculated torque value of the
electrical motor wherein
pre-torquing is generated in the electrical motor in response to the signal.
Control of the rotation of
the rotatable drum is transferred from the brake arrangement to the electrical
motor when the
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electrical motor pre-torquing level is substantially equal to the calculated
torque value.
[0016] U.S. Patent No. 4,046,355, issued on September 6, 1977 to Martin,
discloses a control
apparatus for use with a drawworks assembly that has a work piece suspended
from, and applying
tension to, a cable. One end of the cable is wound on a drum. The rotation of
the cable is controlled
by a power brake mechanism. The control apparatus has a cable tension sensor
that produces a
tension signal proportional to the tension in the cable. A pulse generator
produces a pulsed control
signal. A brake control applies the tension signal to the power brake
mechanism in response to the
control signal.
[0017] U.S. Patent Application No. 60/726,077, filed on October 13, 2005 by
the present inventor,
discloses a drawworks for drilling and mining operations. The drawworks has a
wire rope drum
which is driven by at least one AC motor. A drive shaft couples a brake with
the wire rope drum.
The motor is operated from a utility power supply. The drawworks has a
flywheel system that stores
energy while braking the rotation of the rope wire drum of the drawworks.
Energy stored in the
flywheel is used to begin another rotation of the wire rope drum.
[0018] It is an object of the present invention to provide a direct-drive
drawworks.
[0019] It is another object of the present invention to provide a drawworks
that requires no gearing
mechanism.
[0020] It is another object of the present invention to provide a drawworks
that has a very high
power density.
[0021] It is another object of the present invention to provide a drawworks
that is relatively light
weight.
[0022] It is still another object of the present invention to provide a
drawworks that can be easily
transported on conventional road systems.
[0023] It is another object of the present invention to provide a drawworks
which has minimal
assembly requirements in the oil field.
[0024] It is another object of the present invention to provide a drawworks
that is easily replaceable
in the oil field.
[0025] It is still another object of the present invention to provide a
drawworks that has reduced
inertial effects.
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[0026] It is another object of the present invention to provide a drawworks
that reduces costs of
operating and repair.
[0027] These and other objects and advantages of the present invention will
become apparent
from a reading of the attached specification and appended claims.
BRIEF SUMMARY OF THE INVENTION
[0028] In accordance with one disclosed aspect there is provided a direct
drive drawworks
including a peinianent magnet motor. The permanent magnet motor includes a
housing, a stator
positioned in the housing, and a rotor cooperative with the stator, the rotor
having a drive plate
affixed thereto. The direct drive drawworks also includes a shaft directly
connected to the drive
plate and extending from the permanent magnet motor such that the permanent
magnet motor
directly rotates the shaft. The direct drive drawworks further includes a drum
connected to the
shaft away from the permanent magnet motor such that the rotation of the shaft
causes a
corresponding rotation of the drum.
[0029] The housing may have an interior chamber surrounded by a wall, the
stator being
positioned adjacent the wall, the rotor being positioned interior of the
stator.
[0030] The stator may have a plurality of windings extending in spaced
relation around an
interior surface of the stator, the rotor being an annular member having a
plurality of permanent
magnets mounted in spaced relation around a periphery of the rotor.
[0031] The plurality of windings may extend radially inwardly toward the
rotor, the plurality of
windings acting on the plurality of permanent magnets so as to cause a
rotation of the rotor.
[0032] The drive plate may have an aperture centrally formed therein, the
drive plate having
splines extending inwardly into the aperture, the shaft having a splined end
engaged with the
splines of the drive plate.
[0033] The direct drive drawworks may include a bearing housing connected to
the permanent
magnet motor, the shaft extending through and rotatably supported by the
bearing housing.
[0033a] The bearing housing may be interposed between the permanent magnet
motor and the
drum.
[0033b] The direct drive drawworks may include braking provisions receiving
the shaft therein,
the braking provisions for exerting a force on the shaft so as to resist the
rotational movement
thereof.
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[0033c] The braking provisions may be positioned adjacent an end of the drum
opposite the
permanent magnet motor.
[0033d] The direct drive drawworks may include a power supply electrically
connected to the
permanent magnet motor so as to supply electrical energy thereto.
[0033d] The direct drive drawworks may include a wire line extending around
the drum, the
drum being rotatable so as to pay in and pay out the wire line.
[0033e] The direct drive drawworks may include a derrick, a pulley positioned
on the derrick,
the wire line extending over the pulley, and a traveling block connected to
the wire line and
extending downwardly from the pulley.
[0033f] In accordance with another disclosed aspect there is provided a
drilling rig. The drilling
rig includes a derrick, a pulley supported by the derrick, a wire line
extending over the pulley so
as to have an end extending downwardly therefrom, a traveling block
interconnected to the end
of the wire line, a drum positioned adjacent a bottom of the derrick, the wire
line extending
around the drum, and a shaft connected to the drum and extending outwardly
therefrom. The
drilling rig also includes a permanent magnet motor receiving a shaft therein,
the permanent
magnet motor for imparting a rotational force to the shaft so as to rotate the
drum in order to pay
in or pay out the wire line. The permanent magnet motor includes a housing, a
stator positioned
in the housing, and a rotor cooperative with the stator, the rotor having a
drive plate affixed
thereto, the shaft being directly connected to the drive plate.
[0033g] The stator may have a plurality of windings extending in spaced
relation around an
interior surface of the stator, the rotor being an annular member and having a
plurality of
permanent magnets mounted in spaced relation around a periphery of the rotor.
[0033h] The drilling rig may include a bearing housing connected to the
permanent magnet
motor, the shaft extending through and rotatably supported by the bearing
housing.
[0033i] The drilling rig may include braking provisions receiving the shaft
therein, the braking
provisions for exerting a force on the shaft so as to resist the rotational
movement thereof.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0034] FIGURE 1 shows a side elevational view of an oil rig utilizing a prior
art drawworks.
[0035] FIGURE 2 shows a side elevational view of the preferred embodiment of
the permanent
magnet direct drive drawworks of the present invention.
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[0036] FIGURE 3 shows a perspective view of the preferred embodiment of the
permanent
magnet direct drive of the present invention.
[0037] FIGURE 4 shows a cross-sectional view of the permanent magnet motor of
the present
invention.
[0038] FIGURE 5 shows a plan view of the drive plate associated with the
permanent magnet
motor of the present invention.
[0039] FIGURE 6 shows a perspective view of the rotor of the permanent magnet
motor of the
present invention.
[0040]FIGURE 7 shows a perspective view of the stator of the permanent magnet
motor of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
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[0041] Referring to FIGURE 2, there is shown a side elevational view of the
preferred embodiment
of the permanent magnet direct drive drawworks 100 of the present invention.
The drawworks 100
has a permanent magnet motor 40. A shaft 41 is connected to the permanent
magnet motor 40. A
bearing housing 45 is positioned adjacent the permanent magnet motor 40 and
the shaft 41. The shaft
41 extends through the bearing housing 45 and into the interior of the motor
40. A drum 43 is
attached to the end 47 of the shaft 41 opposite the permanent magnet motor 40.
The wire line 24
wraps around the drum 43. The drum 43 is in cradle 53. The cradle 53 supports
the shaft 41 so as
to hold the drum 43 and motor 40 above the floor surface, e.g. the rig floor
12. A braking system
49 is positioned on a side of the drum 43 opposite the motor 40. In FIGURE 2,
the braking system
49 has a brake disk 51 positioned adjacent the drum 43. The braking system 49
in FIGURE 2 is
water-cooled. A power supply 48 is connected to the permanent magnet motor 40
so as to supply
power thereto.
[0042] The permanent magnet motor 40 rotates the shaft 41 which rotates the
drum 43. The rotation
of the drum 43 causes the wire line 24 to be extended or retracted depending
upon the direction of
rotation of the drum 43. When the wire line 24 is retracted, the wire line 24
wraps around the outer
surface of the drum 43. A longitudinal axis of the drum 43 is aligned with a
longitudinal axis of the
shaft 41. The longitudinal axes of the drum 43 and shaft 41 are generally
parallel to the rig floor 12.
[0043] Referring to FIGURE 3, there is shown a perspective view of the
permanent magnet direct
drive drawworks 100 of the present invention. The permanent magnet motor 40
has a housing 42.
A rotor and stator are located within the housing 42, as is described in more
detailed hereinafter. The
housing 42 has a generally cylindrical shape. The housing 42 has an inlet 55
and an outlet 57. In
order to cool the rotor and stator of the motor 40, air is passed into the
inlet 55, circulated in the
interior of the housing 42, and discharged through the outlet 57. A cover 50
is affixed to the top
surface 44 of the housing 42. The disk 51 of the braking system 49 is
positioned adjacent the drum
43 inside the cradle 53. The drum 43 is shaped like a yarn spool so as to
efficiently store long
lengths of wire.
[0044] The drum 43 has a wire line wrapped therearound. The rotation of the
drum 43 serves to pay
in and pay out this wire line. The wire line extends from the drum 43 in the
manner described herein
previously in connection with FIGURE 1. As such, the rotation of the drum 43,
as caused by the
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permanent magnet motor 40, can cause the wire line to pay in and pay out for
the purpose of lifting
or lowering the traveling block.
[0045] Referring to FIGURE 4, there is shown a cross-sectional view of the
housing 42 of the
permanent magnet motor 40. As can be seen, the housing 42 defines an interior
chamber 60. The
shaft 41 extends outwardly of the interior 60 of the housing 42 of the
permanent magnet motor 40.
A stator 62 is affixed to the wall of the housing 42. The stator 62 extends
around the circular interior
of the housing 42. A rotor 64 is positioned in close proximity to the stator
62. Rotor 64 has a
plurality of permanent magnets formed around a periphery thereof (described in
more detail
hereinafter). The stator 62 has coils of wire positioned around the inner
surface of the stator 62. The
interaction of the coils of the stator 62 and the permanent magnets of the
rotor 64 provides the
rotational power of the permanent magnet motor 40. A drive plate 66 is affixed
to the top of the
rotor 64. The shaft 41 is engaged with the drive plate 66 so that the
rotational energy imparted to
drive plate 66 by the rotor 64 will be imparted to the shaft 41. The shaft 41
extends outwardly from
the interior chamber 60 of the housing 42. An end of the cradle 53 can be seen
as positioned
between the bearing housing 45 and the motor 40. Thus, the shaft 41 extends
through the motor 40,
the cradle 53, and the bearing housing 45.
[0046] Permanent magnet motors rotate because of the torque that the
interaction of two magnet
fields causes. These magnetic fields are created by the permanent magnets
mounted on the rotating
rotor and the magnetic field that the stationary windings of the stator
induce. The torque is greatest
when the magnetic vector of the rotor is at 90 to the magnetic vector of the
stator. In this position,
it forces the poles of the rotor to rotate in the direction of the stator
field. In a trapezoidally-driven
brushless-DC motor, a current flow alternating sequentially through two of the
three coils generates
the stator field. The remaining third coil monitors the back EMF
(electromotive force) of the two
active coils. Back EMF occurs when a permanent magnet motor rotates. Each
winding generates
a voltage that opposes the main voltage of the windings. Back EMF depends on
the angular velocity
of the rotor, the magnetic field that the rotor magnets generate, and the
number of turns in the stator
windings. The motor's back EMF provides the feedback of the rotor's position
with respect to the
stator windings. Permanent magnet motors having sensors provide a similar
position feedback. With
sinusoidal commutation, which permanent magnet synchronous motor use, the
drive-control circuitry
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simultaneously powers the three coils.
[0047] Permanent magnet motors have been commercially available since the
1990's. However,
permanent magnet motors have not seen widespread use because of the high cost
associated with the
expensive permanent magnets on the rotor. Additionally, their complex control
algorithms requires
specialized engineering expertise as well as the additional expense of an
embedded processor.
Permanent magnet motors are more efficient than the AC-induction motors.
However, because of
the recent rise in the price of copper, the current winding-based induction
motors have become more
costly and the permanent magnet motors have become comparatively less
expensive. Additionally,
recent advances in technology have improved the power output of permanent
magnet motors to
where such motors have a superior power density to that of existing induction
motors. As such, the
permanent magnet motor 40, as illustrated in FIGURE 4, provides superior power
output for the
direct drive of the shaft 41 and drum 43 of the drawworks 100.
[0048] Referring to FIGURE 5, there is shown a plan view of the drive plate 66
of the permanent
magnet motor 40 of the drawworks 100 of the present invention. The drive plate
66 has a circular
shape with the an outer periphery 90. Bolt holes 92 are formed adjacent to the
outer periphery 90.
The bolt holes 92 allow for the bolted attachment of the drive plate 66 of the
top of the rotor. A
splined aperture 94 is formed centrally of the drive plate 66 so as to
accommodate the spline of the
shaft 41. Air circulation holes 96 are formed around the interior of the drive
plate 66. The holes
96 facilitate air circulation within the permanent magnet motor 40.
[0049] Referring to FIGURE 6, there is shown a isolated perspective view of
the rotor 64 of the
permanent magnet motor 40 of the drawworks 100 of the present invention. The
drive plate 66 can
be mounted directly onto the top of the rotor 64. Permanent magnet piles are
affixed to the outer
surface of the rotor 64 in spaced relationship to each other. Spacers 106
serve to isolate one of the
permanent magnet piles from an adjacent pile. Spacers 106 can be separate
items or they can be
simply a formed surface on the outer periphery on the rotor 64. The rotor 64
has a rotor bearing
bore 110 formed centrally thereof.
[0050] Referring to FIGURE 7, there is shown a isolated perspective view of
the stator 62 of the
permanent magnet motor 40 of the drawworks 100 of the present invention. The
stator 62 has an
outer cover 120 which serves to space the coils 122 from the inner wall of the
housing 42. The coils
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122 extend radially inwardly therefrom. The interior surface 124 of the coils
122 define a circular
aperture into which the rotor 64 is placed. As a result, the permanent magnet
piles 104 are in close
proximity to the coils 122 so that the permanent magnet motor 40 can operate
properly. Suitable
electronics are connected to the permanent magnet motor 40 so as to facilitate
the proper operation
of the permanent magnet motor 40.
100511 In the present invention, it will be appreciated that the permanent
magnet direct drive
drawworks 100 is directly connected to the shaft 41. As such, there are no
gears or other
transmission mechanisms that are interconnected in these areas. The drawworks
100 thus provides
an enhanced power density for the proper rotation of the drillstring in a
relatively lightweight
configuration. The weight associated with transmission systems is effectively
avoided by the present
invention. Furthermore, the complexity of installing such transmission systems
so that the power
of the induction motor can be transmitted to the drive system is avoided in
the present invention.
As a result, the permanent magnet direct drive drawworks of the present
invention can serve the
proper purpose of rotating the drillstring with a minimal weight. Unlike the
present motors
associated with drilling operations that can weigh in excess of 100,000
pounds, the permanent
magnet motor of the present invention will only weigh approximately 60,000
pounds. As such, it
can be easily transported over roads on a conventional truck. Unlike the prior
art, the motor 40 does
not have to be assembled in itself or with the transmission system in the
field. As such, the present
invention avoids the specialized requirement of installation personnel that
would be otherwise
required for those systems that require transmissions between the motor and
the drawworks. The
reduced weight of the permanent magnet motor of the present invention avoids
certain inertial effects
that would otherwise adversely affect the operation of conventional induction
motors. The motor
40 of the present invention can be interchanged, as desired, for use in
association with the direct
drive top drive of the drilling rig or the mud pump of the drilling rig. Since
transmission systems
are not required, a supply of such permanent magnet motors can be provided to
the drilling operation
for use either in association with a drawworks or for other purposes. If there
would be a failure of
any one motor, then any of the other motors could be substituted therefore
without any downtime
on the drilling rig.
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[0052] While specific embodiments have been described and illustrated, such
embodiments
should be considered illustrative only and not as limiting the invention as
defined by the
accompanying claims.
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