US006388353B1

(12) United States Patent

(16) Patent N6;

Liu et al.

(54)

(45) Date of Patent:

ELONGATED PERMANENT MAGNET

3,780,324 A

SYNCHRONOUS MOTOR

3,838,322 A

Inventors:

Joseph
C. Liu,
- Tulsa,
~
OK (US);
~

gllcllgasrgsgvgitglsig?ezgig

9/1974 Greenwell

(73)

AsslgneeZ Came" Internatlonal, In->H1Stn>

TX (Us)

( * )

Notice:

4,918,831

318/225 R

Greenwell

....... .. 318/227

51mg
c aine a.~ ~ ~

.....
~ ~ ~ ~~ ..

1/1988 (31161616161. ............ .. 417/14

*

4/1990

Kliman

5/1991

Sneddon

. ... ... .

.. ... .

. . . . ..

29/598

. . . . ..

415/72

5,179,306 A * 1/1993 Nasar ................. .. 310/14

5,355,044 A * 10/1994 Uchida 618.1. ..
310/162
A

1/1995

Andersen

Subject to any disclaimer, the term of this

5,407,337 A

4/1995

Appleby _ _ _ _ _ _

patent is extended or adjusted under 35

U.S.C. 154(1)) by 0 days.

5,708,337 A
5,951,262 A

1/1998 Breit et al. ..

318/439
9/1999 Hartman ................... .. 417/356

(21) Appl. NO.Z 09/539,083

. ... ... .

. . . ..

210/743

_ _ _ __ 418/166

med by exammer

M31; 30, 2000

Primary ExaminerBurton S. Mullins

7
(51)

5,017,087

5,378,374

(22) Filed;

12/1974

4,718,824 A

May 14, 2002

12/1973 Greenwell ................ .. 310/180

3,854,077 A
(75)

US 6,388,353 B1

(74) Attorney, Agent, or FirmFletcher, Yoder & Van

Int. Cl. ...................... .. H02K 21/14; H02K 15/03;

Someren

F04B 17/00
(52)

US. Cl. .......................... .. 310/156.09; 310/156.09;

310/15647; 310/87; 310/114; 417/4237

(58)

Field of Search ............................ .. 310/87, 156.47,

310/15608, 156.09, 156.11, 112, 114; 417/4101,

423.7, 424.1, 424.2
,

(56)

References Clted
[)3 PATENT DOCUMENTS

(57)

ABSTRACT

A permanent magnet synchronous motor system. The sys

tem uses a permanent magnet AC synchronous motor having

an elongated housing, of the type used in progressive cavity

pumping applications. Within the stator, a multi-section
rotor is rotatabl mounted. The rotor includes a luralit of

rotor sections tll/at are angularly offset from eachpother. 2The

rotor sections are mounted on a drive shaft, and the sum of

the offsets is generally comparable to the angular displace

2,976,807 A

3/1961 Hill ........................... .. 103/11

ment undergone by the drive Shaft under a normal Operating

3,568,771 A

3/1971 Vincent et al. ........... .. 166/250

load

3,751,192 A
3,753,060 A

8/1973
8/1973

3,753,062 A

8/1973 Greenwell ............ .. 318/225 R

Boyd ....................... .. 417/411

Greenwell
..... .. 318/227

'

22 Claims, 5 Drawing Sheets

U.S. Patent

May 14, 2002

FIG. 1

Sheet 1 0f 5

US 6,388,353 B1

22

w 24

3 PHAQ

460 v

FLUX

STEP-UP

-'

"Egg" ' TRANSFORMER "

28

30

JBOX

26

U.S. Patent

May 14, 2002

US 6,388,353 B1

Sheet 2 0f 5

FIG. 2

42'
._/ 38

18...,

Joel

J54
74

4-58

U.S. Patent

May 14, 2002

FIG. 5

Sheet 3 0f 5

US 6,388,353 B1

U.S. Patent

May 14, 2002

Sheet 5 0f 5

US 6,388,353 B1

FIG. 6

O
)

US 6,388,353 B1
1

ELONGATED PERMANENT MAGNET

SYNCHRONOUS MOTOR

magnet synchronous motor are designed for deployment in

a Wellbore to pump a Wellbore ?uid. The system also

includes a variable speed drive able to output a three-phase

alternating current. A poWer cable connects the variable

FIELD OF THE INVENTION

speed drive to the permanent magnet synchronous motor to

directly supply alternating current from a remote location to

The present invention relates generally to electric motors,

and particularly to elongated permanent magnet synchro

the submersed motor.

nous motors utilized in, for example, doWnhole, progressive

According to another aspect of the present invention, a

method is provided for counteracting the effects due to shaft

cavity pumping systems.

BACKGROUND OF THE INVENTION

tWist in an electric motor under load. The method includes

mounting a ?rst rotor section and a second rotor section

In a variety of applications, it is advantageous to utiliZe an

elongated motor having a relatively long stator and rotor
mounted therein. For example, elongated induction motors

Within a stator. Additionally, the method includes attaching

a ?rst plurality of permanent magnets along the ?rst rotor
section and a second plurality of permanent magnets along
the second rotor section. The ?rst plurality of magnets is

are utiliZed in progressive cavity pumping applications,

15

because they can be designed to ?t Within the con?nes of a

Wellbore. Induction motors are also bene?cial in that they
are not detrimentally affected by shaft tWist due to loading

angularly offset With respect to the second plurality of

magnets.
According to another aspect of the present invention, a

of the elongated motor. HoWever, the rotational speed of

induction motors is relatively high and varies With load. In
some applications, such as doWnhole progressive cavity
(PC) pump systems, it Would be advantageous to utiliZe a

progressive cavity pumping system is provided. The system

includes a progressive cavity pump and a permanent magnet

synchronous motor coupled to the progressive cavity pump.

The output of the motor is directly coupled to the pump such
that the pump rotates at the motor speed. In other Words, the

motor that operates at a loWer rotational speed than an

induction motor.

In PC Pump applications, for instance, conventional

rotational speed of the permanent magnet synchronous

25

motors must be combined With a gearbox to reduce the

motor and the progressive cavity pump are generally at a 1:1

ratio.

rotational speed of the output shaft. A gearbox adds expense

and complexity to the overall system.
Permanent magnet synchronous motors can be designed

The invention Will hereafter be described With reference

BRIEF DESCRIPTION OF THE DRAWINGS

to the accompanying draWings, Wherein like reference

numerals denote like elements, and:

to operate at a loWer speed that remains constant over certain

ranges of variable load. HoWever, an elongated permanent

magnet synchronous motor is very susceptible to shaft tWist.
When a suf?cient load is placed on the driving shaft, the
resultant tWisting tends to move the permanent magnets that

FIG. 1 is a schematic representation of a submersible

pumping system utiliZing a permanent magnet synchronous

motor supplied With alternating current from a remote

are mounted on the rotors out of the optimal or desired 35 location, according to a preferred embodiment of the present

rotational position relative to the stator. Permanent magnet

invention;

synchronous motors are also dif?cult to start from a remote

FIG. 2 is a front elevational vieW of a submersible

location. For example, if a permanent magnet synchronous

pumping system utiliZing an elongated motor, according to

motor is used in a doWnhole, Wellbore environment, it is

a preferred embodiment of the present invention;

dif?cult to start the motor With a conventional controller

disposed at the surface of the earth.

It Would be advantageous to have a permanent magnet
synchronous motor designed to self start in a doWnhole
location and to compensate for the amount of shaft tWist that
occurs under normal loading.

FIG. 3 is a cross-sectional vieW of the electric motor,

taken generally along line 33 of FIG. 2;

FIG. 4 is a side vieW of a rotor assembly utiliZed With the

SUMMARY OF THE INVENTION

motor illustrated in FIG. 2;

FIG. 5 is a side vieW of a shaft having a plurality of offset
keyWays to accommodate offset rotor sections;
FIG. 6 is a side vieW of an alternate shaft having a single

The present invention features a permanent magnet syn

chronous motor system. The system comprises a permanent

FIG. 7 illustrates rotor sections having offset keyWays to

provide offset rotor sections.

45

keyWay; and

magnet synchronous motor including an elongated housing.

DETAILED DESCRIPTION OF THE

PREFERRED EMBODIMENTS

A stator is disposed Within the housing and includes a

plurality of Windings. Additionally, a rotor is rotatably

disposed Within the stator and includes a plurality of rotor
sections. Each rotor section includes several permanent

magnets that lie generally parallel With the axis of the rotor
section. When the rotor sections are mounted on the shaft,

the permanent magnets of adjacent or sequential rotor sec

tions are offset from each other a predetermined angular

displacement. The sum of the predetermined angular dis

placements is approximately equal to the angular displace

ment of the shaft under a given load.

55

Referring generally to FIG. 1, a schematic representation

of a permanent magnet synchronous motor system 10 is
illustrated according to a preferred embodiment of the

present invention. System 10 includes a progressive cavity

pumping system 12 disposed Within a Wellbore 14. Progres
sive cavity pumping system 12 includes an electric motor 16
that receives poWer via a poWer cable 18. Typically, poWer
cable 18 includes at least three conductors 20 for carrying

According to another aspect of the present invention, a

three-phase poWer, such as 460 volt, three-phase poWer. By

Way of example, electric motor 16 is a three-phase, eight

progressive cavity submersible pumping system is designed

pole permanent magnet AC synchronous motor designed to

for use Within a Wellbore. The system includes a progressive 65 operate on three-phase poWer.

cavity pump driven by a permanent magnet synchronous

motor. Both the progressive cavity pump and the permanent

In the embodiment illustrated, an alternating current is

supplied to electric motor 16 via poWer cable 18 from a

US 6,388,353 B1
3

control system 22 disposed at a remote location 24. An

exemplary remote location 24 is at or above a surface 26 of
the earth. An exemplary control system 22 includes a
variable speed drive 28, such as a ?ux vector-type variable

Motor 16 preferably comprises an elongated housing 50

that is generally tubular in shape. Disposed Within elongated

speed drive. An exemplary drive is the Reda Speed Star

2000, available from Reda Production Systems of
Bartlesville, Okla. Additionally, control system 22 may

housing 50 is a core or stator 52 that includes a plurality of

Windings 54. The combined stator 52 and Windings 54

5

having conductive coils extending longitudinally there

through.

include a transformer 30 coupled to variable speed drive 28.

Transformer 30 is designed to step up the voltage, as

necessary, for certain applications. Furthermore, transformer

30 is designed to eliminate the possibility of magnetic

typically are formed from a plurality of plates or laminations

As illustrated further in FIG. 3, stator 52 includes a

10

central, longitudinal opening 56 siZed to rotatably receive a

rotor assembly 58. Rotor assembly 58 includes a plurality of

saturation at loW frequency. A junction box 32 is utiliZed to

rotor sections 60 (see also FIG. 4). Rotor sections 60 are

connect transformer 30 With poWer cable 18.

mounted over a drive or driving shaft 62. Each rotor section

The unique arrangement of control system 22 and motor

60 is prevented from moving rotationally With respect to

16 of progressive cavity pumping system 12 permits

consistent, dependable running and self-starting of progres

shaft 62 by a relative rotation prevention system 64. An

exemplary rotation prevention system 64 is a key and
keyWay system in Which each rotor section 60 includes a
keyWay 66 that extends radially outWard from an inner, axial
rotor opening 68 siZed to receive drive shaft 62.

15

sive cavity pumping system 12. Preferably, motor 16 is an

eight-pole motor designed to operate at a relatively sloW
speed in the range from approximately 12 to 40 HZ. The
alternating current can be supplied directly from control
system 22 at a remote location 24. Thus, if progressive

Additionally, drive shaft 62 includes one or more coop

20

cavity pumping system 12 is deep Within a Wellbore, eg

erating keyWays 70 that extend into drive shaft 62 in a

radially inWard direction. The one or more keyWays 70 are

3000 feet or more, motor 16 is able to consistently self-start

disposed for cooperation With each rotor section 60. A key

72 is siZed for receipt in keyWays 66 and 70 at each rotor

and operate. Preferably, motor 16 also utiliZes high energy

permanent magnets, such as samarium cobalt (SmCo5)

section 60 to prevent rotational movement of that rotor

magnets. The use of a motor having a greater number of 25
section relative to drive shaft 62. If a single keyWay 70 is

poles, eg an eight-pole or tWelve-pole motor With such high

energy permanent magnets permits the motor to be started

disposed along shaft 62, a single key can be used along the
drive shaft 62 or individual keys at each rotor section 60.
If rotor assembly 58 is utiliZed in a permanent magnet

from a location remote from the motor.

A typical application of electric motor 16 is described

With reference to FIGS. 2 through 4. As illustrated best in

30

FIG. 2, motor 16 is disposed in an exemplary progressive

synchronous motor, each rotor section 60 includes a plural

ity of permanent magnets 74. Permanent magnets 74 are

cavity pumping system 12. Elongated motor 16 is particu

elongated magnets that lie generally parallel With drive shaft

larly amenable for use in environments that require a rela

62 and the axis about Which it rotates. Each rotor section 60

is designed With a plurality of seats 76 that run longitudi

tively long but narroW physical con?guration of the motor,

e.g. Within a Wellbore. In this application, system 12 is
designed for deployment in a Well 34 Within a geological
formation 36 containing desirable production ?uids, such as
petroleum. The Wellbore 14 is drilled into geological for
mation 36 and aligned With a Wellbore casing 38. System 12
is deployed Within Wellbore 14 to a desired location for
pumping of the Wellbore ?uids.

35

is siZed to receive a corresponding permanent magnet 74. In

the preferred embodiment, the plurality of seats 76 may

include, for example, eight seats 76 for receiving eight

permanent magnets 74. Each seat area 76 is divided from
40

The illustrated progressive cavity pumping system 12 also

includes other components. For example, motor 16 poWers
a progressive cavity pump 40, and is protected by a motor
protector 42. Motor protector 42 is designed to protect motor
16 from contamination by Wellbore ?uids, and to permit
equaliZation of the internal pressure of motor 16 With the
external pressure in Wellbore 14. A thrust chamber 43 is
disposed betWeen protector 42 and pump 40. HoWever,
because system 10 permits the use of a permanent magnet

nally along the corresponding rotor section 60. Each seat 76

adjacent seat areas 76 by longitudinal ribs 78. Permanent

magnets 74 may be af?xed to their respective seats 76 by, for
example, an adhesive bonding. Drive shaft 62 and the
plurality of rotor sections 60 preferably are supported by

appropriate bearing sets 80 (see FIGS. 2 and 4) disposed

45

betWeen adjacent rotor sections 60.

During operation, the Windings 54 of stator 52 are ener
giZed in a temporal sequence. This provides a magnetic ?eld
that moves either clockWise or counterclockWise around the
core or stator 52. The moving ?eld intersects With the ?ux

50

?eld of the permanent magnets 74 and causes rotor assembly

synchronous motor 16, the rotational speed is relatively

58 to rotate in the desired direction.

sloW, eg in the 12 to 40 HZ range, pumping system 12 does

As discussed above, a problem With elongated motors,

such as permanent magnet synchronous motor 16, is that
drive shaft 62 tWists under operating load. In other Words,
once motor 16 is operating, the opposing ends of drive shaft

not require a speed reducing gearbox. In other Words, the

output of motor 16 can be used to directly poWer pump 40
Without the expense of adding a gearbox, as in prior art

55

62 are angularly displaced from one another relative to their

position When motor 16 is not operating. This leads to poor

progressive cavity pump systems. This can substantially

reduce the cost of pumping system 12 and also removes one
more component that Would otherWise be susceptible to

cooperation betWeen the magnetic ?eld moving through

Wear or breakage.

Progressive cavity pumping system 12 typically is sus

60

60 are at non-optimal positions relative to stator 52, resulting

in reduced output poWer and inef?cient operation of motor
16.

pended in Wellbore 14 by a deployment system 44, such as

coil tubing, cable or the illustrated production tubing 46.

Deployment system 44 is connected to progressive cavity

pumping system 12 by an appropriate head or connector 48.

Furthermore, poWer is supplied to elongated motor 16 by

poWer cable 18, Which is routed along deployment system
44 from the earths surface.

stator 52 and the location of permanent magnets 74. The

permanent magnets 74 of at least some of the rotor sections

65

As illustrated in FIG. 4, at least some of the rotor sections

60 are angularly offset from each other to compensate for the

tWisting of drive shaft 62. Speci?cally, the permanent mag

nets 74 of sequential rotor sections 60 are offset from one

US 6,388,353 B1
5

another by a given offset 82. The actual angular distance of

each offset 82 depends on the torque carried by the shaft, the

example, a variety of control systems can be used to provide

alternating current to the submersible pumping system; a
Wide range of motor lengths and diameters can bene?t from
the present invention; the design and number of rotor
sections utiliZed may vary from one application to another;
motors other than permanent magnet synchronous motors
may bene?t from the utiliZation of offset rotors; and the
unique electric motor may be utiliZed in applications other
than submersible pumping systems. These and other modi
?cations may be made in the design and arrangement of the
elements Without departing from the scope of the invention
as expressed in the appended claims.
What is claimed is:
1. Apermanent magnet synchronous motor system, com

number of rotor sections 60, and the number of rotor

sections that are actually offset from each other. For
example, if rotor assembly 58 includes ten rotor sections 60,

and the load application on motor 16 angularly displaces,

i.e., tWists, shaft 62 by, for example, 30 degrees, then the

sum of offsets 82 preferably is approximately 30 degrees. If
the exemplary motor 16 utiliZes ten rotor sections 60, then
each rotor section can be displaced approximately three
degrees from the position of the next adj acent rotor for an
offset sum that equals approximately 30 degrees. If some of

10

the rotors are not offset or if the number of rotors is greater

or less than ten, the angular distance of each offset 82 is

adjusted accordingly to reach a desired offset sum, eg 30

15

prising:
a permanent magnet synchronous motor having an elon

degrees.

gated housing; a stator having a plurality of Windings;

The angular direction or progression of offsets 82 is

designed to compensate for shaft tWist. For example, if rotor
assembly is rotated in the direction of arroW 84 in FIG. 4,

and a rotor rotatably disposed Within the stator, the

rotor including a plurality of rotor sections, each rotor

(at the indicated Top End) tends to tWist shaft 62 in the

section including a plurality of permanent magnets, the

permanent magnets of adjacent rotor sections being

direction of arroW 86. This tWisting of shaft 62 tends to

remove the offsets 82 betWeen rotor sections 60. In other

displacement, the plurality of rotor sections being

then a load applied to shaft 62 in the direction of arroW 86

offset from each other a predetermined angular

mounted over a shaft With each rotor section rotatably

Words, the predetermined shaft tWist tends to align magnets

74 of sequential rotor sections 60 for optimiZation of motor

25

performance under load.

The permanent magnets 74 of sequential rotor sections 60

keyWays, each keyWay being at an axially unique

location and being offset from each adjacent keyWay by

can be offset in a variety of Ways. HoWever, one method is

the predetermined angular displacement.

to offset the keyWays 70 along shaft 62 to control the offset

of each rotor section. Referring to FIG. 5, a portion of shaft
62 is illustrated to include a plurality of keyWays 66 that are
angularly displaced from each other a distance equal to

2. The permanent magnet synchronous motor system as

recited in claim 1, further comprising a progressive cavity

pump poWered by the permanent magnet synchronous

motor.

offsets 82. Thus, When rotor sections 60 are assembled over

shaft 62 the corresponding key 72 and rotor section keyWay

66 cooperate to hold speci?c rotor sections at the desired

35

3. The permanent magnet synchronous motor system as

recited in claim 2, further comprising a motor protector

coupled to the permanent magnet synchronous motor.

4. The permanent magnet synchronous motor system as
recited in claim 3, further comprising a variable speed drive
electrically connected to the permanent magnet synchronous

angular position. Thus, rotor assembly 58 can be readily

designed for a given load and resultant angular displacement
of shaft 62.
An alternate embodiment of rotor assembly 58 is illus
trated in FIGS. 6 and 7. In this embodiment, shaft 62

motor.

5. The permanent magnet synchronous motor system as

recited in claim 4, Wherein the variable speed drive is at a

includes a linear keyWay 90 that preferably extends along

the length of the shaft. The linear keyWay tends to be less

location remote from the permanent magnet synchronous

motor and the permanent magnet synchronous motor is

expensive to manufacture relative to a plurality of offset

keyWays.

?xed With respect to the shaft by a corresponding key

and keyWay, Wherein the shaft includes a plurality of

45

self-starting.
6. The permanent magnet synchronous motor system as

In this embodiment, the offsets 82 are created by forming

a linear keyWay 92 in each rotor section 60 at a unique

recited in claim 5, Wherein the permanent magnet synchro

angular position. Instead of angularly offsetting the magnets

nous motor is positioned in a Wellbore and the variable speed

74 of sequential rotor sections by offset keyWays on the

shaft, the keyWay 92 formed in each rotor section 60 is
disposed at a unique location relative to position 74. An
exemplary group of offset rotor keyWays 92 is indicated in
FIG. 7 by the keyWay 92 and the dashed-line keyWays

drive is positioned outside of the Wellbore.

7. The permanent magnet synchronous motor system as
recited in claim 1, Wherein the permanent magnets of
adjacent rotor sections are offset by offsetting each corre

sponding key and keyWay relative to the next adjacent key

and keyWay.

92A92D. The phantom keyWays represented by reference

numerals 92A92D shoW the angular position of keyWays

55

relative to magnets 74 in sequential rotor sections. Of

course, When each of the rotor sections is disposed over shaft

keyWay disposed at a unique angular position relative to the

rotor sections permanent magnets.
9. Apermanent magnet motor doWnhole pumping system

62 and held in rotational position by a key 94, keyWays 92,

92A, 92B, 92C, and 92D are aligned and magnets 74 of
sequential rotor sections 60 are offset by the predetermined
offset 82. Once the shaft is under normal operating load and
consequential shaft tWist, the magnets 74 of sequential rotor
section 60 are generally aligned to optimiZe motor perfor

designed for use Within a Wellbore, comprising:

a doWnhole pump; and

mance.

It Will be understood that the foregoing description is of

preferred exemplary embodiments of this invention, and that
the invention is not limited to the speci?c forms shoWn. For

8. The permanent magnet synchronous motor system as

recited in claim 7, Wherein each rotor section includes a

65

a permanent magnet motor coupled to the doWnhole

pump, Wherein the doWnhole pump and the permanent
magnet motor are designed for deployment in a Well
bore to pump a Wellbore ?uid, and Wherein the perma
nent magnet motor includes a plurality of rotor
sections, each rotor section having a plurality of per

US 6,388,353 B1
8

7
manent magnets, the permanent magnets of adjacent
rotor sections being offset from each other by a prede
termined angular displacement, Wherein the sum of the

a permanent magnet synchronous motor coupled to the

predetermined angular displacements betWeen each

sections, each rotor section having a plurality of per

rotor section is approximately equal to the angular

manent magnets, the permanent magnets of adjacent

rotor sections being offset from each other by a prede
termined angular displacement, Wherein the sum of the

progressive cavity pump, Wherein the permanent mag

net synchronous motor includes a plurality of rotor

tWisting of the shaft under a standard load.

10. The permanent magnet motor doWnhole pumping

system as recited in claim 9, further comprising:
a poWer supply able to output a three-phase alternating
current;
a variable speed drive; and
a poWer cable connecting the variable speed drive to the
permanent magnet motor.
11. The permanent magnet motor doWnhole pumping
system as recited in claim 10, Wherein the permanent magnet
motor is an eight pole, self-starting motor.
12. The permanent magnet motor doWnhole pumping
system as recited in claim 11, Wherein the permanent magnet

predetermined angular displacements betWeen each

rotor section is approximately equal to the angular
10

tWisting of the shaft under a standard load.

17. The progressive cavity pumping system, as recited in

claim 16, Wherein the rotational speed of the permanent
magnet synchronous motor and the progressive cavity pump
are generally at a 1:1 ratio.
15

18. The progressive cavity pumping system, as recited in

claim 17, further comprising a motor protector coupled to

the permanent magnet synchronous motor.

19. The progressive cavity pumping system, as recited in
claim 18, further comprising a thrust chamber coupled to the

motor includes a drive shaft on Which the plurality of rotor

progressive cavity pump.

sections are mounted.

20. The progressive cavity pumping system, as recited in

claim 17, further comprising a variable speed drive electri

13. The permanent magnet motor doWnhole pumping

system as recited in claim 9, Wherein the drive shaft includes
a plurality of keyWays that are angularly offset from each
other.

14. The permanent magnet motor doWnhole pumping

cally connected to the permanent magnet synchronous

motor.
25

21. The progressive cavity pumping system, as recited in

claim 17, Wherein the permanent magnet synchronous motor

system as recited in claim 9, Wherein each rotor section

includes a drive shaft on Which the plurality of rotor sections

includes a keyWay disposed at a unique angular position

are mounted.

relative to the rotor sections permanent magnets.

15. The permanent magnet motor doWnhole pumping

system as recited in claim 9, Wherein the poWer supply
comprises a variable speed drive.

16. A progressive cavity pumping system, comprising:

a progressive cavity pump; and

22. The progressive cavity pumping system, as recited in

claim 16, Wherein each rotor section includes a keyWay
disposed at a unique angular position relative to the rotor

sections permanent magnets.