VARIABLE SPEED DRIVE "REGENERATIVE" TYPE- LESSONS LEARNT -

GuyDESCORPS Philippe ESPAGNE Claudiu NEACSU Philippe WESOLOWSKITOTAL TOTAL LEROY SOMER LEROY SOMERAvenue Larribau Avenue Larribau Usine de CEB Engineering Dpt.Pau Pau Beaucourt AngoulemeFrance France France France

Abstract - Variable speed A.C. drives are used in many new During phase 1, the operating experience allowed us to noticeand already existing oil and gas applications because of their that the bound constraints engendered important problems.well known benefits for energy efficiency and flexible control of Works over operations were necessary to replace pumpsprocess. because the sizing was not adapted to the productivity of wells.

Considering the acquired experience, for the phases 2 and 3During the past years, numerous publications [R6f] have been development, the VSD option was considered.published relating to the various technologies of electronicVariable Speed Drives (VSD) for Electric Submersible Pumps 1 ESP l5lhp(ESP) application. This paper explains why a "Regenerative" 8 ESP 222hp Phase 3VSD new technology had been chosen in a specific project to DPi WP2 5 ESP 540hpsupply ESP (PART I). Moreover we will present also the main 6 ESP 270hpbenefits of using this technology when both motor and VSD Rhhave to comply with ATEX category 2 or 3 (PART 2). 1haeS 260hp

42km 25 EP 270hpThis paper also presents the precautions to be taken during 70mm MPethe various stages (design, construction & operation) of a HALUL Phase 2project and the feed back after a few years of operation and 2ESndPhs 26h 0m3klessons to be learnt 5 ESP 270hp 70mm2

44km 33kv bPzl2Index Terms - VSDS: Variable Speed Drive Systems, ESP: 185mm2 kmElectric Submersible Pumps, THD: total harmonics distortion, 70mm2Regenerative

PART 1: HOW TO MINIMISE HARMONIC NETWORKPOLLUTION? Figure 1: OFFSHORE PLATFORMS

I. INTRODUCTION II. VARIABLE SPEED ADVANTAGES

Offshore platforms located in the Arabian Gulf have been In general, the use of electronic VSD technology has maindeveloped in association with a well known Middle East Oil advantages, more or less linked:and Gas Company in 3 phases: Flexibility of regulation and functional optimization:

Phase 1 Offshore platforms Central development 1995/1997: * Facility for starting up with a programmable motor torque- 3 Well head platforms equipped with ESP * Flexibility of functionality allowing the adaptation to the- Onshore Treatment train 1 driven machine with variable conditions of use and even

in some cases, to increase its useful duty rangePhase 2 Offshore platforms Eastern development 1999/2001: * Possibility to use motors with a speed higher than

- 2 Well head platforms equipped with ESP and VSD frequency imposed by the network- Onshore Treatment train 2 * Shaft line simplification

Phase 3 Offshore platforms North development 2002/2004: Energetic economy:- a Well head platform equipped with ESP and VSD * Capacity to realise significant energy savings because- a Water separation and injection platform electro mechanical efficiency is intrinsically higher

* Possibility for an equipment to work permanently with theTaking into account that wells are not eruptive it is necessary best efficiency in all the practicable speed ranges and notto activate them with ESP. For phase 1, variable speed drives only in the dimensional maximum duty pointwere not installed for various reasons.

Availability and maintainability:* High availability of equipments due to an improved

reliability and reduced repairs time

* Repair facilitated by modular electronic sub assemblies * 12 or 24 pulses VSDand possibility of implementing automatic fault detection This solution needs an additional and special transformer withprocedures with rapid replacement complex sets of phase shifted AC output windings, the rectifier

Limitation of nuisances and constraints on the bridge of the VSD is design accordingly. So 12 or 24 pulseequipments: VSD is not the appropriate solution for ESP application.

* Reduction of the mechanical constraints (starting uptorque, disconnection, blow of ram, etc.) * Regenerative VSD

* Limited inrush current on the network during motor start This technology was specially adapted for this project and isup developed in the chapter VI.

* Reduction of Starting Power RequirementsIV. PHASE 2: PROJECT DEVELOPMENT STUDIES

For ESP application, the variable speed drive is perfectlyadapted to resolve the following problems: The challenge for this fast track project was to evaluate and

* Unknown Well Productivity determine the most appropriate concept without affecting the* Maintaining Constant Pump Intake Pressure schedule and with a reliability guarantee.* Changing conditions of the well (evolution of the BSW, PI

decreasing, well head pressure) The main technical objectives expected for this project were* Adaptation of the power according to needs determined as following:* Reduction of the constraints on the ESP during the - Voltage variation at the VSD input 10% without any effect

starting up on the motor voltage* Reducing starting power requirements - THD Harmonics limitation 3%* Changing well production conditions over time - No stresses on the motor (electrical and thermal)

- No disturbance in particular for the down hole monitoringl1l. HARMONICS system

Harmonics effects: During the engineering phase, a feasibility study wasSome precautions are required when using VSD's, because performed:electronic devices engender harmonic currents which circulatedue to the impedance of the network, creating harmonic * Network calculationvoltages for other consumers connected to the same network A complete study was pertormed including the choice ofwith the following effects: voltage level, short circuit calculation, stability calculation on

* Motor: additional losses both in the copper and in the the largest equipment starting up, harmonics calculationsiron, these losses create over heating notably in the rotor Due to the fact that the power generation is located 44km farcage away from the platforms, the short circuit power is around

* Oscillating torque produced by the harmonic current, this 30MVA.torque can have harmful effects on the stability and evenon the mechanical resistance if their frequencies are thesame as the rotating frequencies of the shaft line

* Transformers: impure sinusoidal current increase thelosses causing significant overheating and in some t mcases, a resonant circuit is produced

* Cables: increased losses and risk of overheating, nX3damage to cable insulation

* Capacitors: production of resonant circuitsX* Disruption of the regulation devices, remote control, vSD' X

measurements, counters, etc. h 777[

Solutions:* Passive filter

Economic solution, however the filter must be calculated for afixed installed power and a constant harmonic level which is ENanot the case in an ESP application because the number andthe power of equipments in service are always changing; therisk is to destroy the filter. In addition, when the passive filter isstopped, significant pulses affect the network.

* Active filterInteresting solution but the filtering is not completely assured 9i ufor Harmonic current exceeding the capacity of the filter.I

Figure 2: Single line diagram

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ESP sizing DP2 DP3The ESP has been defined for an operating frequency range of Total VSD Power (kVA) 2150 2150between 40 and 60 Hz in order to cover a complete flow range. No filter 12.5% 11.5%

Pump Perfonmance Cure Passive filter 4.9% 4.9%_Variaiyle frequency VSD type regenerative 2.2% 2%

Head

70 Head CapacityHead Capacity With the passive filter option, the size of the filter was more or60 less 500 kVAr by platform for a guaranteed THD less than 5%.50

40 | - - Hz5H V. 6PULSESVSDVERSusREGENERATIVE VSD30 H

40 H > The input stage of a non-regenerative AC drive is usually an20 uncontrolled diode rectifier; therefore power cannot be fed10 << X S X} back onto the AC mains supply. By replacing the bridge diode

____________________ _ hinput rectifier with a voltage source PWM input converter, ACpower supply power flow can be bi-directional with full control

3.00 Motor Loadover the input current waveform and power factor. Current can

2.00 ------------------------------------ now be controlled to give near unity power factor and a lowlevel of line frequency harmonics. An active IGBT converter is

.oe --- --------------------- ---------- used as a sinusoidal rectifier and synchronized with the mainsupply network.

6X 0 1W000 20 3000 3WO 4000 460 60 5600M 6WO 70 76 Furthermore, by maintaining the DC bus voltage above theFigure 3: Pump performance curve in variable frequency peak supply voltage the load motor can be operated at a

higher speed without field weakening. Alternatively, the higherIf the consumed power of the pump is proportional to the cube output voltage available can be exploited by using a motor withof the speed, we have to remember that the motor horsepower a rated voltage higher than the AC mains supply, this reducingoutput rating will increase directly with the ratio of the the current for a given power. REGEN inductors must be usedfrequency. to ensure a minimum source impedance. The difference

between the PWM line voltage and the supply voltage occursacross the regen inductors at the REGEN drive. This voltage

A has a high frequency component, which is blocked by theregen inductor, and a sinusoidal component at line frequency.PUmp absorbdl As a result currents flowing in these inductors are sinusoidal

3M ~~~~~powerMotor sh.aft with a small high frequency ripple.power

0- ~~~~~~~~~~~~~Regenerative main advantages for this applicationE- Low level of harmonics distortion on the main supply: ' 4%- Power factor close to 1

'D 20 40 6 8 - Output voltage can be higher than input voltage (+100 VFrequency (hert) max for 400V of input voltage supply)

Figure 4: ESP power curveIn fact, the input stage of the REGEN is regulated at a higher

As shown on figure 4, the pump requires less HP than the voltage value than the normal voltage value of the 6 PULSE,motor is capable of delivering up to a certain frequency and so this kind of converter is not affected by mains voltagethen exceeds it. fluctuation.

Step up transformer and ESP cable losses Surface packageThe losses have been calculated for the maximum frequency MCCincluding a temperature derating factor LlI THDINetpower<5%

1Ll 2 B

VSD sizing XP21 door panelVSD power was calculated for the maximum surface absorbedpower including the cables and transformer losses l CFiter P IGBTRnverter

Harmonics calculationA compiete study was performed with the most stringent .M444-

conditions (minimum short circuit power minimum, one URFuses ni I33kV/41 5V transformer etc...........) - >' <

IGBTRectiftFerFigure 5: Regenerative structure of the VSD

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Additional necessary equipment Output current

*Sinwave filter (LC type): M6543Ht 03f07104 12.40 ~4 k....5a43HN031004 12:40 Q460(D) 1.9z 1.9% 1.9x AhOl (i)100.0% 2 100.0% 3 100.0 %

LI A389.1 A 382.5A 385.8AMain advantages: +O000, +O00 -00

- Excellent output wave form, reducing the voltage stress on 3

the transformer and/or motor. 0LI LI- Low THD Current.<3%-Elimination of the switching frequency from the VSD, -620 135791 3579122typical range from 2 to 4 kHz.-Elimination of the risk of voltage reflections phenomena RMS THD CF V A VA U `=-E ~-Edue to ESP cable length (2000 to 4000 meters). When the load is increasing during starting of all the wells, the

Step up transformer: ~~~~~total voltage harmonic distortion tends to decrease and these* SteQ u~~~ transformer: ~~tests demonstrated that the THD values are within the lEC and

The output transformer is required to elevate the surface IEEsadrslmt

voltage. The typical voltage required to ESP driving is 2000 upto 4000 V. DP3 HARMONIC

THD-% kWVI. FEEDBACK 3l-5-la3 ~~~~~~~~~~~~~1200

Field tests 2,5 -1000

During the start up of each well, several tests were performed 2-800and recorded as shown in the figure below: the results agree 1,5-600with the harmonics calculations made during the engineering 1 400phase. 0,5 200

Input voltage 0 0

SUVOHZ U~~~~3107YO4 11:86 Q46-k ii... 49S9Hi 03107104 11:59 Q46+ + + + +1.5 %2 2.0 Z 3 1.9 Uh 01 100.Oz% 2 100.Oz 03 100.Oz __________________________________

640V 407.6v 407.5v 407.5v-000,-00, -000,Figure 6: Comparison harmonic and load.

3U %3V 2.03A 3LLI LI~~~~~In terms of absorbed power, we can see that the power factor

12 L21.0 D at the VSD input is close to 1 in all cases.

,t= 5.0m~ U1= +578 U2= -269 U3= -310 13 5 7 1'1 13 1.51'719 21 23 25 VSD INPUTVSDOUTPUTRMS THD CF rmit V A VA U ~-G WELL P(kW) PF P(kW) PF Hz Efcec

Input current 21 167 0,97 151 0,66 46 90,4%22 218 0,98 208 0,74 47,6 95,4%

49.97H~~~~ fl3ffO7V04 1209 k40 ..i ON2z307104 12:10 23 1 56 0,98 1 430,6149,691,7o/5.4z 2 4.1x 5.8z AhOl @100.0% 2 100.Ox 3 100.0 %

300.OA 295.6A 299.3A ~~~~~24175 0,98 160 0,68 443 91,4%+03 0OU oo 28 128 0,98 122 0,67 46 95,3%

3V 5

3L 31 204 0,99 192 0,76 53,4 94,1%0 LI~~~1 LI32.5 L 32 236 0,97 221 0,79 55,5 93,6%

33 134 0,96 119 0,69 46 88,8%4t= 5.0m 11= +441 12= -220 13= -213 3 5 7 911 13 1.5 1'7 1'9 21 23 2.5 ! 34 172 0,971600,70 50,2 93,0%

RMS THD CF ME V A VA U A )36 235 0,98 229 0,75 50,8 97,4%

Output voltage 39 139 0,98 132 0,73 46,9 95,0%20 90 0,95 83 0,55 40,3 92,2%

CK) H fib31O07104 1231i ~46- Jj-. fi.43H 0071C4 12.31 Q46-0 16 09 2 ,44O 192.5 2 2.0 z 3.3 z Uhl011 100.0% 2 100.Oz io0.o 016 096 15 06 4, 19

630V 355.6v 355.5v 356.0Ov 41 168 0,94 157 0,55 40,4 93,5%3-U %

00 00, -0,/3V 10 142 1204 10,97 1189 10,57 144,3 92,6%

RMSTHDCF ~~~ V A VA U ~~~E) A)

Failures These modifications were implemented 5 years ago and thereAs expected with all new technology equipment, some has been no further problem since.problems occurred at the beginning:

VIl. LESSONS LEARNT- Damage to electronic cards and control transformer whena sudden shutdown occurs on the 33kV network. As a result of this technology there has been many application

benefits:The voltage was maintained by the rectifier for a small periodand due to the commutations on the synchronous rectifier the - the VSD input consumes only active energy, whichinput filter was excited and a high amplitude current and reduces the current and the losses in the sub sea cablesvoltage wave occurred at a level higher than the limits of some and in all surface equipments.diodes on electronic cards. - Very low THD Level of harmonics on the network

independent of the short circuit power and the VSD powerThis problem has been analyzed and solved by: - There is no limitation on the implementation of additional

VSD equipment- Voltage clipper and resistance installation upstream of the - It is not necessary to perform harmonics calculations suchcontrol transformers are necessary with active or passive filters solutions

- Modification on interfaces cards - VSD output voltage stresses reduced which result in- Implementation of a new software on the rectifier and increased reliability of cables, motors, transformers

inverter command cards - Reduced magnetic noise on transformer

Following these modifications, there was no reoccurrence ofproblems linked to the VSD.

PART II: ADVANTAGES OF THIS SOLUTIONVoltage before modification ASSOCIATED WITH ATEX MOTORS

15-Ju -0211: 18:108 . INTRODUCTIONA:

R Ms ===== I9 ,/;- 0The aim of PART 11 is mainly to demonstrate the interest of-1i 50 K- new REGEN VSD compared to a typical VSD (6 pulses PWM

inverter) when supplying an ATEX motor.5 Ms _ _ A B

200zo 111. IDENTIFICATION OF CONTRAINTS IN STANDARD-0.60 vl====--======_INVERTER FED MOTOR

C: 3= = = = =

5c3=- ======1 .< It is now commonly admitted that the use of standard inverters-0.606 to drive asynchronous motors may be detrimental to the

_ _------------ _ insulation system. From a motor point of view, there are twoA==------ Il kinds of supplementary stress, compared to a standard 50Hz5 ms~nIr266pV1 AA or 60Hz supply: Thermal and Electrical.-0.60 Y

5 s 7 Firstly, it is well known that an additional temperature rise1 5 UDC x occurs when the motor is fed by an inverter compared to a2 .2 v C 10 D/C normal sine wave supply. This phenomenon can be explained3 .2 V DC DC 0.00 K STPP by the consequence of field weakening and the rich spectra of

voltage harmonics. Indeed, a voltage drop can occur inside theVoltage after modification inverter and the cable length. This can produce generally a

field weakening and for the same torque demanded by the12 Jul 02 shaft, the losses will be increased (Joules and iron losses).A1-------1 This is not acceptable for ATEX standards.

Particular attention must be paid when designing this kind of201.. s A B motor. To avoid this problem the motor designers take into100 1 r|

============___________account the field weakening by decreasing the number ofC:3=========--- winding turns in the slot. In this casew the flux increases and26^ _ _ .Ieev grrnllrrlrrrBwrlllly 1 rI-- compensates the voltage drop stated above. This practice iS

======= I________ currently used for the lower frame sizes, and the flux is_20____________ increased by at least 7% compared to a standard motor.

1n , r 11rr"r^rlt I "n,n +k f/%+n4 I4r% +,+n4 n rx^ T i-rr + L

============__ I_______ IUnfortunately this solution cannot be used In larger motors5 5 DC because of the lower number of turns used. For example a.51 DC 1001 KS/5 400mmfrm sizemor that has turns! lo cannot b3.1 v DC j 1 DC 6.65K frm x oor hsv. ltbE .1 v DC g STOPP[D reduced to 3 turns! slot because the flux will be 33% higher. In

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--this case, a power de-rating is generally used in order to keep 1 DOL 7 2 6 PULSESthe temperature rise at the normal value to comply with the DirectOn Line DRi-VEthermal class of the insulation system. nputItance

The second factor that needs to be taken into account iselectrical stress. Indeed, the use of inverters to drive rotating lmachines may be detrimental to the electrical insulation [1 ] [2]. ,Among the different explanations proposed, the most relevant I /are linked to the existence of over voltages due to external /Xconditions such as large dV/dt, cable length, impedancemismatches between the cable and the motor or to theunbalanced voltage distribution in the winding [3]. Their impact Iis well known. They may trigger Partial Discharges (PD) [4]and lead to a reduction in the life time of the insulation. i

To avoid this second problem an upgraded insulation systemis generally used, particularly in the enameled wire by using a REGENspecial corona resistant wire (Fibber glass wire, etc). In this DRIVEcase the motor is more expensive.One question arises: Is there another way to assure thesecurity and reliability of ATEX motor VSD supplied? Inout

[CL Filter

In the following we will try to answer this questiondemonstrating the benefits of the new approach using aREGENERATIVE inverter.

111. EXPERIMENTAL

The methodology utilized compares both VSD technologies (6PULSES and REGEN) supplying a standard Direct on Line output(DOL) ATEX motor (*) with a normal supply from the main. LC FiIterFocus was on the electrical and thermal points.To achieve this goal a specific test bench was developed andis shown in Figure 7.

(* 90kW4 poles and 400V5OHz)Grid 400V/50Hz IV. RESULTS AND COMMENTS

FLS D 280 - 90 kW- 4 poles - 400V/5OHz EEx d 112G IIB T4

;PaverAnaIyser1 _ _ * Results at Nominal voltage:

DOL 6 Pulses REGENw z

* W Nominal Torque (Nm) 578 577 578n W|DE r VSD Voltage input (Vrms) 400 400,5 401

First harmonic voltage Hi (V) 400,7 400,2 400,4.- = i_ F t l THD input voltage (%) / 2,45 1,4

VSD input current (Arms) / 162 142First harmonic current H1 (A) / 147 141THD Current input (%) / 43 3,7VSD output (Vrms) / 380 415VSD System voltage drop* (Vrms) / / 14Firter output (Vrms) // 401Motor input voltage (Vrms) 400 380 401Motor input current (Arms) 164,8 171 164,6dv/dt motor input (kV4psec) 1,7 E-4 1,75 1,7 E-4

0__ ~~~~~~~~~Voltagepeak motor (Vpk) 577,7 1 115 588Winding temperature rise (K) 70 87,3 71

Figure 7: Specific test bench DE bearing temperature rise (K) 64,9 79,2 64

* VSD system voltage drop: cable + input ifilter + inverter + output filter

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* Results at Nominal voltage minus - 10%: PART Ill

|DOL | 6 Pulses | REGEN | I. OVERALL CONCLUSION

Nominal Torque (Nm) 577 577 577 This new technology presented an important challenge from aVSD input voltage (Vrms) / 360 365 technical and economic point of view. The production of thisFirst harmonic voltage Hi (V) 360 359,6 363 oilfield was strongly linked to the reliability of the equipmentsTHD input voltage (%) / 3,13 1,4 andthe strong impact.VSD input current (Arms) / 174,8 158 and the environing impact.First harmonic current H1 (A) 157,8 162 157THD input current (%) / 36 2,45 The results confirm that this REGEN technology is the mostVSD output (Vrms) / 340 414 adapted for many applications in the Oil and Gas industry.VSD System voltage drop* (Vrms) / / 13Filter output (Vrms) / / 400,7 II. ACKNOWLEDGEMENTSMotor input voltage (Vrms) 360,1 340 400,7Motor input current (Arms) 177,4 186,6 164,8 The authors would like to acknowledge and express theirdv/dt motor input (kV/psec) 1,7 E-4 1,75 1,7 E-4 thanks to their colleagues. There are too many to acknowledgeVoltage peak motor (Vpk) 520,6 1001 578 individually in this paper but there are a few we would like toWinding temperature rise (K) 78 97,5 74 IniiulyIthspprbtheeaeafw ewodlkeoDE bearing temperature rise (K) 77,6 81,6 67,8 specifically mention for their key roles.

From LEROY SOMER:* VSD system voltage drop: cable + input filter + inverter + output filter Christian PETIT - Innovation & development manager

Michel GALAIS - ATEX standard specialistThe results show two main things: Daniel EHANNO - Electrical environment specialist

Fran9ois BOISAUBERT - ATEX standard specialistFirstly, we observe that the temperature rise in the motor is Nicolas DOS SANTOS - Project Manager / Engineering Dpt70K when supplied with 400V sine wave voltage. The motor isdesigned with a good thermal reserve. However, when ll. REFERENCESsupplying the same motor with a standard PMW 6 pulses driveand at the same output torque, the temperature rise increases [1] Y.Shibuya, K.Kimura, H.Mitsui, "Winding insulatingto 87K (97,5K when 360V at the drive input). In the case of the materials degradation under repetitive impulse voltages", onlyREGEN drive, the temperature rise is almost the same as DOL available in French, Cigr6, session 15-104, 1994.at 400V, but decreases at 360V. That means that REGENdrive compensates up to 10% input voltage drop and keeps [2] E. Personn, "Transients Effects in Application of PWMthe flux constant in the motor. In conclusion, from the thermal Inverters to Induction Motors", IEEE Transactions on Industrypoint of view, the REGEN solution drive keeps a constant Applications, Vol 28 n0 5,1095-1101, Sept/Oct 1992temperature rise in the motor even if the input voltagedecreases. [3] A. Bonnett,"Analysis of the Impact of Pulse Width

Modulated Inverter Voltage Waveforms on AC InductionSecondly, the REGEN drive will keep electrical stresses very Motors" Proc. of the Intern. Conf. on Pulp and Paper, 68-75,low due to the output LC filter. The dV/dt is completely 1994flattened and we don't have voltage peaks as in the case of astandard 6 Pulses PWM inverter. The voltage shape is a [4] A.Mbaye, T.Lebey, Bui Ai "Existence of partial dischargescomplete sine wave when a REGEN Drive fed motor. In this in low voltage induction machines supplied by PWM drives",case partial discharges could be not triggered. IEEE Trans.Diel. And El.ns, vol 3, 4,1996

Finally, we have demonstrated that the REGEN solution has IV. VITAtwo advantages for motors: thermal and electrical. This willincreases the life time of the insulation system and also the M. Guy DESCORPS: graduated in France with an electroreliability. Moreover, when using a REGEN inverter we can use technic associated Degree in 1970. He worked for elevena standard design ATEX motor without any problems. years for APAVE a worldwide independent Third Party

Inspection Agency.V. CONCLUSION PART II He joined the electrical Department of ELF in 1983 and TOTAL

in 2000. He has worked as an electrical engineer inThe above results demonstrate the benefits of the REGEN engineering, commissioning and maintenance on several Oil &drive when supplying a standard ATEX motor. This solution Gas Projects throughout the World.complies with the ATEX directives.The subject of this approach is the influence of the type of M. Philippe ESPAGNE: received his degree in mechanicVSD used on the motor temperature rise, the incidence on the technology from Paul Sabatier University, Toulouse France inconstraints imposed when the motor works into an explosive 1980. Since graduation, he has been employed withatmosphere and to help in the evolution of INERIS officials FORASOL Oil&Gas Drilling Company.documents. In 1986, he joined ELF as an electrical engineer involved in

maintenance, commissioning and offshore/onshore

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development project. He is presently employed by TOTAL asSenior Electrical Engineer in Total Head Quarter.

M. Claudiu NEACSU: received the degree of ElectricalEngineering in 1997 from the University Politehnica ofBucharest. He has also working for a Ph.D. at the "Laboratoirede G6nie Electique" of Paul Sabatier University in Toulouse &Leroy Somer. The subject of his doctoral thesis was"diagnostics of the failure in asynchronous motors fed by aninverter". In 2003, he joined the R&D department of LeroySomer at CEB factory.

M. Philippe WESOLOWSKI: graduated in France with a"Genie Electrique" associated Degree in 1985 CNAM.He joined Leroy Somer Company in 1988 as a specialist ofdrive applications in Oil and Gas market.

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