vfd commissioning dept

7/31/2019 VFD Commissioning Dept

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WELCOME TO APRESENTATION ON

LCI TYPE VFD- BY COMMISSIONING GROUP

PROFESSIONAL CIRCLE


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INTRODUCTION


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WHAT IS A VFD ?

VFD means Variable Frequency Drive, i.e.,adjustable speed AC motor drive system to

control and/or optimize processes.

AC Line frequency power is converted to DC& again inverted to AC power of required

frequency to be applied to the motor stator to

get speed as per process requirement.

AC to DC conversion & again DC to AC

inversion are done by semiconductor devices

(this case it is Thyristors) & electronic control.


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There are different methods of

adjustable speed system such asCycloconverter, phase-controlled

switches, stator power control of

synchronous motor with Load-commutated inverter system (LCI).

LCI drive system is most effective &

common in compressor, pump & fan

applications


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WHAT IS LCI ?

LCI means Load Commutated Inverter.

Commutation is the process whereby

changing voltage cause one cell to stop

conducting and another to begin.

In Other words Control can turn ON a

thyristor, but we need the changingvoltage relationship to turn it OFF

Commutation takes place.


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WHAT IS LCI ? In case of rectifier bridge, the power system

provides the voltage & energy for commutation,so it is called a line commuted bridge

In case of Inverter bridge, the requirement is

same , but a synchronous motor with leadingpower factor ( current leading voltage) shall be

able to provide the voltage (back e.m.f of the

motor) & energy for commutation. Hence, the

Load (Synchronous machine) helpscommutation required for inverting DC to AC.

That is why it is called Load commuted

inverter.


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Why a synchronous motor, not an

induction motor IN LCI?

A synchronous machine is used

because of its ability to deliverleading VARs which commutate

the inverter bridge. And

induction motor cannot do this.


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LCI TYPE VFD

LCI type VFD can be either 6-pulse single

channel type or 12-pulse dual channel type . Each

channel consists of an isolating transformer,

source converter, DC link inductor and loadconverter, in a single channel type VFD, the

synchronous motor will have one winding

whereas in dual channel type VFD, the

synchronous motor will have two windings, one

for each channel. The source side converter

operates in rectifier mode whereas the load side

converter operates in inverter mode.


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The DC link inductor effectively isolates load

side frequency and source side frequency and

smoothens the DC link current.

The demand signal received from the control

system prompts the source side converter to

provide the required current to the DC link

inductor at the DC voltage level set by the load

side converter. Thus the source side converter

plus the DC link inductor become currentsource controller to the motor and the motor

torque, frequency (hence speed) and voltage

level get adjusted to the load requirements.


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he choice of six pulse, single channel, or 12

pulse dual channel VFD depends on the.

Harmonics that are allowed to beinjected into the grid

Whether redundant fan/pump isavailable.

2-pulse system is recommended where lower


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--Saving in operational cost due to reduced power

consumption .

-- Absence of voltage dip problems associated with DOL

starting of large motors since the starting current in this driveis limited to about 120% of the motor full load current (soft

start).

-- Increased motor life due to the lower thermal andmechanical stresses in view of the absence of starting inrush

currents(6-7 times FLC) , reduced speed operation.

-- No limitation on the number of starts.

ADVANTAGES OF LCI TYPE

VFD


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VARIABLE FREQUENCY DRIVES :VARIABLE FREQUENCY DRIVES :

APPLICATION AREASAPPLICATION AREAS

LCI HSLCI IMD

BOILER ID/FD/PA FANS X - X

GAS TURBINE STARTER X - X

COMPRESSOR / BOILER FEED

PUMPX X X

EXTRUDER / MIXER X - X

BOILER CONDENSATE PUMP X - X

CIRCULATING WATER PUMP X - X

CEMENT MILL FAN / PIPELINE

PUMPSX X X


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VARIABLE FREQUENCY DRIVES :VARIABLE FREQUENCY DRIVES :

APPLICATION AREASAPPLICATION AREAS

LCI HSLCI IMD

HIGH SPEED BLOWERS /

PUMPS- X -

SLURRY PUMPS / SEWAGE

PUMPSX - X

FREQUENCY CONVERTER /

MOTOR STARTERX - -

X = SYSTEM SUITABLE AND APPLICATION

DATA AVAILABLE

- = SYSTEM NOT SUITABLE AND / ORAPPLICATION DATA NOT AVAILABLE


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RATINGS AVAILABLE with BHEL Design :RATINGS AVAILABLE with BHEL Design :

LOAD COMMUTATED INVERTER : 1000 KW TO 15000

KW

HIGH SPEED LOAD COMMUTATED : 4500 KW TO 45000

KW INVERTER

INDUCTION MOTOR DRIVE : 150 KW TO

2000 KW


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6 PULSE CONVERTER6 PULSE CONVERTER


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CONVENTIONAL BOILER FEED PUMPCONVENTIONAL BOILER FEED PUMP

GEAR BOX +

HYDRAULIC

COUPLING

INDUCTION

MOTOR

BOOSTER

PUMP

INDUCTION MOTOR

150KW

SUPER

SYNCHRONOUS

MOTOR

BOILER

FEED

PUMPVFD

UPTO

100 Hz

50 Hz GRID

50 Hz GRID

ARRANGEMENT WITH VFDARRANGEMENT WITH VFD

BOOSTER

PUMP


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TECHNO-ECONOMIC ANALYSIS OF 6 PULSE VFD OVER HYDRAULICTECHNO-ECONOMIC ANALYSIS OF 6 PULSE VFD OVER HYDRAULIC

COUPLING FOR 250MW BOILER FEED PUMP DRIVESCOUPLING FOR 250MW BOILER FEED PUMP DRIVES

MOTOR RATING: 3900 KW ,5300 RPM NO.OF PUMPS PER BOILER :3MOTOR RATING: 3900 KW ,5300 RPM NO.OF PUMPS PER BOILER :3

SL. GEN ENERGY CONSUMED ENERGY PAYBACK

NO. MW PER Yr IN MW.Hr SAVED DUE PERIOD

HYD. VFD TO VFDCOUP.

1. 150 9000 7575

2. 200 10426 9101 9.39 6YrsMILLION Rs

3. 250 12423 11415


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RECTIFIER INVERTER

REACTOR

BRUSH

LESS

Exciter

SYNC.

Motor

AC Line

DC Link

1 3 5

4 6 2

2 6 4

135


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2

5

6 4

3 1

Fld.WdgExciter

Phase

controlle

d

switches

415 V Power

LCI BRUSHLESS EXCITER

Exciter is an induction

frequency changer


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EFFECIENCY CURVE OF VARIOUS FLOW

CONTROL DRIVES

100 % Efficiency

80

60

40

20

0 20 40 60 80 100

% Speed / Flow

Hydraulic Coupling

Inlet Guide Vane

Outlet Damper Throttling

LCI or VFD Drive


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CONTROL SYSTEM

AC MACHINE TORQUE EQUATION

T = (1/w)*q*E*I*cos

q = no.of phases in armature winding

E = r.m.s induced voltage of armature

I = r.m.s current per phase of armature

= phase angle between E & I

w = mechanical angular velocity is related to electrical angularvelocity by 4**f / p , p = no.of poles, f = frequency.

So, T E*I*cos / f , that is * I * cos


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CONTROL SYSTEM

The speed reference from the process controller is a

compared to a speed feedback derived from theintegrated motor voltage & error is fed to a speed

regulator.

The output of speed regulator is a torque command.

This torque command is sent to the field controller and

to a current controller as a current command.

By proper control of stator current & field excitation ,

the machine has a fairly linear torque-per-ampere

characteristic.

The most straight forward approach is a speed controller

with a V/f controller for field excitation.


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CONTROL SYSTEMThere are three controllable element which can

be used to control the power to the motor:

- The source side converter

- The load side converter

- the field exciter.

All three of these use phase control of thyristor

gating angle to control output.

Major function of load side converter control is

to keep the power to the motor at the highest

possible power factor.


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CONTROL SYSTEM

A current feedback signal is derived from theAC current into the source side power

converter.

The output of the current controller is used to

control the gate firing angle of the source side

converter to adjust the DC link voltage

necessary to produce the commanded current.


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How much power saving? A case study

Site: TATA POWER, TROMBAY, 500 MW Units

SITUATION: UNIT 5 with Flue gas controlled by

dampers

UNIT6 Flue gas controlled by VFD

Power consumption of ID fans in both the units were

taken at various generating points and data isoutlined in TABLE 1

H h i ? A d


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TABLE 1

Gen.MW

U5IDsTotalPower (KW)

U6 Total power(KW) by IDFans

Power Saving

200 3800 850 2950

240 4150 950 3200

280 4450 1050 3100

320 4800 1250 3550

360 5050 1420 3630

400 5350 1850 3500

440 5600 2500 3100


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From table1 it is seen that power saving

ranging from 2900 KW to 3630 KW at various

gen. Points

Considering an average saving of 3200MW

and 300 days in operation a net saving of

Rs.288 lakhs @ generating costRs.1.25/unit

Capital investment on VFD Rs.500 Lakhs

Payback period less than 02 years.


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Techno-economical analysis for use of VFDsfor BFPs in 210MW units

Situation : Constant pressure operation

Motor rating: 3500KW, 5300 R.P.M

No.of pumps in a boiler: 3

VFD design: 6 pulseExisting coupling: Hydraulic

Parameters on both the case maintained same

H h i ? A t d


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How much power saving? A case studySl.no Hydrau.coupling VFD system

MCR (%) 60% 80% 100% 60% 80% 100%

Speed rpm 4459 4596 4815 4459 4596 4815

Flow t/h 1780 1860 1965 1780 1860 1965

1 Power drawn bytwo BFPs(KW)

3750 4344 5176 3106 3742 4706

2 Energyconsumed MWhin a yr.

31849 ( considering2400 hrs. operation on eachMCR rating)

28091( considering 2400hrs. operation on each MCRrating)

3 Running cost atRs. 1.25/KWh

398.11 lacks 351.14 lakhs

4 Saving in cost 46.97 lacks/yr.

5 Additional cost

during initial

150 lackhs


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LATEST DEVELOPMENTS IN VFDsLATEST DEVELOPMENTS IN VFDs

IGBT POWER CIRCUIT FOR INDUCTION MOTOR

DRIVES (LACKING IN POWER STATION

EXPERIENCE )

UNITY INPUT POWER FACTOR

MINIMUM INPUT HARMONICS

ALMOST SINE WAVE OUTPUT

SELF TUNING CONTROLLER

DC MOTOR LIKE CONTROL CHARACTERISTICS


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BHEL VFD FORID FANS OF 500

MW UNITS : AN

OVERVIEW


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Panels related to VFD in VFD room

C on trol Pa n

(all externalinterlocks,

alarm s, Pow

supplies

available her

C& E Sectio

(C on trol anexcitation)

Bridge

blow er &Filter

section

LCI,

Section(Converte

& Inve ste

bridges)

Load

breaker (V C B )

Com m on for both chanels in one I

Fans , but interlock ing & tr ip relay

seperately m ounted in this panel f

each c hannel

LCI Panel


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C & E (Control & Excitation) Panel

PSFF

Power

Supplymodule

70V

Gate

Supplymodule

Exciter

Module

SEM Rack

(Microprocesso

& other controlcards)

IOM A

(Input / outputmodule)


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Fan & Filter Panel

AIR

FAN 1

FAN 2

Filter Resistors

and capacitors

Air flow

monitor

sensor


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H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

H P T K X P T N

S

T

M

1

S

T

M

3

S

T

M

5

L

T

M

4

L

T

M

6

L

T

M

2

S

T

M

4

S

T

M

6

S

T

M

2

L

T

M

1

L

T

M

3

L

T

M

5

STM - Source Thyristor Module

LTM - Load Thyristor Module

HPTK - Gate firing card

XPTK - Attennator fead back card

LCI (Load

Commuted

Inverter)

Thyristor

Bridge


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NOTE: In each Thyristor stack there are

three Thyristors in series. Each Thyristor ishaving one indication card with neon lamp.

In case of Thyristor short circuit this neon

lamp will not glow. One Thyristor shortcircuit in a stack is allowed. If two

Thyristors get shorted load / source

commutation failure will arrive dependingupon which thyristors have failed and

channel will get tripped.


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ControlControl

Cooling Fan Cooling Fan

INTER

FACE

INTER

FACE

REACTO

CONTROL &

EXCITA TION

PANEL

CONTROL &

EXCITA TION

PANEL

INTER

FACE

INTER

FACE

REACTO

Control Control

Cooling FanCooling Fan

UA

11kV

B US

UA

11kV

BUS

Transforme

11/ 2.3KV

(D yn), 3kvA

Transforme

11/ 2.3KV

(Ddo), 3kv

ID Ch #

415V 3 Phase

supply form ES

415V 3 Phase

supply form ES

Source

breake

Source

breake

ID Ch # POW ER CONVE RTER BRID

POW ER CONV ERTER BRID Loadbreake

Load

breake

BRUSHLESS

SYNCHRONO

MOTOR

Channel 1

Channel


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THYRISTOR FIRING

1 53

2

1

4 66 2

1 2 3 4 5 6 1 2 3

120 de .


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1 3

4 6

5

2

I

DC

Voltage

Source

Synchronous Motor

Stator Winding

R Ph

Y Ph

B Ph


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1 3

4 6

5

2

I

DC

Voltage

Source

Synchronous Motor

Stator Winding

R Ph

Y Ph

B Ph


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1 3

4 6

5

2

I

DC

Voltage

Source

Synchronous Motor

Stator Winding

R Ph

Y Ph

B Ph


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1 3

4 6

5

2

I

DC

Voltage

Source

Synchronous Motor

Stator Winding

R Ph

Y Ph

B Ph


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1 3

4 6

5

2

I

DC

Voltage

Source

Synchronous Motor

Stator Winding

R Ph

Y Ph

B Ph


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1 3

4 6

5

2

I

DC

Voltage

Source

Synchronous Motor

Stator Winding

R Ph

Y Ph

B Ph


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1 3

4 6

5

2

I

DC

Voltage

Source

Synchronous Motor

Stator Winding

R Ph

Y Ph

B Ph


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R Ph

Y Ph

B Ph

1 2 3 4 5 6 1

FIRING SEQUENCE & PHASE CURRENTS


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VFD Data for Motor:

Base armature current per channel - 580

AmpsBase Voltage(Ac r.m.s) - 2300 V

Base speed / frequency - 530 / 44.2

Base exciter current - 150 Amps

Exciter Data:

Rated EVC Current - 74 Amps

Maximum allowable continuous exciter stator currentat standstill: - 75 Amps

Nominal source voltage - 2300 V AC


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Source breaker tripping initiated through VFD

system:

This is other than protection tripping from HT

S.W.gear)

Source breaker tripping through an aux.

relay (hand resettable flag relay) mounted on

control panel. VAA13 relay on each channel.

In case of source breaker tripping check this

relay has operated on control panel of VFD

room. If this relay has not operated tripping is

from HT breaker tri circuit rela s &


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VAA13 relay can operate on following

conditions:

Through LCI panel source side faultthrough SWGR relay in LCI panel.Through 11KV/2.3KV transformer Oil

temp. trip, winding temperature trip &Buchholz trip. In that case flag relay

(FLAGRY) installed just above VAA13 relay

shall operate & flag will come.

Emergency push button is pressed.Trip command from control panel

[CLOSE-NEUTRAL-TRIP] on VFD room.


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POWER SUPPLIES

In control panel of VFD room there are

following supplies for different

interlocks & distribution:-1.0 3Phase, 415 V AC supplies

02Nos. (1st from Ch # 1 LCI Panel &

2nd from Ch # 2 LCI Panel) which inturn fed from 415V ESP MCC.


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415 V AC supplies stepped down to 110V

AC, 1phase and 220 V AC, 1phase supplies

through transformers.110V supply used for control & interlock

relays of both channels in control panel itself.

220V supply is used for space heaters ofpanels, motor, reactor, cubicle illumination

lamps, door mounted printer and line

drivers, temperature scanner, reactor temp.indicator, motor water leakage defector etc.


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24V DC: 24V AC stepped down from

415V and then rectified to 24V DC for

control panel indication lamp.

Another 24V DC supply from FSSS for

starting / stopping circuit of ID Fan

channels.

220V DC: supply from station battery

supply for source breaker tripping

interlocks.


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Power supplies in LCI Panel:

. 2.3 KV main supply connected to Source Bridge inbridge panel.

. 415 V 3 phase supply to C&E panel which is drawn

from ESP feeder (separate source for each C&E panel forCh # 1&2).

415V supply stepped down to 220V & 110V AC

220V, 10 AC is used for fan flow indicator & SEM rack

fan.

110V AC, 1phase is used for power supplies to all


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SOME MAJOR FAULTS: VFD trips on these faults

Loss of cooling fan

Source Overcurrent

Load overcurrent

Field Loss

Load commutation failure

Source commutation failure

Load overvoltage fault

Bridge differential pressure

Gating supply undervoltage fault

P105 supply undervoltage

SOME MAJOR FAULTS VFD t i th f lt


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SOME MAJOR FAULTS: VFD trips on these faults

Overspeed

Ground Fault

Fan compartment door open

Source Low line or deep undervoltage

SOME MAJOR ALARMS: Attention needed to check

Loss of speed reference

Gating supply undervoltage

Microprocessor alarm

Bridge filter fuse blown

Source undervolts

Transformer alarm


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START PERMISSIVES FOR THE CHANNELS (To be seen

at VFD room):

No emergency stop pressed.

No motor overtemperature trip persisting

Bus supervision 24V DC & 220V DC healthy

Heating & Illumination CB 2 ON

No water leakage in Motor

Water flow healthy in motor

CB3 in control panel ON, all indication lamp circuit healthy

No transformer alarms persisting

No transformer trips persisting


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START PERMISSIVES FOR THE CHANNELS (To be seen

at VFD room):

No reactor alarm persisting

No reactor trip persisting

Motor isolator i.e., VFD breaker (VFD output to motor) not

closed

Source breaker closed


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CLOSE PERMISSIVES FOR THE SOURCE BREAKER

(To be seen at VFD room):

No emergency stop pressed.No motor over temperature trip persisting


Heating & Illumination CB 2 ON

No water leakage in Motor

Water flow healthy in motor

CB3 in control panel ON, all indication lamp circuithealthy

No transformer alarms persisting

No transformer trips persisting


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CLOSE PERMISSIVES FOR THE SOURCE BREAKER

(To be seen at VFD room):

No reactor alarm persistingNo reactor trip persisting

Permit to close source breaker from LCI panel ( from

IOMA card : Swgr. Relay shall not be picked up


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CHANNEL RUN PERMIT (To be seen at VFD room):

No emergency stop pressed.

No motor over temperature trip persisting


Heating & Illumination CB 2 ONNo transformer trips persisting

No reactor trip persisting

Source breaker closed

Motor isolator i.e., VFD breaker (VFD output to motor)

not closed


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THANK YOU

vfd commissioning dept

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