DIGATRON Formation Charge Power Conversion Technologies

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Formation Charge Power Technologies Okt-06 Slide 1

An evaluation of formation charge power conversion technologies and

their effect on battery quality and performance

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OverviewGeneral IntroductionIntroduction to charge power conversion technologiesExperimentsResultsConclusion

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IntroductionGeneral

The formation process is still the most time and energyconsuming process when manufacturing batteries.

Formation times have been significantly reduced by batterydesign, the use of addititives and process changes.

The requirement to increase capacity while reducingoperating expenses is a common request.

A goal of any progressive battery manufacturer is to shorten formation time while reducing energy consumed during the process. The requirement to increase capacity while reducing operating expense is a common request. Battery manufactures are looking for innovative solutions from formation system suppliers that provide a competitive edge. That edge may be lower cost to manufacture, improved product quality or some combination of both.

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IntroductionGeneral

There are two leading power conversion technologies used in formation charging rectifiers.

?

Digatron/Firing Circuits formation charging rectifiers provide high current output and allow PC controlled formation processes to take advantage of the efficient cooling methods optimizing the formation processes.

Digatron/Firing Circuits formation charging rectifiers provide high current output and allow PC controlled formation processes to take advantage of the efficient cooling methods optimizing the formation processes.

There are two leading power conversion technologies used in formation charging rectifiers

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IntroductionGeneral

The objective is to evaluate the two power conversion technologies in terms of the following characteristics:

Process efficiency

Crystalline structure of active material

Battery quality and performance

The objective of this paper is to evaluate the two power conversion technologies in terms of the following characteristics:

- Process efficiency- Battery quality and performance- Crystalline structure of active material

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IntroductionSCR Technology

The traditional SCR technology uses phase angle control to regulate DC output.

60A

6A

The traditional SCR technology uses phase angle control to regulate DC output. The DC output signal contains a characteristic 300 Hz current ripple component with an almost constant RMS value within the output range of 10 to 100%.

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SCR Current Ripple

65%

33%22%

13%16%

0%

10%

20%

30%

40%

50%

60%

70%

0,0 0,2 0,4 0,6 0,8 1,0

DC output current (Id) to Full scale DC output current (IdNom)

AC

cur

rent

ripp

le (i r

ms)

to

DC

out

put c

urre

nt (I d

)

SCR

Introduction

For this reason ripple as a percentage of total DC output is greatest at low current levels.

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SCR Power Factor cosφ

0,87

0,70

0,53

0,35

0,18

0,0

0,2

0,4

0,6

0,8

1,0

0,0 0,2 0,4 0,6 0,8 1,0Output Voltage as a Percentage of Full Scale

Pow

er F

acto

r cos

phi

Introduction

There is a direct correlation between power factor and output voltage. When battery string voltage is low with respect to full scale output the power factor will also be low. As battery string voltage increases the power factor improves in an almost linear relationship.

Phase angle control technology requires reactive power which must be compensated for, with Power Factor Correction (PFC) equipment.SCR based rectifiers introduce undesirable harmonics to the AC power line which must be considered when specifing PFC equipment.

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IntroductionIGBT Technology

The IGBT based switch mode technology uses pulse width modulation to regulate DC output.

60A

6A

The IGBT based switch mode technology uses pulse width modulation to regulate DC output.Filter components such as chokes and capacitors of a given package size are significantly more effective when used at 20 kHz than when used in SCR circuits at 300 Hz.

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Current Ripple

33%

65%

22%

13%

16%

0%

10%

20%

30%

40%

50%

60%

70%

0,0 0,2 0,4 0,6 0,8 1,0

DC output current (Id) to Full scale DC output current (IdNom)

AC

cur

rent

ripp

le (i r

ms)

to

DC

out

put c

urre

nt (I d

)

SCRIGBT

Introduction

A characteristic of IGBT circuits is that current ripple is very low, typically less than 1% throughout the output range with worst case ripple at 50% of full scale output and best case at the output extremes.

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Power Factor cosφ

0,87

0,70

0,53

0,35

0,18

0,98

0,0

0,2

0,4

0,6

0,8

1,0

0,0 0,2 0,4 0,6 0,8 1,0Output Voltage to Full Scale Output Voltage

Pow

er F

acto

r cos

phi

SCRIGBT

Introduction

The power factor of IGBT circuits is constant at 0.98 throughout the output range.

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Individual Harmonic Distortion

0,5

25,0

7,5 7,3

2,7 2,81,0 0,8

4,0 3,8

1,5

9,0

4,0 4,0

0

5

10

15

20

25

30

3 5 7 9 11 13 15 17 19 21 23Harmonics

Am

plitu

de [%

]

SCRIGBT

Introduction

This slide displays the individual harmonics at full output for SCR and IGBT circuits. It is obvious that the 5th, 7th and 11th harmonics are the most significant.

Harmonics must be considered when specifing Power Factor Correction equipment.

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IntroductionThis presentation attempts to answering the following common questions:

Is one power conversion technology inherently

more efficient than the other ?better suited to shorten formation time ?

influence battery performance ?Does power conversion technology

influence heat generation in batteries during formation process ?

influence the crystalline structure of active material ?

This presentations attempts to answering the following common questions:


better suited to shorten formation time ?

more efficient than the other ?

Does power conversion technology

influence battery performance ?

influence heat generation in batteries during formation process ?


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OverviewGeneral IntroductionIntroduction of charge power conversion technologiesExperimentsResultsConclusion

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ExperimentsDescription

One formation process was started with DIN EN 630xx truck batteries (130Ah) optimized for cold cranking applicationsusing 6x 60A/360V SCR charge circuits, each circuit 18 batteries and 6x 60A/360V IGBT charge circuits, each circuit 18 batteries

One formation process was started with DIN EN 640xx truck batteries (140Ah) optimized for cycle lifeusing6x 60A/360V SCR charge circuits, each circuit 18 batteries and 6x 60A/360V IGBT charge circuits, each circuit 18 batteries

For each battery type processes were started at the same time with identical programs

One formation process was started with DIN EN 630xx truck batteries (130Ah) optimized for cold cranking applications

using 6x 60A/360V SCR charge circuits, each circuit 18 batteriesand 6x 60A/360V IGBT charge circuits, each circuit 18 batteries.

One formation process was started with DIN EN 640xx truck batteries (140Ah) optimized for cycle life using 6x 60A/360V SCR charge circuits, each circuit 18 batteriesand 6x 60A/360V IGBT charge circuits, each circuit 18 batteries

For each battery type processes were started at the same time with identical programs

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ExperimentsTest to evaluate AC data

AC power net analyzer to evaluate AC data

Battery Manager Formation PC to evaluate DC data

Water bath12 strings each of 18 batteries

Water bath12 strings each of 18 batteries

12x 60A/360V SCR IGBT 12x 60A/360V

One 3-phase power net analyzer was connected to the AC input of the SCR rectifier and another was connected to the AC input of the IGBT rectifier. The analyzer was used to evaluate AC data for real power, reactive power, cosphi and total harmonics distortion (THD).

Battery Manager PC software was used to control the formation process and to evaluate all DC data and electrolyte temperatures

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ExperimentsTest to evaluate battery performanceEvaluation in compliance with DIN EN 50342

Cold crankingCold crankingCold crankingCold crankingCold crankingV10s, t6V

Charge acceptance

Charge acceptance

Charge acceptance

Charge acceptance

Charge acceptance

C, I10min

Capacity C20Capacity C20Capacity C20Capacity C20Capacity C20t10.5V

Cold crankingCold crankingCold crankingCold crankingCold crankingV10s, t6V


Cold crankingCold crankingCold crankingCold crankingCold cranking V10s, t6V


Battery 5Battery 4Battery 3Battery 2Battery 1Data

5 sample batteries per formation batch were selected for test and shipped to an independant battery laboratory. One additional sample was selected for scanning electronic microscope (SEM) analysis.The tests were conducted in compliance with DIN EN 50342.Three cycles were completed consisting of capacity C20 test and a cold cranking test followed by a single charge acceptance test. Data from each 5 sample batch was averaged.

Testing generated 7 data files per batterytimes 5 batteries per test batchtimes 4 formation batches consisting of the following:

- DIN EN 630xx battery formation using SCR rectifier- DIN EN 630xx battery formation using IGBT rectifier- DIN EN 640xx battery formation using SCR rectifier- DIN EN 640xx battery formation using IGBT rectifier

which resulted in 140 datafiles to be evaluated.

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ExperimentsTest to evaluate heat generated during formation

Temperature datalogger

Water baths with 20°C initial temperature

SCR formation circuit IGBT formation circuit

Water baths were filled with 20°C water to establish a common temperature at the start of test.

Separate water baths were used to isolate the test samples from the formation system water bath.

Battery in bath 1 was connected to the formation string of the SCR rectifier.

Battery in bath 2 was connected to the formation string of the IGBT rectifier.

Battery Manager PC software was used to control the formation processes and to monitor electrolyte temperature data.

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OverviewGeneral IntroductionIntroduction of charge power conversion technologiesExperimentsResultsConclusion

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ResultsDC Output Power – 12h Formation Profile

0

20

40

60

80

100

120

140

160

180

18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00

Formation Process Time

DC

Out

put P

ower

[kW

]

This graph represents the DC output power profile generated by the charge regime defined in the Battery Manager program editor.

This profile is identical for both SCR and IGBT circuits.

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ResultsDC Output Power compared to IGBT AC Input Power

0

20

40

60

80

100

120

140

160

180

18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00


Pow

er [k

W]

AC inputDC output

When we compare the DC output power profile to the AC input power profile we see how insignificant the losses are with IGBT technology.

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ResultsIGBT AC Input Power compared to SCR AC Input Power

Daten pflegen

0

20

40

60

80

100

120

140

160

180

18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00


Pow

er [k

W]

IGBT AC inputSCR AC input

When we compare the IGBT AC input power profile to the SCR AC input power profile we can see the efficiency advantage gained with IGBT technology.

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ResultsSCR Real AC Input Power compared to Reactive Input Power

0

20

40

60

80

100

120

140

160

180

18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00


AC

Inpu

t Pow

er [k

W]

Real AC inputReactive AC input

In addition to real power the SCR circuits consume a significant amount of reactive power which will require special power factor correction (PFC).

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ResultsIGBT Energy Counter and Efficiency

kWh07112421 kWh

IGBT efficiency [%]

97,694,285,5

MaximumAverageMinimum

Input AC Energy Counter Output DC Energy Counter

262 kvarhReactive

Real

94,2%

During the 12h formation period the charged energy was 1170 kWh and the real energy consumed was 1242 kWh yielding an average efficiency of 94,2%.

The minimum efficiency of 85,5% occures only during the inital phase of formation when battery string voltage and charge currents are low .

High efficiency is achieved if battery string voltage is above 50% and current is around 75% of full scale output.

Maximum efficiency of 97.6% was recorded at 262V and 44.75A.

Because the reactive power is so low it is not compensated for or considered in this calculation.

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ResultsSCR Energy Counter and Efficiency

kWh07113821 kWh

SCR efficiency [%]

94,691,289,9

MaximumAverage Minimum

Input AC Energy Counter Output DC Energy Counter

0541 kvarh

Real

Reactive 91,2%

During the 12h formation period the charged energy was 1170 kWh and the real energy consumed was 1283 kWh yielding an average efficiency of 91,2%.

The minimum efficiency of 89,9% occures only during the inital phase of formation when battery string voltage and charge currents are low .

High efficiency is achieved at maximum DC power output.

Unlike the IGBT circuits the reactive power is so high and must be compensated for. The inefficiencies associated with PFC compensation are not considered here.

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Results

0,84

0,86

0,88

0,90

0,92

0,94

0,96

0,98

1,00

0,00 0,20 0,40 0,60 0,80 1,00Output Power to Nominal Power

Out

put P

ower

to In

put P

ower

SCRIGBT

Efficiency

The graph compares the measured efficiency of SCR and IGBT powerconversion technologies throughout the DC output power range.

IGBT circuits are up to 5% more efficient than SCR circuits within the output range from 30 to 80%.

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Power Factor cosφ versus output power range

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

0,0 0,2 0,4 0,6 0,8 1,0Output Power to Nominal Power

Pow

er F

acto

r cos

phi

SCRIGBT

Results

The graph compares the measured cosphi of SCR and IGBT power conversion technologies throughout the DC output power range.

The power factor for the IGBT circuit is significantly greater than the SCR circuits throughout the output range and approaches a factor of 1.0 from 40% to 100% of full scale power.

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Power Factor cosφ versus formation process time

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00


Pow

er F

acto

r cos

phi

SCRIGBT

Results

This graph shows the measured power factor for each technology throughout the 12h formation profile.

The average power factor for the SCR was 0,66 and for the IGBT 0,98.

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Results

0

5

10

15

20

25

30

35

40

45

50

18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00


Tota

l Har

mon

ics

Dis

torti

on (T

HD

) [%

]

SCRIGBT

Total Harmonic Distortion versus formation process time

This graph shows the measured total harmonic distortion (THD) for each technology throughout the 12h formation profile.

The average THD for the SCR was 32% and for the IGBT 13%.

With Digatron / Firing Circuits transformer techniques the harmonic characteristic of an SCR rectifier can be reduced down to 20% THD.

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Results

0

10

20

30

40

50

60

70

0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00Formation process time [h]

Ele

ctro

lyte

tem

pera

ture

[°C

]

SCRIGBT

Temperature Formation Profile

24:00

The data collected here goes against the widely held asumption that there is a strong correlation between the output ripple typical of SCR circuits and heat generated during the formation process.

One must conclude that there is no significant difference between SCR and IGBT circuits relating to heat generation during formation for the battery types tested.

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Results

100,00

125,00

150,00

175,00

200,00

225,00

1,00 2,00 3,00

Testcycle

Cap

acity

(cha

rge/

rech

arge

) [Ah

]

SCR DCH SCR CHA IGBT DCH IGBT CHA

C20 capacity test, discharged and recharged capacity

DIN EN 630xx DIN EN 640xx

100,00

125,00

150,00

175,00

200,00

225,00

1,00 2,00 3,00

Testcycle

Cap

acity

(cha

rge/

rech

arge

) [Ah

]

SCR DCH SCR CHA IGBT DCH IGBT CHA

The data here indicates there is no siginificant difference after the third cycle in discharge and recharge capacity for both battery types.

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C20 discharge time down to 10.5V

18 19 20 21 22 23 24 25

3

2

1

Test

cycl

e

Time [h] IGBT SCR

Results

18 19 20 21 22 23 24 25

3

2

1

Time [h]


Again the data indicates there is no significant difference between the two technologies in the C20 discharge test.

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Results

6,00

6,50

7,00

7,50

8,00

8,50

1 2 3

Testcycle

Vol

tage

afte

r 10s

dis

char

ge [V

]

SCR IGBT

Cold cranking test, voltage after 10s discharge

6,00

6,50

7,00

7,50

8,00

8,50

1 2 3

Testcycle


The 10s voltage data during cold cranking provides similar results.

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Cold cranking discharge time down to 6V

0 1 2 3 4

3

2

1

Test

cycl

e

Time [ min] IGBT SCR

Results

0 1 2 3 4Time [ min]


And also cold cranking discharge time to 6V.

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Charge acceptance current after 10 min at 14.4V

0

10

20

30

40

50

60

DIN EN 63013 DIN EN 64001

Battery group

Cha

rge

curre

nt [A

]

SCRIGBT

Results

8,0 Ah8,8 Ah

4,9 Ah5,1 Ah

Unlike the previous tests we do find a significant difference in charge acceptance performance of batteries formed with IGBT circuits.

This data is especially significant due to the small standard deviation in the data collected.

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Crystalline structureResults

SCR IGBTDIN EN130xx

SEM analyzis of the crystalline structure of active material revieled no significant difference in crystal size, quantity and surface area.

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Crystalline StructureResults

DIN EN140xxSCR IGBT

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OverviewGeneral IntroductionIntroduction of charge powerconversion technologiesExperimentsResultsConclusion

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ConclusionAnswers to the following common questions:




Does power conversion technology inherently influence heat generation in batteries during formation process ?

influence the crystalline structure of active mass ?

Based on the test results we can conclude the power conversion technology does not influence formation time.

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ConclusionFormation Process Timedepends on:

48h12h6h

Charg

ing fa

ctor

Final

capa

city

at the

end o

f form

ation

Form

ation

proc

ess

(Coo

ling m

ethod

,

varyi

ng ac

id de

nsity

,

incre

ase o

f cha

rging

curre

nt)


Form

atio

n Pr

oces

s

Form

ation

proc

ess

and

batte

ry ch

emist

ry

(Elec

trolyt

e circ

ulatin

g,

new ad

ditive

s to a

ctive

mate

rial)

Formation process time is determined by:

- charging factor

- final capacity to be achieved during the process as set by themanufacturer

- formation process methods such as cooling, varying acid density,increasing charging currents

- battery chemistry and use of additives

- the reliability of the process control equipment

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ConclusionThis presentation attempts to answering the following common questions:






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ConclusionEnergy cost calculation based on the experiment

1.242 kWh1.283 kWhReal AC energy

+3,8 %Energy cost difference

1.242 kWh1.290 kWhTotal AC energy

94,2 %90,7 %Total efficiency

not required-0.5 %Efficiency losses due to PFC10W/kvar * 130 kvar

IGBT: 259,2 kWSCR: 259,2 kWNominal DC power

94,2 %91,2 %Rectifier efficiency

1.170 kWh1.170 kWhDC energy

The table shows that the SCR circuits will consume 3.8% more energy than an IGBT circuit during the formation process.

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There is no significant difference between SCR and IGBT circuits relating to heat generation during formation for the battery types tested.

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There is no significant difference between SCR and IGBT circuits relating to battery performance except charge acceptance for the battery types tested.

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SEM analyzis of the crystalline structure of active material revieled no significant difference in crystal size, quantity and surface area.

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ConclusionUltimately it is the goal of this presentation to reduce the test results and conclusions to a set of practical guidelines that can be applied by battery manufacturers when making decisions regarding the selection and purchase formation rectifier equipment.

The test results indicate there is no significant advantage to either SCR or IGBT technology when considering key factors including process control, battery quality or battery life. That given one must consider the financial aspects when making a purchase decision.

If your formation line includes SCR rectifiers with significant service life remaining there is no financial justification for replacement with IGBT. The 3-5% energy savings with IGBT will not result in positive return on investment in the near term. If your local utility has required PFC that investment has already been made and cannot be recouped. Maintenance personnel are already quite familiar with SCR technology, PM procedures, repair processes and typically there has been a significant investment in spare parts inventory that would not be compatible with IGBT rectifiers.

If your formation line includes IGBT rectifiers we recommend continuing with this technology. There is the benefit of energy savings and you will avoid the need for additional PFC equipment when increasing capacity. If your objective is to outfit a new facility we recommend you consider IGBT technology for the same reasons.

Ultimately it is the goal of this presentation to reduce the test results and conclusions to a set of practical guidelines that can be applied by battery manufacturers when making decisions regarding the selection and purchase formation rectifier equipment.

The test results indicate there is no significant advantage to either SCR or IGBT technology when considering key factors including process control, battery quality or battery life. That given one must consider the financial aspects when making a purchase decision.

If your production line includes SCR rectifiers with significant service life remaining there is no financial justification for replacement with IGBT. The 3-5% energy savings with IGBT will not result in positive return on investment in the near term. If you local utility has required PFC that investment has already been made and cannot be recouped. Maintenance personnel are already quite familiar with SCR technology, PM procedures, repair processes and typically there has been a significant investment in spare parts inventory that would not be compatible with IGBT rectifiers.

If your formation line includes IGBT rectifiers we recommend continuing with this technology. There is the benefit of energy savings and you will avoid the need for additional PFC equipment when increasing capacity. If your objective is to outfit a new facility we recommend you consider IGBT technology for the same reasons.

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Conclusion

Standard current ranges from 30A to 60A Voltage ranges up to 440VDCUp to 16 circuits in one cabinetEfficiency up to 98%Power factor up to 0,98Isolated secondary for each circuit to eliminate circuit interaction and for safetyParalleling of circuits for higher current outputConstant current pulse discharge and depolarization discharge

Digatron/Firing Circuits is a leading supplier of both SCR and IGBT formation rectifiers. SCR rectifiers have been furnished tohundreds of battery manufacturers worldwide over more than three decades.

Our first installation of IGBT rectifiers was commissioned some 8 years ago and has proven extremely reliable.

Technical data for IGBT rectifiers is as follows:

Digatron/Firing Circuits is a leading supplier of both SCR and IGBT formation rectifiers. SCR rectifiers have been furnished to hundreds of battery manufacturers worldwide over more than three decades.

Our first installation of IGBT rectifiers was commissioned some 8 years ago and has proven extremely reliable.

Technical data for IGBT rectifiers is as follows:

Standard current ranges from 30-60A, other ranges available

Voltage output to 440VDC

Up to 16 circuits in a cabinet

Efficiency up to 98%

Power factor up to 0.98

Isolated secondary for each circuit to eliminate circuit interactionand enhance safety

Paralleling of circuits for higher current output

Constant current pulse discharge and depolarization discharge

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DIGATRON Formation Charge Power Conversion Technologies

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