5.5 isolation edcp system 080224

8/3/2019 5.5 Isolation EDCP System 080224

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Newave SA, Switzerland [email protected] - www.newaveups.com28/02/2006 ML3-49 1

ISOLATION IN THE UPSISOLATION IN THE UPS


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Newave SA [email protected] - www.newaveups.com28/02/2006 ML3-49 2

ISOLATIONS IN UPS SYSTEMS

When we speak of UPS isolation it is necessary to be veryprecise in what we understand under isolation in order to avoidmisunderstandings and misinterpretations. There are threetypes of distinct isolations in a UPS System

A) Galvanic Isolation between Input and OutputB) input isolation between Mains and BatteryC) Isolation between the DC-circuit and the UPS Output


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C. DC - Component Output Isolation

a. TRANSFORMER-BASED TECHNOLOGY:

In transformer-based UPS-systems the transformer is usedto step up the voltage at the output of the inverter to avoltage compatible with the utility or generator supplyvoltage. Furthermore it is in the nature of the transformer toisolate DC components and therefore the invertertransformer isolates the DC-circuit from the output load.



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Figure 1 shows the block-diagram of a transformer-based,double conversion UPS-system. It can be seen from thedrawing that the transformer is on the output of the inverter

and not on the output of the UPS.

+

-

NeutralLine connectinginput and output (no

galvanic isolation betweeninput and output)

Inverter Output-Transformer tostep-up output voltage and blocks

DC-component

Static THYRISTORBypass-Switch



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There are two possibilities for the DC-component to pass fromthe UPS to the load when there is an inverter IGBT-fault or a

bypass THYRISTOR fault.

The transformer-based UPS behaves as follows in the two

cases:

a) Inverter IGBT-Fault

b) Bypass THYRISTOR Fault



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a) Inverter IGBT-Fault:

If for example the IGBT 2 of the inverter does not

conduct, a DC-component will be generated and in

the transformer-based UPS the output inverter

transformer will isolate the inverter DC-component

from the load.


F1

F2

IGBT 1

IGBT 2

DC-component due toIGBT fault Transformer blocks DC-

component


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b) Bypass THYRISTOR FaultIf for example one of the THYRISTORS does notconduct, a considerable DC-component will befeeding the load as the transformer does not isolatethe bypass. The transformer-based UPS does NOTcontrol this DC-component .


+

-

THYRISTOR Notconducting

Static Switch DC-component passes uncontrolled tothe load

Inputsine-wave


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C. DC - Component Output Isolation

b. TRANSFORMER-LESS TECHNOLOGY:

As the transformer-less UPS-technology does not provide

an inverter output transformer the DC-component issuemust be handled differently. The DC-component is blockedout the output so that it cannot be fed to the load byhardware and software regulation and control.



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Figure 2: Transformer-less UPS block diagram


b. TRANSFORMER-LESS TECHNOLOGY:

The transformer-less UPS behaves as follows in the two

cases:a) Inverter IGBT-Fault

b) Bypass THYRISTOR Fault


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F1

F2

IGBT 1

IGBT 2

DC-component dueto IGBT fault

Transformer-less

EDCP-SYSTEM:ELECTRONICDC-PROTECTION SYSTEM

for blocking the DC to reach the load

a) Inverter IGBT-Fault:

If for example the IGBT 2 of the inverter does not conduct,

a DC-component will be generated. The transformer-less

UPS-technology handles the DC-component by means of

a fully redundant EDCP-SYSTEM (ELECTRONIC DC-

PROTECTION SYSTEM), so that probability of a DC-component appearing at the inverter output is practically

ZERO !


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b) Bypass THYRISTOR Fault:Furthermore the CONCEPTPOWER is provided with anadditional EDCP-SYSTEM on the bypass side, whichconsists of a SCR-non-conducting-detection-circuit.If one of the static bypass SCRs does not conduct the load

will automatically be transferred to inverter within 2-5msecin order to avoid the DC-component on the load side

DC-Detection and control

system that transfers theload to inverter

+

-THYRISTOR Not

conducting

Static Switch DC-component passesuncontrolled to the load

Inputsine-wave

Transformer-less

EDCP-SYSTEM:

ELECTRONICDC-PROTECTION SYSTEMfor blocking the DC to reach the load


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CONCLUSION:

With the advanced electronic technology the EDCP-SYSTEM isextremely reliable. The probability of a DC-component passing through atransformer-less EDCP-SYSTEM is not higher than a transformer going inshort circuit (and allowing the DC-component to pass).

With EDCP-SYSTEM also on the bypass side of the CONCEPTPOWERTransformer-less technology makes the overall protection from the DC-component on the inverter and bypass side more effective than justthrough a transformer on the inverter side

Furthermore NEWAVE has actually over 25000 3-phase transformer-less

UPS-systems in the market operating and being protected by theEDCP-SYSTEM and we have never had a single case of DC-componentappearing on the load.



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Thank you for your attention

5.5 isolation edcp system 080224

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