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Short-Circuit Current Ratings and AC Drives

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The industry trend for AC drive manufactures to put higher short circuit current marking on AC drives. Recent changes to the NEC and UL 508 have increased industry attention on electrical product’s short circuit ratings. This presentation would discuss how to properly install an AC Drive and to obtain the desired short circuit ratings.

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Short-Circuit Current Ratings and AC Drives

  1. 1. Short Circuit Current Ratings and AC DrivesIvan Spronk, Product Marketing AC DrivesSchneider ElectricIndustry NOW Express
  2. 2. Goal of this session ● Understand ● Importance of proper SCCRs ● Hot button points and confusion about SCCRs ● Be able to articulate the various aspects of SCCRs ● Understand ● The information Schneider Electric provides ● The information most competitors provide ● Be able to position yourself to help your customers ● Know what documents to use to find SCCR for the Altivar product lineSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 2
  3. 3. Why are these ratings important?Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 3
  4. 4. Why are these ratings important to you?● Applying SCCRs properly can: ● Enhance personnel safety ● Limit equipment damage ● Reduce lost production time ● Provide the most cost effective solutionSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 4
  5. 5. Hot Buttons & Points of Confusion ● Recent changes to NEC and UL508 ● Control panels are now required to have a SCCR ● Increased industry attention to SCCRs ● UL 508C: test standard for AC Drives ● Lacks specific test method for short circuit testing ● Leads to different interpretations by manufacturers ● Not all manufacturers publish the same info ● Allows for a “higher must be better” mentality ● Who is impacted the most? ● Those not performing tests on each design: ●System integrators ●Panel builders ●OEMsSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 5
  6. 6. Aspects of SCCRs ● Circuit breakers and fuses ● Designed to operate at some level of short circuit current ● Designed to interrupt current ● Common values: 1k, 5k, 10k, 22k, 42k, 65k 100k ● These are overcurrent protective devices (OCPD) ● Has an AIR rating: ampere interrupting rating ● Other electric equipment panels and products ● UL requirement: ● Have a maximum short circuit current rating ● Designed to operate at some level of short circuit current ● Common values: 1k, 5k, 10k, 22k, 42k, 65k 100k ● Rating can be no higher than lowest rated product ● Equipment and panel need to safely withstand the levelSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 6
  7. 7. Aspects of SCCRs and AC Drives ● Input section ● Available short circuit current has a thermal impact ● True for any device converting AC power to DC power ● Internal section ● Internal of an AC Drive has many current paths ● AC Drives should not be tested like starters ● Output section ● Have IGBTs that turn off at high current level ● Many suppliers provide SCCRs based on testing the outputSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 7
  8. 8. Aspects of SCCRs and AC Drives: Schneider Electric Position● Input section ● Customers need to know the level of available short circuit current the drive was designed to handle● Internal section ● Short circuit testing should test the most vulnerable part● Output section ● A SCCR should not be based on the outputSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 8
  9. 9. Information provided by Schneider Electric: Input Section ● Input Section: ● The input current increases as AFC increases ● AFC = amount of available fault or short circuit current ● True for any devise converting power ● The input AFC rating reflects: ● Available short-circuit current at input terminals that the drive was designed to operate both thermally and electrically ● How much effect do various levels have? ●See Data Bulletin 8800DB0801 for more info ● Schneider Electric designs to UL recommended levels ● Schneider Electric provides this input AFC rating ● If the available prospective short circuit current exceeds the level the drive was designed for, use externally mounted impedance to reduce level – Line reactors are commonly used – DC chokes Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 9
  10. 10. Information provided by Schneider Electric: Internal Section ● Internal Section: ● AC Drives contain many power components ● Diodes ● Capacitors ● IGBTs ● There are multiple paths for a short circuit ● Internal components may short across the power circuit. ● To obtain a SCCR, Schneider Electric performs ● A breakdown of components test ● Testing the most vulnerable parts ● At the marked SCCR value Why do other manufacturers only test and provide a SCCR based on shorting the out put of the drive? Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 10
  11. 11. Information provided by Schneider Electric: Internal Section Electric Company / Distribution Panel ● Why do other manufacturers only test and provide a SCCR based on shorting the output of the drive? ● Left over from the legacy test method for a motor starter ● For a starter or contactor ● Shorting the output tests this entire device ● Many drive manufactures are currently providing a SCCR based on only testing by shorting the output ● Schneider Electric has taken an industry leadership position ● Providing SCCR ratings based on internal breakdown tests ● Leading UL 508C to mandate an internal breakdown tests Load Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 11
  12. 12. Information provided by Schneider Electric● Internal Section: ● Schneider Electric SCCR parameters validated during Breakdown of Components testing ●Contain a breakdown within its enclosure based on the Available Fault Current (AFC) and its listed Overcurrent Protective Device (OCPD) ●Should not create shock, flame, fire or expulsion hazard outside the enclosure ● Schneider Electric provides a rating for a wall mounted AC Drive ● AC drive with optional conduit entrance ● Housing of the unit must contain the hazard ● Schneider Electric provides a rating for an AC drive mounted in an enclosure ●Enclosure around the drive must contain the hazard● See ANNEX document Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 12
  13. 13. Information provided by Schneider Electric: Output Section● Output Section: ● Today’s IGBT technology used by most manufactures ● Will turn off well before fault current builds to dangerous levels – Interrupting 100kA on the output is no issue ● Drive input does not see fault current ● Available input short-circuit current and output interruption rating are unrelated ● Schneider Electric provides this information only to show our product can obtain the same rating on the output ● Testing the output does not help construct a robust solution Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 13
  14. 14. Aspects of SCCRs and AC Drives: our position● Input section ● Customers need to know the level of available short circuit current the drive was designed to handle● Internal section ● Short circuit testing should test the most vulnerable part● Output section ● A SCCR should not be based on the output Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 14
  15. 15. What information do competitors provide? ● ABB provides: ● Input currents with and without line reactors with no explanation ● Specifying expensive Class T fuses only ● No circuit breaker ratings ● Schneider Electric provides: ● Multiple ratings with circuit breakers and GV2 ● Ratings with Class J fuses ● 25-50% less expensive than Class T fusesSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 15
  16. 16. What information do competitors provide? ● ABB ● Claiming maximum 200k SCCR rating ●Clearing relying on testing only the output of the drive ● Claiming actual rating is based on OCPD ● Providing no information about thermal impact of various levels of available fault current ● Schneider Electric provides information about: ● Thermal impact of various levels of available fault current ● Multiple ratings with circuit breakers and GV2 ● Ratings with Class J fusesSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 16
  17. 17. What can you do with this information? ● Assist customers to build equipment that can ● Enhance personnel safety with ratings on product match installation ● Limit equipment damage ● Properly rated to contain a short circuit ● Reduce lost production time ● Properly rated to contain a short circuit ● Provide the most cost effective solution ● Install just what is needed ● Control panel cost is proportional to specified SCCR ● Schneider Electric is leading the industry in this effort by challenging the information being supplied by othersSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 17
  18. 18. Resources Know which Codes & Standards apply to your customer’s equipment ● NEC2011 Article 409.110 and 430.8 ● Requires that industrial control panels be marked with (SCCR) ● Requires AC Drives be rated with a SCCR ● UL508A points to UL508C for power conversion controllers ●i.e. AC & DC power converters or drive controllers ● UL 1995 ● Standard for Air Conditioning and Refrigeration Equipment ● UL508C ● Provides a method of establishing SCCR for Drives ● Provides a SCC rating that satisfies NEC requirements. ● Issues being worked with UL508C ● The standard lags technology changes. ● As such the test methods have room for interpretation. ● Most are publishing only an output short circuit ratingSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 18
  19. 19. Resources ● SCCR ratings for each Altivar product line ● Each product line has a document listing SCCRs ● The Effects of Available Short Circuit Current on AC Drives ● Data Bulletin 8800DB0801 ● Variable Frequency Drives and Short Circuit Current Ratings ● Data Bulletin 8800DB1203 coming soon ● Control Panel Technical Guide ● How to ensure trouble free approval of your UL complaint control panels ● CPTG005_ENSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 19
  20. 20. Summary● Short-circuit ratings allow to: ● Have safer installations ● Minimize equipment damage ● Improve up-time in the most cost effective waySchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 20
  21. 21. A 5HP AC drive…. 40A 5 kA Isc, without Line Reactor, Ipeak=27.2 20A 0A-20A-40A 500ms 510ms 520ms 530ms 540ms 550ms 560ms 570ms 580ms 590ms 600ms I(L1) RMS(I(R8)) RMS(I(L1)) TimeSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 21
  22. 22. A 5HP AC drive…. 60A 22 kA Isc, without Line Reactor, Ipeak=41.7 40A 20A -0A-20A-40A-60A 500ms 510ms 520ms 530ms 540ms 550ms 560ms 570ms 580ms 590ms 600ms I(L1) RMS(I(R8)) RMS(I(L1)) Time Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 22
  23. 23. A 5HP AC drive…. 100 kA Isc, without Line Reactor, Ipeak=62.1 80A 40A 0A-40A-80A 500ms 510ms 520ms 530ms 540ms 550ms 560ms 570ms 580ms 590ms 600ms I(L1) RMS(I(R8)) RMS(I(L1)) TimeSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 23
  24. 24. Altivar 61 AnnexSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 24
  25. 25. ABB ACS355 ● specifying expensive Class T fusesSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 25
  26. 26. ABB ACH550 UH ●Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 26
  27. 27. ABB ACH850 ● now providing Input current with and without line choke ● Class T fusesSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 27
  28. 28. AB PowerFlex 40P ● “actual SCCR = AIC of installed fuse / circuit breaker ● claiming 100k SCCRSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 28
  29. 29. AB PowerFlex 700 ● “actual SCCR = AIC of installed fuse / circuit breaker ● claiming 200k SCCRSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 29
  30. 30. Internal Break Down of Components TestsSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 30
  31. 31. Typical available fault current at various points and appropriate SCCR ratingSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 31
  32. 32. Codes and Standards: UL508C says: 47 Short Circuit Test – High Fault Currents 47.1 When any models within a drive series are intended to be rated with high fault current values in excess of the standard current values required by Table 45.1, then one representative model from those intended to be rated with high fault current values shall be used for testing. This representative model shall be subjected to only one high fault current short circuit test. Exception: A drive series complies with the High Fault Current Short Circuit Test in this section without additional testing when: a) The drive series uses solid state short circuit protection circuitry for compliance with the Short Circuit Test, Section 45; and b) The solid state short circuit protection circuitry is used in accordance with 45.1.3.● Most Drives Manufactures take this exception!● Schneider Electric does NOT● Schneider Electric conducts short circuit testing at the marked short circuit current rating Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 32
  33. 33. UL 508 C: Minimum Short Circuit Test ValuesSchneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 33
  34. 34. Thank You!Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 34

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