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.

1. Short Circuit Current Ratings and AC Drives
Ivan Spronk, Product Marketing AC Drives
Schneider Electric
Industry NOW Express

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 line
Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 2

3. Why are these ratings important?
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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 solution
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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
●OEMs
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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 level
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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 output
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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 output
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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
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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?
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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
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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
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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
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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
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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 fuses
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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 fuses
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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 others
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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 rating
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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_EN
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20. Summary
● Short-circuit ratings allow to:
● Have safer installations
● Minimize equipment damage
● Improve up-time in the most cost effective
way
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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))
Time
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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. 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))
Time
Schneider Electric - Industry Business – Short Circuit Current Ratings and AC Drives – 2012 23

24. Altivar 61 Annex
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25. ABB ACS355 ● specifying expensive Class T fuses
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26. ABB ACH550 UH
●
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27. ABB ACH850
● now providing Input current
with and without line choke
● Class T fuses
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28. AB PowerFlex 40P
● “actual SCCR = AIC of
installed fuse / circuit
breaker
● claiming 100k SCCR
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29. AB PowerFlex 700 ● “actual SCCR = AIC of installed
fuse / circuit breaker
● claiming 200k SCCR
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30. Internal Break Down of Components Tests
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31. Typical available fault current at various points
and appropriate SCCR rating
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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
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33. UL 508 C: Minimum Short Circuit Test Values
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34. Thank You!
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