|        |
|--------|
|        |  |  |  |  |
|   |   |   |   |   |

|             |
|-------------|
|             |  |  |  |  |
|        |   |   |
| Form 10-K/A |
|        | (Amendment No. 1) |   |

|        |
|--------|
|        |  |
| ý | ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

|        |
|--------|
|        |  |
|  ̈ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

|                                                                                           |
|-------------------------------------------------------------------------------------------|
|                                                                                           |  |  |  |  |
|                                                                                      |   |   |   |   |
| American Superconductor Corporation(Exact Name of Registrant as Specified in Its Charter) |
|                                                                                      |   |   |

|                                                               |
|---------------------------------------------------------------|
|                                                               |  |  |
| Delaware                                                      |   | 04-2959321 |
| (State or Other Jurisdictionof Incorporation or Organization) |   | (IRS EmployerIdentification Number) |
|                                                          |   |   |
| 114 East Main StreetAyer, Massachusetts                       |   | 01432 |
| (Address of Principal Executive Offices)                      |   | (Zip Code) |

|                                                                      |
|----------------------------------------------------------------------|
|                                                                      |  |  |  |  |
| Securities registered pursuant to Section 12(g) of the Act:None |
|                                                                 |   |   |   |   |

----

|                                   |
|-----------------------------------|
|                                   |  |  |  |  |
| Large accelerated filer |  o |   | Accelerated filer |  x |
|                              |   |   |   |   |
| Non-accelerated filer        |  o | (Do not check if a smaller reporting company) | Smaller reporting company |  o |
|                              |   |   |   |   |
|                              |   |   | Emerging growth company |  o |

|        |
|--------|
|        |  |  |  |  |
|   |   |   |   |   |

----

----

|               |
|---------------|
|               |  |  |  |  |  |  |  |  |  |  |  |  |
|          |   |   |   | Incorporated by Reference |
| ExhibitNumber |   | Exhibit Description |   | Form |   | File No. |   | Exhibit |   | FilingDate |   | Filed/FurnishedHerewith |
| 3.1           |   | Restated Certificate of Incorporation of the Registrant, as amended. |   | S-3 |   | 333-191153 |   | 3.1 |   | 9/13/2013 |   |   |
| 3.2           |   | Certificate of Amendment of Restated Certificate of Incorporation of the Registrant, dated March 24, 2015. |   | 8-K |   | 000-19672 |   | 3.1 |   | 3/24/2015 |   |   |
| 3.3           |   | Amended and Restated By-Laws of the Registrant. |   | S-3 |   | 333-191153 |   | 3.2 |   | 9/13/2013 |   |   |
| 4.1           |   | Amended and Restated Warrant Agreement, dated as of December 19, 2014, between the Registrant and Hercules Technology Growth Capital, Inc. |   | 8-K |   | 000-19672 |   | 4.1 |   | 12/22/2014 |   |   |
| 4.2           |   | Form of Indenture, between the Registrant and Wilmington Trust, National Association. |   | S-3 |   | 333-198851 |   | 4.1 |   | 9/19/2014 |   |   |
| 4.3           |   | Form of Warrant Agreement, by and between the Registrant and the American Stock Transfer and Trust Company, dated November 13, 2014, and Form of Warrant. |   | 8-K |   | 000-19672 |   | 4.1 |   | 11/13/2014 |   |   |
| 10.1+         |   | 2007 Stock Incentive Plan, as amended. |   | 8-K |   | 000-19672 |   | 10.1 |   | 8/2/2016 |   |   |
| 10.2+         |   | Form of Incentive Stock Option Agreement under 2007 Stock Incentive Plan, as amended. |   | 8-K |   | 000-19672 |   | 10.2 |   | 8/7/2007 |   |   |
| 10.3+         |   | Form of Non-statutory Stock Option Agreement under 2007 Stock Option Plan, as amended. |   | 8-K |   | 000-19672 |   | 10.3 |   | 8/7/2007 |   |   |
| 10.4+         |   | Form of Restricted Stock Agreement Regarding Awards to Executive Officers under 2007 Stock Option Plan, as amended. |   | 8-K |   | 000-19672 |   | 10.4 |   | 8/7/2007 |   |   |
| 10.5+         |   | Form of Restricted Stock Agreement Regarding Awards to Employees, under 2007 Stock Option Plan, as amended. |   | 8-K |   | 000-19672 |   | 10.5 |   | 8/7/2007 |   |   |
| 10.6+         |   | Form of Restricted Stock Agreement (regarding performance-based awards to executive officers and employees) under 2007 Stock Incentive Plan, as amended. |   | 8-K |   | 000-19672 |   | 10.1 |   | 5/20/2008 |   |   |
| 10.7+         |   | Amended and Restated 2007 Director Stock Plan. |   | 8-K |   | 000-19672 |   | 10.2 |   | 8/2/2016 |   |   |
| 10.8+         |   | Form of Non-statutory Stock Option Agreement Under Amended and Restated 2007 Director Stock Plan. |   | 8-K |   | 000-19672 |   | 10.7 |   | 8/7/2007 |   |   |
| 10.9+         |   | Executive Incentive Plan for the fiscal year ended March 31, 2017. |   | 10-Q |   | 000-19672 |   | 10.1 |   | 8/9/2016 |   |   |
| 10.10+        |   | Executive Incentive Plan for fiscal year ended March 31, 2018. |   | 10-Q |   | 000-19672 |   | 10.1 |   | 8/8/2017 |   |   |

----

|               |
|---------------|
|               |  |  |  |  |  |  |  |  |  |  |  |  |
|          |   |   |   | Incorporated by Reference |
| ExhibitNumber |   | Exhibit Description |   | Form |   | File No. |   | Exhibit |   | FilingDate |   | Filed/FurnishedHerewith |
| 10.11+        |   | Form of Employee Nondisclosure and Developments Agreement. |   |   |   |   |   |   |   |   |   | ** |
| 10.12+        |   | Amended and Restated Executive Severance Agreement, dated as of May 24, 2011, between the Registrant and Daniel P. McGahn. |   | 8-K |   | 000-19672 |   | 10.2 |   | 5/24/2011 |   |   |
| 10.13+        |   | Amended and Restated Executive Severance and Consulting Services Agreement, dated as of June 30, 2017, between the Registrant and David A. Henry. |   | 8-K |   | 000-19672 |   | 10.1 |   | 7/3/2017 |   |   |
| 10.14+        |   | Amended and Restated Executive Severance Agreement, dated as of September 20, 2013, between the Registrant and James F. Maguire. |   | 8-K |   | 000-19672 |   | 10.1 |   | 9/25/2013 |   |   |
| 10.15+        |   | First Amendment to Amended and Restated Executive Severance Agreement, dated April 6, 2018, between the Registrant and James F. Maguire |   |   |   |   |   |   |   |   |   | * |
| 10.16+        |   | Executive Severance Agreement, dated as of January 13, 2012, between the Registrant and John W. Kosiba. |   | 8-K |   | 000-19672 |   | 10.1 |   | 4/4/2017 |   |   |
| 10.17+        |   | First Amendment to Executive Severance Agreement, effective as of July 31, 2017, between the Registrant and John W. Kosiba. |   | 10-Q |   | 000-19672 |   | 10.1 |   | 11/7/2017 |   |   |
| 10.18†  |   | Supply Contract, effective as of February 8, 2013, by and between the Registrant and Inox Wind Limited. |   | 8-K |   | 000-19672 |   | 10.1 |   | 2/14/2013 |   |   |
| 10.19†  |   | Supply Contract, effective as of June 2, 2014, by and between the Registrant and Inox Wind Limited. |   | 8-K |   | 000-19672 |   | 10.1 |   | 6/5/2014 |   |   |
| 10.20†  |   | Amendment No.1 to Supply Contract (dated June 2, 2014), by and between the Registrant and Inox Wind Limited, entered into by the Registrant on August 26, 2015. |   | 10-Q |   | 000-19672 |   | 10.1 |   | 11/3/2015 |   |   |
| 10.21†  |   | Amendment No.2 to Supply Contract (dated June 2, 2014), by and between the Registrant and Inox Wind Limited, entered into by the Registrant on December 14, 2015. |   | 10-Q |   | 000-19672 |   | 10.3 |   | 2/9/2016 |   |   |
| 10.22†  |   | Amendment No.3 to Supply Contract (dated June 3, 2014), by and between the Registrant and Inox Wind Limited, entered into on February 18, 2016. |   | 10-K |   | 000-19672 |   | 10.41 |   | 5/31/2016 |   |   |
| 10.23†  |   | Supply Contract, effective as of August 15, 2014, by and between the Registrant and Inox Wind Limited. |   | 10-Q |   | 000-19672 |   | 10.1 |   | 11/6/2014 |   |   |
| 10.24†  |   | Amendment No.1 to Supply Contract (effective as of August 15, 2014), by and between the Registrant and Inox Wind Limited, entered into by the Registrant on February 25, 2015. |   | 10-Q |   | 000-19672 |   | 10.2 |   | 11/3/2015 |   |   |

----

|                     |
|---------------------|
|                     |  |  |  |  |  |  |  |  |  |  |  |  |
|                |   |   |   | Incorporated by Reference |
| ExhibitNumber       |   | Exhibit Description |   | Form |   | File No. |   | Exhibit |   | FilingDate |   | Filed/FurnishedHerewith |
| 10.25†        |   | Amendment No.2 to Supply Contract (effective as of August 15, 2014), by and between the Registrant and Inox Wind Limited, entered into by the Registrant on August 26, 2015. |   | 10-Q |   | 000-19672 |   | 10.3 |   | 11/3/2015 |   |   |
| 10.26†        |   | Amendment No.3 to Supply Contract (effective as of August 15, 2014), by and between the Registrant and Inox Wind Limited, entered into on November 19, 2015. |   | 10-Q |   | 000-19672 |   | 10.4 |   | 2/9/2016 |   |   |
| 10.27†        |   | Amendment No.4 to Supply Contract (effective as of August 15, 2014), by and between the Registrant and Inox Wind Limited, entered into on February 18, 2016. |   | 10-K |   | 000-19672 |   | 10.46 |   | 5/31/2016 |   |   |
| 10.28†        |   | Supply Contract, dated December 16, 2015, by and between the Registrant and Inox Wind Limited. |   | 10-Q |   | 000-19672 |   | 10.1 |   | 2/9/2016 |   |   |
| 10.29†† |   | Amendment No. 1 to Supply Contract, entered into as of March 14, 2018 and effective as of November 8, 2017, by and between the Registrant and Inox Wind Limited. |   |   |   |   |   |   |   |   |   | * |
| 10.30†† |   | Amendment No. 2 to Supply Contract, entered into on May 21, 2018, by and between the Registrant and Inox Wind Limited. |   |   |   |   |   |   |   |   |   | * |
| 10.31†        |   | Technology License Agreement, dated December 16, 2015, by and among AMSC Austria GMBH, the Registrant and Inox Wind Limited. |   | 10-Q |   | 000-19672 |   | 10.2 |   | 2/9/2016 |   |   |
| 10.32†        |   | License and Sublicense Agreement, dated March 4, 2016, by and between the Registrant and BASF Corporation. |   | 10-K |   | 000-19672 |   | 10.49 |   | 5/31/2016 |   |   |
| 10.33†        |   | Disclosure Letter, dated March 4, 2016, by and between the Registrant and BASF Corporation. |   | 10-K |   | 000-19672 |   | 10.50 |   | 5/31/2016 |   |   |
| 10.34†        |   | Joint Development Agreement, dated March 4, 2016, by and between the Registrant and BASF Corporation. |   | 10-K |   | 000-19672 |   | 10.51 |   | 5/31/2016 |   |   |
| 10.35               |   | At Market Issuance Sales Agreement, by and between the Registrant and FBR Capital Markets & Co. |   | 8-K |   | 000-19672 |   | 10.1 |   | 1/27/2017 |   |   |
| 10.36               |   | Purchase and Sale Agreement, dated as of February 1, 2018, by and between ASC Devens LLC and 64 Jackson, LLC. |   | 8-K |   | 000-19672 |   | 10.1 |   | 2/1/2018 |   |   |
| 10.37               |   | Subordinated Secured Commercial Promissory Note of Jackson 64 MGI, LLC in favor of ASC Devens LLC dated March 28, 2018. |   | 8-K |   | 000-19672 |   | 10.1 |   | 4/3/2018 |   |   |
| 10.38               |   | Assignment of Purchase and Sale Agreement, dated as of March 26, 2018, by and among ASC Devens LLC, 64 Jackson, LLC and Jackson 64 MGI, LLC. |   | 8-K |   | 000-19672 |   | 10.2 |   | 4/3/2018 |   |   |
| 10.39               |   | Subordinated Second Mortgage of Jackson 64 MGI, LLC in favor of ASC Devens LLC effective March 28, 2018. |   | 8-K |   | 000-19672 |   | 10.3 |   | 4/3/2018 |   |   |

----

|               |
|---------------|
|               |  |  |  |  |  |  |  |  |  |  |  |  |
|          |   |   |   | Incorporated by Reference |
| ExhibitNumber |   | Exhibit Description |   | Form |   | File No. |   | Exhibit |   | FilingDate |   | Filed/FurnishedHerewith |
| 10.40         |   | Subordinated Second Assignment of Leases and Rents by Jackson 64 MGI, LLC to ASC Devens LLC dated March 28, 2018. |   | 8-K |   | 000-19672 |   | 10.4 |   | 4/3/2018 |   |   |
| 10.41         |   | Intercreditor, Subordination and Standstill Agreement by and among East Boston Savings Bank, ASC Devens LLC and Jackson 64 MGI, LLC dated March 28, 2018. |   | 8-K |   | 000-19672 |   | 10.5 |   | 4/3/2018 |   |   |
| 21.1          |   | Subsidiaries. |   |   |   |   |   |   |   |   |   | * |
| 23.1          |   | Consent of RSM US LLP |   |   |   |   |   |   |   |   |   | * |
| 31.1          |   | Chief Executive Officer - Certification pursuant to Rule 13a-14(a) or Rule 15d-14(a) of the Securities Exchange Act of 1934, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. |   |   |   |   |   |   |   |   |   | * |
| 31.2          |   | Chief Financial Officer - Certification pursuant to Rule 13a-14(a) or Rule 15d-14(a) of the Securities Exchange Act of 1934, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. |   |   |   |   |   |   |   |   |   | * |
| 31.3          |   | Chief Executive Officer - Certification pursuant to Rule 13a-14(a) or Rule 15d-14(a) of the Securities Exchange Act of 1934, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. |   |   |   |   |   |   |   |   |   | ** |
| 31.4          |   | Chief Financial Officer - Certification pursuant to Rule 13a-14(a) or Rule 15d-14(a) of the Securities Exchange Act of 1934, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. |   |   |   |   |   |   |   |   |   | ** |
| 32.1          |   | Chief Executive Officer - Certification pursuant to Rule13a-14(b) or Rule 15d-14(b) of the Securities Exchange Act of 1934 and 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. |   |   |   |   |   |   |   |   |   | *** |
| 32.2          |   | Chief Financial Officer - Certification pursuant to Rule 13a-14(b) or Rule 15d-14(b) of the Securities Exchange Act of 1934 and 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. |   |   |   |   |   |   |   |   |   | *** |
| 101.INS       |   | XBRL Instance Document.* |   |   |   |   |   |   |   |   |   |   |
| 101.SCH       |   | XBRL Taxonomy Extension Schema Document.* |   |   |   |   |   |   |   |   |   |   |
| 101.CAL       |   | XBRL Taxonomy Calculation Linkbase Document.* |   |   |   |   |   |   |   |   |   |   |
| 101.DEF       |   | XBRL Taxonomy Definition Linkbase Document.* |   |   |   |   |   |   |   |   |   |   |
| 101.LAB       |   | XBRL Taxonomy Label Linkbase Document.* |   |   |   |   |   |   |   |   |   |   |
| 101.PRE       |   | XBRL Taxonomy Presentation Linkbase Document.* |   |   |   |   |   |   |   |   |   |   |

----

|         |
|---------|
|         |  |
| † | Confidential treatment previously requested and granted with respect to certain portions, which portions were omitted and filed separately with the Commission. |

|                |
|----------------|
|                |  |
| †† | Confidential treatment has been requested with respect to certain portions of this exhibit, which portions have been filed separately with the Securities and Exchange Commission. |

|   |
|---|
|   |  |
| + | Management contract or compensatory plan or arrangement. |

|     |
|-----|
|     |  |
| *   | Previously filed with the Original Form 10-K. |
| **  | Filed herewith. |
| *** | Previously furnished with the Original Form 10-K. |

----

|                                          |
|------------------------------------------|
|                                          |  |  |
| AMERICAN SUPERCONDUCTOR CORPORATION |
|                                     |   |
|                                     | By: | /S/ JOHN W. KOSIBA, JR. |
|                                     |   | JOHN W. KOSIBA, JR. |
|                                     |   | Senior Vice President and Chief Financial Officer |
|                                     |
| Date: June 7, 2018                       |