UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported):

December 19, 2014

American Superconductor Corporation

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code (978) 842-3000

Not Applicable

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

On December 19, 2014, American Superconductor Corporation (the “Company”), ASC Devens, LLC, a wholly-owned subsidiary of the Company (“Devens”) and Superconductivity, Inc., a wholly-owned subsidiary of the Company (“Superconductivity,” together with the Company and Devens, each, a “Loan Party” and collectively, the “Loan Parties”) entered into a Second Amendment to Loan and Security Agreement (the “Second Amendment”) with Hercules Technology Growth Capital, Inc. (the “Lender”). The Second Amendment amended the Loan and Security Agreement dated as of June 5, 2012, as amended by the First Amendment to Loan and Security Agreement dated as of November 15, 2013 (the “Loan Agreement,” together with the Second Amendment, the “Amended Loan Agreement”), that the Loan Parties previously entered into with the Lender.

The terms of the Second Amendment, among other things:

The Lender and Devens also amended that certain Mortgage and Security Agreement dated July 31, 2012, as amended on November 15, 2013, with respect to the property Devens has rights to located at 64 Jackson Road, Devens, Massachusetts 01434-4020 (the “Mortgage”) so that it continues to secure the full amounts outstanding under the Amended Loan Agreement.

In connection with the Amended Loan Agreement, the Company entered into an Amended and Restated Warrant Agreement (the “New Warrant”) to purchase 588,235 shares the Company’s Common Stock, par value $0.01 per share, at an exercise price of $1.10, subject to price-based anti-dilution and other adjustments as set forth in the New Warrant. The New Warrant amended and restated the Warrant Agreement to purchase 256,410 shares of Common Stock, dated November 15, 2013 (the “Original Warrant”), and replaces and supersedes all other warrant agreements with the Lender, including the Warrant Agreement to purchase 139,276 shares of Common Stock, dated June 5, 2012, as amended on November 15, 2013. The New Warrant is immediately exercisable, subject to certain conditions, and expires on June 30, 2020. The Original Warrant, as amended and restated by the New Warrant, was issued in reliance on the exemption from registration provided by Section 4(2) of the Securities Act of 1933.

In connection with the closing of the Second Amendment, the Company also paid the Lender a facility charge of $15,000. Furthermore, on the earliest to occur of (i) the Initial Maturity Date, (ii) the Extended Maturity Date, (iii) the date that the Company prepays the New Term Loan, or (iv) the date that the New Term Loan becomes due and payable, the Company agreed to pay the Lender an end of term charge of $75,000.

The foregoing descriptions of the New Warrant and Second Amendment are summaries, and are qualified in its entirety by reference to the such documents, which are filed herewith as Exhibit 4.1 and Exhibit 10.1, respectively, and are incorporated herein by reference.

The information set forth in Item 1.01 is incorporated in this Item 2.03 by reference.

The information set forth in Item 1.01 in connection with the New Warrant is incorporated in this Item 3.02 by reference.

(d) Exhibits:

A list of exhibits is set forth in the Exhibit Index which immediately precedes such Exhibits and is incorporated herein by reference.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

EXHIBIT INDEX