UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934

                              (Amendment No. ____)*

                       American Superconductor Corporation
                                (Name of Issuer)

                                  Common Stock
                         (Title of Class of Securities)

                                    030111108
                                 (CUSIP Number)

                                December 31, 2006
             (Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

[X]  Rule 13d-1(b)

[ ]  Rule 13d-1(c)

[ ]  Rule 13d-1(d)

*    The remainder of this cover page shall be filled out for a reporting
     person's initial filing on this form with respect to the subject class of
     securities, and for any subsequent amendment containing information which
     would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).



                                  SCHEDULE 13G

CUSIP No. 030111108

--------------------------------------------------------------------------------
1.   Names of Reporting Persons. I.R.S. Identification Nos. of above persons
     (entities only).

     AMVESCAP PLC
     PowerShares Capital Managements LLC
     Stein Roe Investment Counsel, Inc.
--------------------------------------------------------------------------------
2.   Check the Appropriate Box if a Member of a Group (see Instructions)

     (a)  [ ]
     (b)  [ ]
--------------------------------------------------------------------------------
3.   SEC Use Only

--------------------------------------------------------------------------------
4.   Citizenship or Place of Organization

     AMVESCAP PLC: England
     PowerShares Capital Management LLC: United States
     Stein Roe Investment Counsel, Inc. - United States
--------------------------------------------------------------------------------
                     5.   Sole Voting Power 2,108,837: Such shares are held by
                          the following entities in the respective amounts
                          listed:

                          PowerShares Capital Management LLC   2,107,337
                          Stein Roe Investment Counsel, Inc.       1,500
                     -----------------------------------------------------------
                     6.   Shared Voting Power
 Number of Shares
Beneficially Owned        -0-
 by Each Reporting   -----------------------------------------------------------
    Person With      7.   Sole Dispositive Power 2,108,837: Such shares are held
                          by the following entities in the respective amounts
                          listed:

                          PowerShares Capital Management LLC   2,107,337
                          Stein Roe Investment Counsel, Inc.       1,500
                     -----------------------------------------------------------
                     8.   Shared Dispositive Power

                          -0-
--------------------------------------------------------------------------------
9.   Aggregate Amount Beneficially Owned by Each Reporting Person

     2,108,837
--------------------------------------------------------------------------------
10.  Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See
     Instructions)

     N/A
--------------------------------------------------------------------------------
11.  Percent of Class Represented by Amount in Row (9)

     6.31%
--------------------------------------------------------------------------------
12.  Type of Reporting Person (See Instructions)

     IA, HC. See Items 2 and 3 of this statement.
--------------------------------------------------------------------------------



                                  SCHEDULE 13G

Item 1(a) Name of Issuer:

          American Superconductor Corporation

Item 1(b) Address of Issuer's Principal Executive Offices:

          Two Technology Drive
          Westborough, MA 01581

Item 2(a) Name of Person Filing:

          AMVESCAP PLC

          In accordance with Securities and Exchange Commission Release No.
          34-39538 (January 12, 1998), this statement on Schedule 13G or
          amendment thereto is being filed by AMVESCAP PLC ("AMVESCAP"), a U.K.
          entity, on behalf of itself and its subsidiaries listed in Item 4 of
          the cover of this statement. AMVESCAP through such subsidiaries
          provides investment management services to institutional and
          individual investors worldwide.

          Executive officers and directors of AMVESCAP or its subsidiaries may
          beneficially own shares of the securities of the issuer to which this
          statement relates (the "Shares"), and such Shares are not reported in
          this statement. AMVESCAP and its subsidiaries disclaim beneficial
          ownership of Shares beneficially owned by any of their executive
          officers and directors. Each of AMVESCAP's direct and indirect
          subsidiaries also disclaim beneficial ownership of Shares beneficially
          owned by AMVESCAP and any other subsidiary.

Item 2(b) Address of Principal Business Office:

          30 Finsbury Square
          London EC2A 1AG
          England

Item 2(c) Citizenship:

          See the response to Item 2(a) of this statement.

Item 2(d) Title of Class of Securities:

          Common Stock, $.01 par value per share

Item 2(e) CUSIP Number:

          030111108

Item 3    If this statement is filed pursuant to ss240.13d-1(b) or 240.13d-2(b)
          or (c), check whether the person filing is a:

          (e)  [X]  An investment adviser in accordance with section
                    240.13d-1(b)(1)(ii)(E)

          (g)  [X]  A parent holding company or control person in accordance
                    with section 240.13d-1(b)(1)(ii)(G)

          As noted in Item 2 above, AMVESCAP is making this filing on behalf of
          its subsidiaries listed herein. Each of these entities is either an
          investment adviser registered with the United States Securities and
          Exchange Commission under Section 203 of the Investment Advisers Act
          of 1940, as amended, or under similar laws of other jurisdictions.
          AMVESCAP is a holding company.



Item 4    Ownership:

          Please see responses to Items 5-8 on the cover of this statement,
          which are incorporated herein by reference.

Item 5    Ownership of Five Percent or Less of a Class:

          If this statement is being filed to report the fact that as of the
          date hereof the reporting person has ceased to be the beneficial owner
          of more than five percent of the class of securities, check the
          following [ ]

Item 6    Ownership of More than Five Percent on Behalf of Another Person:

          N/A

Item 7    Identification and Classification of the Subsidiary Which Acquired the
          Security Being reported on By the Parent Holding Company:

          Please see Item 3 of this statement, which is incorporated herein by
          reference.

Item 8    Identification and Classification of Members of the Group:

          N/A

Item 9    Notice of Dissolution of a Group:

          N/A

Item 10   Certification:

          By signing below I certify that, to the best of my knowledge and
          belief, the securities referred to above were acquired and are held in
          the ordinary course of business and were not acquired and are not held
          for the purpose of or with the effect of changing or influencing the
          control of the issuer of the securities and were not acquired and are
          not held in connection with or as a participant in any transaction
          having that purpose or effect.

          Signature:

          After reasonable inquiry and to the best of my knowledge and belief, I
          certify that the information set forth in this statement is true,
          complete and correct.

                                        02/14/2007
                                        Date

                                        AMVESCAP PLC


                                        By: /s/ Lisa Brinkley
                                            ------------------------------------
                                            Lisa Brinkley
                                            Chief Compliance Officer



                                  Exhibit Index

Exhibit A   Joint Filing Agreement