Under the Securities Exchange Act of 1934
(Amendment No. )*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. o

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

* 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 disclosures provided in a prior cover page.

The information required on 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).

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Item 1.   Security and Issuer

This Statement on Schedule 13D (this “Statement”) relates to the common stock, $10.00 par value (the “Shares”) of SPX Corporation (the “Issuer” or the “Company”). The Issuer’s principal executive offices are located at 13515 Ballantyne Corporate Place, Charlotte, NC 28277.

Item 2.   Identity and Background

This Statement is being filed by and on behalf of Relational Investors Mid-Cap Fund I, L.P. (“MC I”), Relational Investors Mid-Cap Fund II, L.P. (“MC II”), Relational Fund Partners, L.P. (“RFP”), Relational Coast Partners, L.P. (“RCP”), Relational Investors IX, L.P. (“RI IX”), Relational Investors XV, L.P. (“RI XV”), Relational Investors XX, L.P. (“RI XX”) and Relational Investors XXIII, L.P. (“RI XXIII”), collectively, the “Relational LPs.”  Each of the Relational LPs is a Delaware limited partnership.  The principal business of each, is investing in securities.

This Statement is also being filed by Relational Investors, LLC (“RILLC”), a Delaware limited liability company.  The principal business of RILLC is being the sole general partner or sole managing member of the general partner of certain investment partnerships, including the Relational LPs and the investment adviser of certain client managed accounts, the “Managed Accounts”.  The Relational LPs and the Managed Accounts are the beneficial owners of the securities covered by this Statement.  Pursuant to the Limited Partnership Agreement of each of the Relational LPs, and the investment management agreement of the Managed Accounts, RILLC has sole investment discretion and voting authority with respect to the securities covered by this Statement.

This Statement is also being filed by Ralph V. Whitworth and David H. Batchelder.  Messrs. Whitworth and Batchelder are the Principals of RILLC, in which capacity they share voting control and dispositive power over certain securities covered by this Statement.  As such, Messrs. Whitworth and Batchelder may be deemed to have indirect beneficial ownership of such securities, but, each of Mr. Whitworth and Mr. Batchelder disclaim beneficial ownership of the Shares except to the extent of his pecuniary interest therein.  The present principal occupation of each of Messrs. Whitworth and Batchelder is serving as Principals of RILLC (Messrs. Whitworth and Batchelder, together with Relational LPs and RILLC, hereinafter, the “Reporting Persons”).

During the last five years, none of the Reporting Persons has been (i) convicted in a criminal proceeding (excluding traffic violations and similar misdemeanors) or (ii) a party to a civil proceeding of a judicial or administrative body of competent jurisdiction, and as a result of such proceeding, was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

The business address of each of the Reporting Persons is 12400 High Bluff Drive, Suite 600, San Diego, CA 92130.

Messrs. Whitworth and Batchelder are each citizens of the United States.

Item 3.   Source and Amount of Funds or Other Consideration

RILLC and the Managed Accounts purchased an aggregate of 964,578 Shares for a total consideration (including brokerage commissions) of $73.6 million derived from capital of RILLC and the Managed Accounts.

The Relational LPs purchased an aggregate of 3,150,204 Shares for total consideration (including brokerage commissions) of $233.2 million derived from the capital of the Relational LPs and margin borrowings from Credit Suisse Securities (USA) LLC (“CSSU”) for RFP, RCP, RI XX and RI XXIII.

Interest on the margin debt balance of the margin accounts described above is charged at the then Federal Funds Rate plus 50 basis points.  CSSU has a lien on the Shares held by RFP, RCP, RI XX and RI XXIII to secure repayment of the margin borrowings described above.

Item 4.   Purpose of Transaction

The Reporting Persons acquired the Shares covered by this Statement because, in their opinion, such Shares are significantly undervalued due to the factors described below.

Despite the Company’s attractive business mix, total shareholder returns and profitability have lagged peers’ due primarily to excessive prices paid for acquisitions.  This growth-at-any-cost strategy destroys shareholder value by overly emphasizing revenue growth over investment returns.  The Reporting Persons believe that major improvements in a number of critical business processes will unlock significant intrinsic value for the Company’s shareholders.  These essential improvements include: increasing operating profit margins to levels achieved by comparable peer businesses, accelerating divestment of non-core underperforming assets around the Company’s Flow business, establishing rigorous capital allocation disciplines and processes that properly balance growth and investment returns, and properly aligning executive compensation and shareholder value creation.

The Reporting persons believe that the significant drop in the company’s stock price that occurred in December of 2012 and the subsequent stock price volatility reflected the market’s lack of confidence in the board and management’s ability to properly discipline capital allocation and assess acquisition opportunities.  The Reporting Persons believe the Company should focus on improving its core assets and avoid future acquisitions unless they convincingly offer risk-adjusted returns well in excess of the Company’s weighted average cost of capital and compare favorably to share repurchases.  Furthermore, executive incentives should be modified to drive and reinforce this capital allocation framework.

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If the Company fails to achieve operating margins consistent with peers and gain the confidence of investors, leading to a substantial increase in valuation, we believe the Company should explore strategic alternatives for better achieving the long-term intrinsic value of the assets.

The Reporting Persons intend to closely monitor the Company’s progress in each of these areas and may modify their plans accordingly.

The Reporting Persons may exercise any and all of their respective rights as shareholders of the Company in a manner consistent with their equity interests.  The Reporting Persons and their representatives and advisers intend to discuss the Company and its performance with members of the Company’s board and management.  In addition, the Reporting Persons may communicate with other shareholders, industry participants and other interested parties concerning the Company.  Although the Reporting Persons do not have any current plans, other than the monitoring and communication program outlined above, the Reporting Persons may in the future decide to seek representation on the Company’s board of directors.  Among other factors, the Reporting Persons will consider the Board’s oversight of the execution of operational improvements and capital allocation strategies for maximizing shareholder value as major factors in its decision of whether or not to nominate independent director candidates.

The Reporting Persons may from time to time (i) acquire additional Shares (subject to availability at prices deemed favorable) in the open market, in privately negotiated transactions or otherwise, or (ii) dispose of Shares at prices deemed favorable in the open market, in privately negotiated transactions or otherwise.  The Reporting Persons may formulate plans or proposals for, and may from time to time explore, or make proposals relating to, transactions or actions which relate to or would result in any of the matters specified in clauses (a) through (j) of Item 4 of Schedule 13D.

Item 5.   Interest in Securities of the Issuer

(a)           As of the date of this Statement, the Reporting Persons beneficially owned in the aggregate 4,114,782 Shares, constituting 8.76% of the outstanding Shares.  The percentage of Shares owned is based upon 46,985,608 Shares outstanding on February 15, 2013, as set forth in the Issuer’s Form 10-K for the year ended December 31, 2012.  The Reporting Persons may be deemed to have direct beneficial ownership of the Shares as follows:

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RILLC, individually and in its capacity as an investment adviser, may be deemed to possess direct beneficial ownership of the 964,578 Shares that are owned by it and the Managed Accounts.  Additionally, RILLC, as the sole general partner, or sole managing member of the general partner, of each of the Relational LPs may be deemed to beneficially own (as that term is defined in Rule 13d-3 under the Securities Exchange Act of 1934, as amended) the 3,150,204 Shares beneficially owned by the Relational LPs because the limited partnership agreements of the Relational LPs specify that RILLC has sole investment discretion and voting authority with respect to those Shares.

Each of Messrs. Whitworth and Batchelder, as Principals of RILLC, may be deemed to share indirect beneficial ownership of the Shares which RILLC may beneficially own.  Each of Messrs. Whitworth and Batchelder disclaims beneficial ownership of such Shares for all other purposes.

To the best of the knowledge of each of the Reporting Persons, other than as set forth above, none of the persons named in Item 2 is the beneficial owner of any Shares.

(b)           See item (a) above.

(c)           Except as set forth in Exhibit A to this Statement, none of the Reporting Persons has effected any transactions in the Shares during the past sixty days.

(d)           No other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Shares covered by this Statement, except that dividends from, and proceeds from the sale of, the Shares held by accounts managed by RILLC may be delivered to such accounts.

(e)           Not applicable.

Item 6.  Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer

Except for the joint filing agreement between and among the Reporting Persons attached hereto as Exhibit B, and except for the investment discretion and voting authority described in Item 2 of this Statement and in the respective partnership agreements and investment management agreements of the Relational LPs and Managed Accounts which each contain provisions whereby RILLC may, after certain adjustments, receive a percentage of realized or unrealized profits, if any, derived from that partnership’s or managed account’s investments, to the best of the knowledge of the Reporting Persons, there are no contracts, arrangements, understandings or relationships (legal or otherwise) among the Reporting Persons or between the Reporting Persons and any other person with respect to any securities of the Issuer, including but not limited to transfer or voting of any of the securities, finder’s fees, joint ventures, loan or option arrangements, puts or calls, guarantees of profits, division of profits or loss, or the giving or withholding of proxies.

Item 7.  Material to Be Filed as Exhibits

The following Exhibits are filed herewith:

Exhibit A – Information concerning transactions in the Shares effected by the Reporting Persons in the last 60 days.

Exhibit B – Joint Filing Agreement.

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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.

Dated:  February 25, 2013

RELATIONAL INVESTORS MID-CAP FUND I, L.P.
RELATIONAL INVESTORS MID-CAP FUND II, L.P.
RELATIONAL FUND PARTNERS, L.P.
RELATIONAL COAST PARTNERS, L.P.
RELATIONAL INVESTORS IX, L.P.
RELATIONAL INVESTORS XV, L.P.
RELATIONAL INVESTORS XX, L.P.
RELATIONAL INVESTORS XXIII, L.P.

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Exhibit A

Transactions by Reporting Persons in the last 60 days.