Dynalectric, a McLean electrical contracting firm that pleaded guilty to bid rigging charges in Kentucky last month, was fined $1 million by a federal judge in Louisville yesterday.

G. Walther Ewalt, the firm's former president and the former chief operating officer of Dynalectric's parent, DynCorp, received a two-year jail term with all but six months suspended. Ewalt had also pleaded guilty in the case last month.

Dynalectric had been charged with conspiring with a competitor, Fishbach and Moore Inc., to rig bids on an electrical contract awarded by a Kentucky rural electric cooperative in 1982.

The fine against Dynalectric yesterday follows a fine of $1.5 million imposed on the firm last April after its conviction in a separate bid rigging case in Atlanta. A DynCorp spokesman said yesterday that the combined fines would be covered by a $3.51 million reserve the firm set up to cover potential fines in the two cases last year. The Justice Department had asked for a fine of $6 million in the Kentucky case.

Ewalt received an identical jail sentence -- two years with all but six months suspended -- in the Atlanta case. Dynalectric and Ewalt are appealing their convictions in Atlanta. The sentence Ewalt received yesterday will be added to any jail time he serves in the Atlanta case.

In a separate development, DME Holdings Inc., a DynCorp management group headed by DynCorp President Dan R. Bannister, is expected to make a counterbid for the company today, sources close to DynCorp said yesterday. Last month, company chairman Jorge E. Carnicero appeared to have won a final victory in the three-month tussle for control of the company -- one of Washington's largest professional and technical services firms -- by making an offer worth about $226 million. That bid has been tentatively accepted by the board.

Carnicero made a $270 million offer for the company in October, but it was rejected by the board. Subsequently, the stock market collapse on Oct. 19 hammered DynCorp's stock price and the board accepted a bid from the Bannister group of $248 million. That offer was sweetened to as much as $270 million, but fell apart when DynCorp's board failed to make a decision on the offer before a bank financing commitment to complete the deal expired. That allowed Carnicero to reenter the bidding.