It did not name the power transformer makers it had charged, but said the companies would be able to defend themselves in writing and at a hearing before the European Union decides on whether to fine them.
Germany's Siemens AG, France's Areva and Swiss engineering group ABB confirmed they had received the charges.
Power transformers are used to control the voltage in electrical circuits and are key components in transmission and distribution networks.
They are bought by major power generation and transmission companies so higher prices may raise costs and contribute to more expensive electricity prices for households and companies.
EU cartel fines can cost a company up to 10 percent of its global yearly revenue for each year it broke antitrust rules, often running into hundreds of millions of euros (dollars).
Officials raided several power transformer companies in France, Germany and Austria in February 2007.
Siemens AG spokesman Joern Roggenbuck confirmed that it was among those charged, but had no further comment.
The company said last year it had suspended three employees it suspected of colluding with rivals on the German market between 2001 and 2003. It said this happened before Siemens bought the Power Transmission and Distribution Group and VA Tech EBG units in 2005.
But Siemens said the behavior only became known as a result of the antitrust raids meaning it was not the first to blow the whistle on the cartel. Whistle-blowers usually win a complete amnesty from fines.
Areva said the charges related to behavior predating its January 2004 purchase of a power transmission and distribution business from Alstom SA.
ABB said in a statement that it had also been charged and that it had a zero tolerance policy for employees who broke the law or behaved unethically.