BEIJING, Aug 11 (Reuters) - The Shanghai Futures Exchange on Friday urged investors to trade "rationally" and keep the market stable, as it moved to limit intraday rebar positions and raise transaction fees.

In a series of statements designed to calm volatile trading, one of China's major commodity derivatives markets said it would limit intraday positions for non-member firms and clients on rebar futures contracts for delivery in October 2017 and January 2018 to 8,000 lots from Aug. 15.

Hedging transactions are not affected by the limits.

The exchange will also raise intraday transaction fees on those contracts to 0.05 percent of the total value from 0.01 percent previously.

Sources told Reuters earlier on Friday that the exchange had informed members it may raise margins on steel rebar futures contracts if turnover is too high.

(Reporting by Tom Daly; Editing by Josephine Mason and Tom Hogue)