Sensex swung over 1,630 points intraday between its high and low as it suddenly fell after 3:00 pm before it closed nearly 1,100 points lower under 74,800 level. The index erased investor wealth worth ₹4,91,244 crore in about six hours as Power Grid, IndiGo, NTPC and M&M were the top losers. Meanwhile, Nifty closed nearly 400 points lower at 23,547.75.