As per this support page, you will not be able to place more than 2000 NRML/MIS/CNC/AMO orders per day.
Also, there is a maximum quantity limit of 1,00,000 shares per order (Refer to this support page).
Other than that, there is also an Order value limit of 2 Crore (Check this support page)
According to the above rules, you should theoretically be able to place a single order of maximum 13,434 shares of HDFC Bank (at the closing price of Rs.1488.7, the order value would be 13,434 * 1,488.7 = 1,99,99,195.8) and repeat that order 2,000 times. Which would mean, you will theoretically be able to purchase a total of 2,68,68,000 shares ( 2,000 * 13,434 ) in a day at maximum.
Also, in genuine cases, the 2000 orders per/day limit can be relaxed further (Refer to this thread)