7.5hp motor how many kwh per houer?

You need to learn what the words mean. Power is the rate of doing work. A horsepower is called that because a strong horse can lift 550 pounds at one foot per second. 550 foot-pounds per second happens to equal 746 watts.

If work is done for one hour that is a horsepower-hour or a watt-hour or a kilowatt-hour.

7.5 hp x 746 w/hp x kw/1000w = 5.595 kw