BME 410 Electrical Power Machinery Homework Set #1 - Power Question #1 A large fan requires a torque of 260 ft-lbs to operate at 1740 RPM. What is the minimum horsepower rating of the motor to drive the fan? If the motor is 90% efficient what is minimum input power required by the motor in kW? Question #2 A garage lift is designed to lift a 10,000lb truck to a height of 6ft in 15 seconds. Assuming that the hydraulic system is 30% efficient what is the minimum horsepower rating of the motor powering the hydraulic system? If that motor is 85% efficient what is minimum input power required by the motor in kW? Question #3 An electrical utility delivers 6.25E10 kWh of power to its customers in a year. What is the average power required during the year? If the powerplants supplying the utility have an average efficiency of 45% how much energy (in quads) does the power plants use in a year? Assuming that the power plants burn natural gas how many cubic feet of natural gas will be required to generate that much power? Question #4 A large university campus has a peak power demand of 20Mw and purchases 6E6 kWh of electrical energy per month. The utility charges the university $7.50/kW of peak demand plus 3.4¢/kWh. Calculate the monthly and yearly power bills. Question #5 A standby generator powered by and internal combustion engine has a rated capacity of 100kW. Assuming that the generator is 90% efficient how much horsepower must the engine deliver to the generator at full load? Assuming that the thermal efficiency of the engine is 35% how much diesel fuel will the engine consume in one hour at full load?
