Motor Drive System Homework - University of Dayton



Energy Efficient ManufacturingMotor Drive System HomeworkFor all problems assume the average cost of electricity is $0.10 /kWh (including demand cost).The measured current, voltage and power factor of a premium-efficient, three-phase, 125-hp air compressor motor are shown in the table below. Assume the motor is 95.3% efficient at all loads.Loaded UnloadedCurrent (Amps) 12763Voltage (Volts)476476Power Factor (kW/kVA).92.81Calculate the power draw of the motor in kW when loaded and unloaded. Calculate the power output of the motor in hp when loaded and unloaded.Calculate the fraction loaded of the motor when loaded and unloaded.If the service factor is 1.05, is the motor in danger of premature failure?Calculate the annual electricity cost if the motor cycles between running loaded for 40 seconds then unloaded for 60 seconds, and operates 5,000 hours per year. A 93%-efficient 100-hp motor runs 6,000 hours per year and produces power for a fan that requires 75 hp of shaft work. Calculate the annual electricity cost of the motor if the pulleys use 92%-efficient standard V-beltsCalculate the annual electricity cost of the motor if the pulleys use 96%-efficient notched V-belts. Calculate the annual electricity cost savings from switching from standard to notched V-belts.Calculate the simple paybacks of replacing a failed 75%-loaded, 15-hp, standard-efficiency motor with an energy-efficient motor rather than rewinding it, if the motor runs 2,000, 5,000 and 8,000 hours per year.A 20-hp motor runs 5,000 hours per year, produces 4 hp of shaft work, and operates at 50% efficiency with a power factor of 0.60 kW/kVA. Calculate the power draw (kW), reactive power (kVAr) and annual energy consumption (kWh/yr) of the motor. If motor were replaced with an energy-efficient 5-hp motor operating at 90% efficiency with a power factor of 85%, calculate the power draw (kW), reactive power (kVAr) and annual energy consumption (kWh/yr) of the “right-sized” motor. Calculate the annual electricity cost savings from rightsizing the motor. Using Motor Master+ data (but not the software!) for the cost of the new motor, calculate the simple payback for right-sizing the oversized motor.If the power factor charge is $0.60 /kVAr-mo, calculate the annual power factor cost savings from rightsizing the motor. (Do not include this cost savings in part C or D above.) ................
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