Which type of single-phase alternating-current motor has the highest efficiency?

Why do electric utility companies transmit power at high voltages?

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An outdoor parking area has 25 light poles. Each pole has a 420 Watt (ballast included) high-pressure sodium (HPS) luminaire. The parking area lights are illuminated 4,500 hours per year and the electricity cost is $0.08/kWh. What is the annual energy cost reduction if each luminaire is replaced with a 220-Watt (driver included) LED luminaire?

A 55-kW motor at full load is used to drive a pump that generates 50 meters of head while pumping water at a rate of 5,000 liters per minute. Calculate the pump efficiency.

How much fuel is required to heat 50 kg water from 20°C water to 200°C saturated steam? Assume the boiler is 80% efficient (based on the higher-heating value of the fuel).

What is a common cause of poor power quality?

A gas-fired boiler is operating with 31.9% excess air. A feedwater economizer is used to reduce the stack temperature rise from 310°C to 160°C. Using the natural gas combustion efficiency tables in your workbook, find the energy savings from the economizer as a percentage of historical fuel consumption.

A three phase, 380.volt system has the following voltage measurements:

Va = 375$ volts

Vb = 380$ volts

Vc = 391$ volts

Calculate the percent voltage imbalance.

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A compressed-air distribution system has one section that frequently has low pressure when demand for compressed air is high. How can you resolve the problem without increasing energy consumption?

An energy project implemented today saves $10,000 per year for the next 20 years. Using the 5% interest table, determine the total value of savings at the end of the 20th year?