CPU PART 3 SOLVED PROBLEMS

An electric pump has total resistance of 9.5 ohms. If its power source is from a 220-volt outlet, what should be the amperage of its safety fuse? Assume 27 % surge current

• 45 amp

• 40 amp

• 30 amp

• NOTA

Answer explanation

I = 1.27V/R = 1.27(220V)/9.5Ω

= 29.41Amp (Use 30Amp)

What is the power generated by a micro-hydropower plant having a gross head of 80 meters and reliable discharge of 50 liters/second. Assume typical efficiency

• 23.5 kw

• 28.5 kw

• 38.5 kw

• NOTA

Answer explanation

P = 9.8QHE = 9.8 ( 0.05m3/s )(80m)(0.6) = 23.52. kW

Give the estimated mechanical power output of a windmill having a rotor diameter of 8 meters if wind velocity is 3 m/s

• 0.136 kw

• 0.246 kw

• 0.316 kw

• NOTA

Answer explanation

What is the electrical energy consumption of a 10-kw coconut oil expeller plugged in a 220-volt source if it requires 3 hours to expel oil from 1,000 kg of grated copra?

• 0.03 kwh/kg

• 0.05 kwh/kg

• 0.07 kwh/kg

• NOTA

Answer explanation

What is the peak solar power generation per charging channel of a solar battery charging station equipped with 12 units of 75 watt-peak 12-volt solar module? The system is divided into 3 charging channels, each channel has 4 modules connected in parallel. Assume 80% overall efficiency

• 2.4 kWp

• 240 Wp

• 260 Wp

• NOTA

Answer explanation

An industrial heater has 8 pieces heating plates of 6 ohms each. Plates are arranged in series. If the heater power source is from a 220-volt outlet, how much current will flow?

• 3.5 amp

• 4.6 amp

• 5.2 amp

• NOTA

Answer explanation

How much should be budgeted annually for the electrical consumption of a 20-kw coconut oil expeller drawing 92 amperes current and having an electrical consumption of 0.04 kwh/kg copra? It expels 250 kg of copra per hour and operates 16 h/day at 264 days/year. Electricity costs PHP5/kwh. Use 10% cost safety factor

• PHP132,560

• PHP 232,320

• PHP100,160

• NOTA

Answer explanation

What is the peak amperage of a solar battery charging station equipped with 16 units of 75 watt-peak 4.16-ampere solar module? The system is divided into 4 charging channels, each channel has 4 modules connected in parallel

• 32.2 A

• 25.4 A

• 16.6 A

• NOTA

Answer explanation

What is the system voltage of a solar pumping system equipped with 2 units of 75 watt-peak solar modules? Each solar module has 4.16 amperes maximum, open circuit voltage of 21 volts maximum and nominal voltage of 12 volts. Modules are connected in series

• 48 Volts

• 36 Volts

• 24 Volts

• NOTA

Answer explanation

Estimate the hydraulic power output of a multi-bladed windmill when windspeed is 3 m/s. It has 0.3 rotor power coefficient, 90% transmission efficiency, 90% pump volumetric efficiency and 6 meters rotor diameter. Air density is 1.2 kg/m3

• 38.8 watts

• 26.4 watts

• 65.7 watts

• NOTA

Answer explanation