Electrical Engineering Specifications - Assignment Example

ELECTRICAL ENGINEERING SPECIFICATIONS Name Institution Date Conceptual calculations, drawings, and justification to support the design of power supply to the pump When determining the size of a pump to be put into any use, it is important to carry out calculations that will justify the viability of the pump to execute its intended purpose with regard to the amount of the available power, for instance, electric motor of a specific rating (Casazza & Delea, 2003) and (Ward, 2007). Before setting up the pump, detailed working design drawings are prepared. The following information should also be determined in the field; The head available for the pump, The depth of the well to be bored, The topography of where the well is located. The water table with regards to the aquifer position and depth. Losses should also be determined as follows in order to approximate the efficiency of the pump. The mount of available horsepower requirements for pumping water is determined as follows; …………………………………………….. (i) Where, Pwhp= water horsepower (hp) Q = volumetric water flow in m3 Sg= specific gravity of water Impeller pumps are preferred over other pumps for water distribution. Depending on the temperature of water, different volumetric flow values will yield different amount of power as shown below; Reasons for poor pump performance A number of reasons can affect the performance of the pump. Some of them include: Low energy efficiency Worn drivers and wear rings Cavitations due to low suction Other unfavorable operating conditions Criteria for choosing power source The criteria used depends on the advantages and disadvantages of the available options, for instance, Power source Advantages Disadvantages Electric Motor High reliability Low maintenance High efficiency Less government regulations Simple to operate Require professional repair Not mobile of flexible Possibility of brownouts and blackouts Safety issues at high voltage Require standby charges Internal Combustion Engine Can be maintained by the owner Mobile and flexible cheaper Low reliability More maintenance More government regulations Low efficiency Price fluctuations It is also important to consider renewable energy sources such as solar and wind because they are comparatively cheaper and clean to use with minimal environmental issues. Figure 1 illustration of a water pump Figure 1 shows an illustration of a water pump Figure 2operating fundamentals Figure 2 shows the operating fundamentals of water pump Conceptual calculations and diagrams to determine power efficiency, power output and the pump capacity for translating water up steep terrain. According to Mays (1999). There are several conceptual calculations involved in the determination of the power efficiency and pump behavior in terms of its capacity to pump water uphill depending on the head and water table. These calculations also take into consideration the losses experienced during water pumping process and also in the pumping power source. Performance characteristics of the pump can be graphically determined in order to select the appropriate water pump (Mays, 2001). By determining the flow and the head at different flow values, total head is measured against different values of flow measurements. Calculation of losses and pump efficiency Much loss occur during conversion from electrical to mechanical energy through the pumping system and fluid transmission (Qasim, Motley & Zhu, 2000). Internal pump losses Load losses: these result due to fluid turbulence and viscosity. Leakage losses: these result due to the gap between fixed and moving parts. Internal friction losses: these occur due to viscous friction caused by inactive surfaces of the centrifugal pump impeller. External losses External leakage: these occur due to the crossing of the shaft to the machine housing. External frictional losses: these result from the mechanical friction that occurs in the packing of the pump bearing or shaft. Calculation of the Overall efficiency of the operating pump Where P s= output total power gauge = Pm = absorbed mechanical power in HP by the pump Q = rate of flow (m3/s) density of pumped water in kg/m3 acceleration as a result of gravity(m/s2) total pumping Head (mwc) Owing to the difficulty in separately determining the mechanical power and consequently the pump efficiency, evaluation of the electromechanical efficiency of the pump-motor assembly is recommended. Ph= gauge power (KW) Ht = total pumping head (mwc) Q = flow rate (m3/s) ϒ = specific weight of water (Kg/m3) = 1 g= acceleration due to gravity (m/s2) = 9.81 Flow rate Q is obtained in the field; ϒ and g are constant depending on the temperature of the place. Determination of the total pumping head Ht Where the suction pressure is to be measured, the following equation will be appropriate Where Ht = total pumping head (mwc) Pd= measured discharge pressure (kg/cm2) Ps = suction pressure that is measured in kg/cm2 Where the suction pressure was not measured as a result of deep wells, the following equation is recommended, Where: Ht = total pumping head (mwc) Pd= measured discharge pressure (kg/cm2) Ns = suction level determined from reference level Nr (m) Dr-m = distance between the reference level end the centre of the gauge (m) hv = velocity head (m) hfs=friction losses in discharge pipes and suction (m) Velocity Head hv This parameter depends on the pipe diameter Discharge cross-sectional area m3 Where: A = pipe cross-sectional area(m2) D = pipe diameter (m) ∏ = 22/7 From these equations, fluid velocity (v) = Q/A m/s Therefore, Frictional losses in suction and Discharge pipes hfs Where; f= friction factor(-) L= pipe length(m) D= pipe diameter (m) V= fluid velocity(m/s) g= acceleration as a result of gravity(m/s2) f is determined from the following Colebrook White equation Re = Reynolds Number = Where, =fluid velocity(m/s) D = pipe diameter(m) Fluid density Kg/m3 = fluid dynamic viscosity Determination of electromechanical efficiency Where, =electromechanical efficiency (-) Ph= gauge power (KW) Pe=motor electric power input (KW) Pump Efficiency determination The efficiency of the pump is thus calculated as follows, Where, =motor efficiency Circuits and diagrams for the float valve and water pump connection with power supply Float valve connection diagrams and circuit diagrams are illustrated as shown below. Figure 3 float valve switch Figure 3 above shows float switch relay for closing and opening the pump. Figure 4 float switch Figure 4 above shows a float switch installed with a bilge circuit breaker to protect the bilge pumps connected to isolation diodes and LED indicators Figure 5 circuit diagram for fluid level switch Figure 5 illustrates circuit control diagram for controlling the fluid level switch. This helps in determining the fluctuations in the water levels in the well. Figure 6 float switch control circuit Figure 6 above shows a schematic diagram of the float switch control circuit with DC power supply connected to the water pump. References Top of Form CASAZZA, J., & DELEA, F. (2003). Understanding electric power systems: an overview of the technology and the marketplace. [Piscataway, NJ], IEEE Press. Top of Form MAYS, L. W. (1999). Hydraulic design handbook. New York, McGraw-Hill. MAYS, L. W. (2001). Water resources engineering. New York,Wiley. QASIM, S. , MOTLEY, E., & ZHU, G. (2000). Water works engineering: planning, design, and operation. Upper Saddle River, NJ, Prentice Hall PTR.Bottom of Form Bottom of Form WARD, S. (2007). Electrical engineering. Chandni Chowk, Delhi, Global Media. http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=233376. Read More