At this reduced voltage, the core loss can be neglected but the effect of Xm has to be taken into account, as its value is small as compared to that of the transformer. This leads to lower rotor frequency. So for obtaining more accurate value of the rotor resistance, this test is conducted at a lower frequency and then the reactance values are scaled upto 50Hz.
Such kind of a test at low frequency is not necessary for motors of less than 25kw. Name plate ratings of the induction motor to be tested Range of instruments and accessories standard format S.
Name MFR. Activity Sequence No-load Test 1. Turn the variac handle to zero voltage position. Switch on the mains. Gradually raise the variac voltage to start the motor. Set the variac handle to a position so as to feed this motor at rated 3 Phase Voltage. The shaft is held tight so that the rotor is prevented from rotating. With variac in zero position, switch on the mains. Gradually raise the voltage till the motor current reaches full-load value.
In case of a star connected machine anyone of the line terminal and the neutral terminal can be used. But for delta connected machine, the resistance thus measured is a combination of r resistance per phase of delta winding and 2r connected in parallel. The value of r can now be calculated. Induction Motor. Performance can be computed by the following methods. Slip s 0. This is output line. This completes the construction. Table 2.
Results Complete performance characteristics of the given 3ph IM are as shown in graphs. No Load Tests on a Synchronous Generator Preview A synchronous machine can be represented as an equivalent circuit per phase as in Fig. The machine is run at synchronous speed.
We shall adopt heuristic method of correcting Xs for the effect of magnetic circuit nonlinearity. Armature circuit resistance of a synchronous machine can be ignored for voltage and power transfer studies. Of course it has to be accounted for in determination of efficiency. OC Test: The machine is run as generator at synchronous speed with armature terminals open. The plot of Vocl Vs If is the OCC open circuit characteristic which indeed is the magnetization characteristic of the machine.
It exhibits the saturation effects. SC Test: The armature terminals are shorted. The machine is run at synchronous speed while If is gradually increased starting from zero value. The field current being very small this operates in linear region.
Objective: To determine the equivalent circuit parameters of synchronous machine and hence to predetermine the percentage regulation at different power factors. The synchronous machine required to test is mechanically coupled to a shunt motor.
Connect the synchronous machine with dc shunt motor as shown in Fig. OC Test 1. Keep the TPST switch in open state. Start the set by means of the dc shunt motor. Adjust its speed to synchronous value. Include full regulating resistance in the field circuit of the synchronous machine.
Switch on the dc mains to it. The synchronous machine is now running as open circuited generator. Gradually increase If and read line voltage V. Table 9. With the set running at ns, switch off the dc excitation of the synchronous machine.
Switch on the switch TPST to short-circuit the generator terminals. Plot SCC. Record in Table 9. A round flat-bottomed flask of 50ml marking, to measure 50 ml of oil flow against time.
The water bath with oil cup is supported on a tripod stand with leveling screws. C Carbon Tetra chloride and wipe it dry thoroughly with a paper napkins or a soft cloth do not use cotton waste and the orifice jet with a fine thread.
Plot the relevant graphs Heat the water to any desired temperature while continuously stirring the water with the stirring device and occasionally the oil sample with the thermometer. Once the temperature of the oil reaches the required temperature follow steps 6, 7 and 8.
Type of oil used: 2. N Temp. Viscosity varies with temperature and has negative exponential trend. HEAT 5. The apparatus is supplied with two S.
A rubber cork stopper arrangement is provided also at the bottom to facilitate start and stop the oil flow from the Viscometer. Two thermometers are provided to measure water bath temperature and oil temperature under test. A round flat-bottomed flask with a ml marking on the neck is provided to measure 60 ml of oil flow against time.
The oil cup with the water bath is supported on a stand with levelly screws. Clean the oil cup with a solvent preferably C. Keep the water bath with oil cup on the tripod stand and level it. Pour water into the water bath up to 15 to 20mm below the top portion. Close the Orifice opening from bottom with the rubber cork provided. Pour oil to be tested into the strainer by keeping the strainer on the oil cup until the oil fills up in the oil cup as well as in side well. Withdraw the excess oil in the side well and position the thermometers in water bath and oil cup.
Take a clean dry 60ml flask and place it under the orifice jet of the oil cup and center it. Pull the rubber cork open and simultaneously start a stopwatch and allow the oil into the receiving flask. Adjust the receiving flask 60ml in such a way that the oil string coming out of the jet strikes the neck of the flask to avoid foaming formation of air bubbles on the oil surface.
Wait till the oil level touches the 60 ml mark, stop the watch and record the time in sec. Repeat the experiment at different temperatures above ambient. Use specific nozzle suitable for lubricant or oil. NOTE: For conducting experiment at different temperatures above ambient on Saybolt Viscometer, connect the heater of the water bath to a V, 50Hz, 5amps power source through a dimmer stat. The wire is fixed to the torsion head at the top. Adopters are used to adjust the length of the wire.
Surrounding the flywheel, there is a circular scale graduated in degrees. A Cylinder is attached to the flywheel. The instrument is supported on a tripod with leveling screws. The apparatus consists of a device to hold a solid cylinder and a flywheel by means of a Torsion wire with end connectors. A release pin is provided to hold the flywheel in horizontal position.
The flywheel is, surrounded by a graduated scale in degrees 0 0 to 0. A pointer is attached to the flywheel to indicate the angular movement of the flywheel.
Energy Conversion Laboratory Manual 10AEL58 Department of Aeronautical Engineering, DSCE, Bangalore 22 7 Adjust the pointer of the flywheel to zero degree by turning the stationary head either way with absolutely no torsion in the wire and tighten the stationary head.
This angler movement beyond zero over swing is recorded and the viscosity of the oil under test in Redwood seconds is obtained from the graph provided.
OIL 5. In two stroke engines one revolution of crank shaft completes one cycle. Figure shows the timing diagram for a two-stroke cycle engine. It consists of a circle upon which are marked the angular positions of the various cycle events. The diagram is for a vertical engine; for a horizontal engine the diagram would appear on its side. With the two- stroke cycle the inlet and exhaust ports open and close at equal angles on either side of the BDC position.
This is because the piston in this type of engine is also the inlet and exhaust valve, so port opening and closing will occur at equal angles on either side of the dead centre position. Angles shown are representative only. Fix a reference pointer on the body of the engine near the flywheel, Identify the ports. Find out the direction of rotation of the crank shaft.
Mark the opening and closings of the inlet, Exhaust and Transfer ports. Using the protractor fixed on the flywheel, find out the angular position of the piston 6. The valves open slightly earlier and close after that respective dead centre position. The fuel injection also occurs prior to the full compression ie before the piston reaches the dead centre position.
Both the valve operates at some degree on either side in terms of crank angle from dead centre position. When an intake valve opens before top dead center and the exhaust valve opens before bottom dead center, it is called lead. When an intake valve closes after bottom dead center, and the exhaust valve closes after top dead center, it is called lag. On the exhaust stroke, the intake and exhaust valve are open at the same time for a few degrees around top dead center.
This is called valve overlap. E — exhaust camshaft. I — inlet camshaft. P — piston. R — connecting rod. S — spark plug. V — valves. W — cooling water jacket.
Rotate flywheel freely by hand, fix a reference point on the body of the engine near the flywheel 2. Now while rotating, observe piston at TDC Top dead centre and mark with chalk on flywheel with reference to the point 3. Similarly by rotating, mark the position of bottom dead center BDC. It is to be observed that it takes to rotation of flywheel to complete one cycle of operation.
Now identify inlet and exhaust valves. Find out direction of rotation of flywheel crank shaft 6. Bring flywheel to TDC position pointer. Go on rotating flywheel slowly and observe position functioning of both the valves. Now observe when inlet valves opens mark it on flywheel inlet valve open — IVO 9.
Slowly rotate flywheel, and observe when inlet valve closes — IVC. Rotate further observe when exhaust valve opens EVO Using the protractor fixed on the flywheel, find out the angular position of the piston Then draw spiral diagram with data in marking on flywheel.
To reduce the current ripple, we can increase the inductance or the switching frequency. The maximum inductor current is the average inductor current plus half of the current ripple, shown in 6. The minimum inductor current is the average inductor current minus half of the current ripple, shown in 7. Another basic dc-dc converter is buck-boost converter shown in Figure 5.
The output voltage of a buck-boost converter can be either higher or lower than the input voltage. Ratio of the output voltage over the input voltage is shown in 4. Materials and Equipment. Lab Report Requirement. Toggle Main Navigation Main Navigation. Liping Guo Dr. Andrew W. Figure 1. Schematics of a boost converter When the switch is closed, the diode is reverse biased.
Figure 2. Equivalent circuit when the switch is closed When the switch is open, the diode is forward biased. Water is heated by electrical resistance. Pensky martens is a closed cup apparatus. Introduce the thermometer of correct range. Note down the fire point. Energy Conversion Laboratory Manual 1 2. It consists of a cup contains oil is heated by an electrical heater.
Power to the heater is regulated. Insert a thermometer so that it should not touch the bottom of the cup as shown. Note down whether flash occurs or not. THEORY:- Viscosity is the property of fluid which offer resistance between the two layers of fluid when it is moving relative to each other.
From Newton's Law of viscosity. When the oil is used as fuel diesel or furnance oil viscosity is responsible in atomize the fuel into time spray for efficient combustion. Water is heated using electrical resistance. Water is provided with a stirrer so that heat is supplied to oil uniformly and to conduct the experiment at different temperature. At the bottom of viscometer tube an orifice is fitted and the orifice is opened or closed using a ball, which fits exactly to the orifice.
Don't use waste or any dirty cloth. It may block the orifice of the viscometer and close the orifice with the block. Next note down the mass of specific gravity bottle with oil. Energy Conversion Laboratory Manual 4 5. The orifice is closed using a rubber stopper copper cylinder is surrounded by water bath and is heated by supplying electrical power to the heater.
The temperature of water bath and oil is measured using thermometer fitted to it. Close the stopper. Note down the time taken to collect 50cc oil in the specific gravity bottle. Again fill oil into viscometer. THEORY:- calorific value of solid fuel is the amount heat released when 1kg of fuel is burnt, completely expressed in K. The funnel is fitted with cooling coil around it. The cooling water inlet passes through the calorimeter at the bottom and the outlet is at the top.
Thermometers are installed to measure the inlet and outlet temperature of water. The gas is supplied at the bottom and the outlet is at the top. Water is circulated through the coil at constant head. Allow the gas to burn until steady state is reached. Mass is dipped in oil, of which viscosity of oil to be determined. Adjust the viscometer to zero and clamp it.
Rotate the cylinder disc through on revolution i. Release the cylinder to rotate. Note down the angle through which it rotate and also the temperature of the oil. Repeat the experiment for different temperature of the oil and tabulate the results. Energy Conversion Laboratory Manual 10 THEORY:- Valve timing diagram gives the phasing of the valve operation with respect to the angular position of the crank. Figure showing the valve timing diagram for a four stroke cycle engine.
This diagram consists of two circles, one superimposed on the other, since the cycle of four, stroke engine is completed in two revolution of the crank. Inlet and exhaust valve operates before the dead centers. The inlet valve opens before T. C Top dead center and closes after B.
0コメント