Engineering, Polytechnic and Vocational Training Equipment-> Electrical Engineering Laboratory

1 [2] 3 [«Back ||Next »]   Click to Enlarge PATCH PANELS Patch panels are the connector panels, used to interconnect various machines to meters, rheostats, Variac and others, which are used in a machines lab. This is only another way, to increase the safety for the personnel, conducting the experiments. The connections from each machine are terminated on this connector panel. The necessary wirings from the machine to these panels are to be securely made, prior to, conducting lab experiment. Each panel is diagrammatically represented to reflect various terminals of a machine, and they are printed above the terminals. All the necessary terminals of the machine are terminated on a 4mm patch cord terminal, suitable to make interconnections with other associated circuitry. Each connector panel differs from the other panel in terms of drawings used for different machines. We supply these, as part of a turnkey project, while setting up the machines lab. The pictures shown here, describe how each panel is represented. These are the panels, which are placed on the experimental table. The 4mm terminals from these are used for interconnecting with other associated circuitry. See Enlarge Click to Enlarge LABORATORY RECTIFIER UNIT These laboratory rectifiers are mainly used in electrical engineering laboratories for the purpose of conducting experiments in machines and DC circuits. This is servo controlled to provide constant DC output. This provides 100A output for continuous operation. This rectifier provides suitable source for operating DC machines. System Description: This rectifier works with 3 phase 415V AC as its mains supply voltage. The ripple factor is less than 5% at its peak load. The DC output from this unit is continuously variable by a potentiometer, in the range of 200 to 240 DC. A servo control motor circuit ensures constant DC output voltage. A digital voltmeter and Suitable HRC fuses are provided at AC input and DC output stages for protection. The rating of the mains transformer is designed to provide upto 200V DC, while the series transformer provides 40V DC, suitably arranged to provide the correction required. The series transformer is controlled by a three phase motorized dimmerstat. The rectifier circuit is generously rated with suitable heat sink and hole storage suppression. This unit has a START and STOP push buttons. Pressing Start push button makes, the output to set at the voltage shown by the panel meter, and the output is available at the terminals at this time. Pressing stop push button, the output is reset to 0V. In the event of mains power failure or accidental break in the mains supply, the DC supply from this rectifier unit, is automatically disconnected. The output from this rectifier is available to the DC circuit, only when the mains power returns AND start push button is pressed. This facility provides the scope for investigating the reason for the failure, and also protecting the assets. The entire rectifier unit is assembled in a rugged sheet steel material with suitable reinforcements wherever required. The entire unit is assembled on suitable caster wheels, to provide mobility for unit. See Enlarge Click to Enlarge 15A LABORATORY RECTIFIER These laboratory rectifiers are mainly used in electrical engineering laboratories for the purpose of conducting experiments in machines and DC circuits. This provides constant DC output. This provides 15A output for continuous operation. This rectifier provides suitable source for operating DC machines or any DC circuit. Suitable fuse protection is provided. The analog panel meters mounted on the front panel can monitor the output voltage and the current. This has a START and STOP push buttons. When start button is pressed, the DC voltage is available at the output terminals, as indicted by the meter reading. When stop button is pressed the output is reset to zero. In the event of mains power failure or accidental break in the mains supply, the DC supply from this rectifier unit, is automatically disconnected. The output from this rectifier is available to the DC circuit, only when the mains power returns AND, the voltage setting Variac is brought to 0V position AND start push button is pressed. This facility provides the scope for investigating the reason for the failure, and also protecting the assets. Specifications: Input : 230 V AC single phase Output : 230 V DC continuously variable from 0 to 230V with suitable START Interlock. Capacitry : 15A Meter : Voltmeter and current meter indicators. Switches : START and STOP switches. Output control : DC Mains ON/OFF switch. NOTE: You must connect ELCBs, earth connections, fuse switch gear, all other protective methods must be implemented, wherever required. See Enlarge Click to Enlarge DISTRIBUTION PANELS Distribution panels are intended to provide necessary AC or DC supplies to the AC or DC machines. There are two different distribution panels available. These are classified as AC distribution panel or DC distribution panel. The AC supply (three phase) to an AC machine is routed through AC panel, and while DC supply is routed through DC panel. This is similar to a distribution board, in function. Each machine gets its AC or DC supply either from the mains or from the rectifier unit respectively, through these panels only. I.e. the supply for each machine is routed through this distribution panel. The supply to each machine is suitably switched ON / OFF through a suitably protected MCB. This provides protection to each machine. Routing supply through these panels allow you to switch ON or OFF using respective switch gear, there by power can be saved, permitting you to switch ON the machines which are required for experimentation, and switching OFF the remaining machines. Specifications: 1. DC Distribution Panel: 1. Input: DC voltage input 230V DC from the 100A rectifier unit. 2. Output: 230V DC to respective machines 3. Meters: DC Voltmeter and DC current meters are used. The DC meter indicates the overall DC voltage available to the DC circuits. There will be line drop at the respective machines, when measured near the machine. This is due to line loss. The current meter indicates the total current drawn by the whole DC circuit through this panel. 4. Switches: 12 different DC circuits can be connected through this panel. Each circuit is protected with an independent MCB. In addition to this a master switch controls the complete DC circuit. When this is in OFF position, the DC supply to all the DC circuits are switched OFF. 5. A lamp indicator is used to display the status of power supply. This is illuminated when the power is ON. 6. Separate earth connection is provided to the panel. This must be securely connected to the Earth. 7. Enclosure: This is assembled in a sturdy cabinet, using sheet steel. 8. Assembly: This has to be assembled on a rigid foundation next to the DC rectifier unit. NOTE: You must connect ELCBs, earth connections, fuse switchgear, all other protective methods must be implemented, wherever required. See Enlarge Click to Enlarge EXPERIMENTS IN ELECTRICAL ENGINEERING All the electrical engineering experiments will have broadly the following objectives while performing relevant experiments. The scope of the supply does not include, hardware like DOL starters, Mains switches, wiring from the mains supply to the experimental tables, HRC fuse assemblies, Circuit breakers, ELCBs, civil structures etc. However these are required to be installed or constructed or assembled and wired, prior to connecting necessary experimental setups. Objectives of experimental setups. a. Activity Sequence b. Study of nameplate details c. Identifying measuring instruments and support accessories required for conducting the experiment d. Preview e. Record Circuit Diagram and connection diagrams f. Model graph and expected outcome g. Data processing and calculations and h. Inference While establishing the electrical laboratory, the following recommendations may be adhered at the experimental tables, as a precautionary measure. ?Separate wires and neutral wires using standard 7-20 SWG, must be drawn from MCBs on the distribution panel to the respective Motor ? Generator / Alternator sets. ?Mains trip switch (Isolators) for DC and 3 ?, to be provided near every equipment MG Set of each experimental setup for safety purpose. ?Neutral must be terminated with 30A black color banana terminal, at each and every experimental work table ?Earth wire using 8 SWG copper wire must be made available at every MG set. At least two bolts on the base assembly of MG set must be connected to this earth wire. ?Isolators must be fitted as shown in the diagram near each and every MG set. UNENDING DEBATE: How do you distinguish and qualify a component, or a machine or an experimental setup, suitable for Electrical engineering laboratory and why? There was a growing concern expressed by various learned faculty members, that power-handling capabilities of the machines recommended for laboratory experiments should reflect, close to qualify for true Electrical engineering laboratories. This is partly because, true electrical characteristics of systems will be better observed and more pronounced in higher power handling ranges, than in the machines working at few hundred watts. This remained always a point of discussion and debate, with differing views by many learned faculty members. For example, one faculty member says it is sufficient if rudiments of electrical engineering are explained to the students at graduate level, so that we need not invest big money. The other faculty member differs, stating that, it is something like teaching swimming without a swimming pool to a trainee / student. Further, he goes on to say that, the student / trainee cannot feel the strain and pain without actual swimming in the pool. So it looks, the characteristics of an electrical machine, will look more pronounced and meaningful, if it is atleast close to a KW region. The arguments and counter arguments are unending. It looks, power handling capabilities, probably appears to be the point in argument, to qualify a component or machine or a setup to be used in electrical engineering laboratories. Atleast this appears to be the consensus by various faculty members in electrical engineering. For example, a transformer used in an electronic measuring instrument can be anywhere between a few watts to say hundred watts. When such a transformer is used in electrical engineering experiment, no doubt, it is sufficient to explain the rudiments of a transformer. But when it comes to electrical engineering labs, a KW appears to be a normal parameter, while it is a few tens of watts or at the best say 300 watts, when used by an electronics engineer. This is because an electrical engineer is tuned to handling power systems or must be trained to handle large power. Hence the power handling capabilities of the machines appear to be the necessary evil. Experimental setups made in modular style, looks small and compact. They are economical, but the power handling capabilities of such systems, will not exceed more than say 250Watts. At such low power handling, true electrical experimental characteristics can be realised, Experimental setup required for popular experiments are listed below. This is not a comprehensive list. There is ample scope for listing plenty of experiments. These are minimum requirements, listed in various university syllabi. specific request. It is very important for you to incorporate all the necessary safety features against accidents that may occur during the experiments. See Enlarge Click to Enlarge EXPERIMENTS ON TRANSFORMER SINGLE PHASE TRANSFORMER (OPEN CIRCUIT AND SHORT CIRCUIT TEST) Transformer is the very first electrical that is required in making any electrical equipment. This component in turn provides the overall power required, for any system to operate successfully, after necessary isolation, step/up or step/down conditions, as required in the final system. Hence this is the most critical and useful part of any electrical equipment. Therefore it is important to study, understand and experiment, a process, for evaluating its operating characteristics. This knowledge will be utilized, when an engineer is required to design, troubleshot and maintain any electrical system. Suitable HRC fuses are provided at AC input and DC output stages for protection. The rating of the mains transformer is designed to provide upto 200V DC, while the series transformer provides 40V DC, suitably arranged to provide the correction required. The series transformer is controlled by a three phase motorized dimmerstat. The rectifier circuit is generously rated with suitable heat sink and hole storage suppression. Objective: Determine the parameters of the equivalent circuit of a single-phase transformer, and to predetermine the performance characteristics and verify the specifications by open circuit and short circuit tests. 1. Study of nameplate ratings of the transformer under test. 2. Determination of Voltage ratio (Turns ratio) test 3. Performing an Open Circuit (OC) Test 4. Performing Short Circuit (SC) Test 5. Determination of Efficiency of the transformer. 6. Draw a graph of performance at UPF and at 0.8p.f.lag. 7. Predetermination of Regulation of Transformer Scope for inference As the transformer is inductive load, it takes large in rush current. Select proper fuse rating. Prefer OC test on LV side and SC test on HV side for personnel safety and meter range. On No load, the p.f. of the transformer will be very low. Hence for better results choose LPF wattmeter. During SC test, low voltage is applied, the LV side is shorted by an insulated wire, use proper connection and proper wire. Always switch OFF the supply after taking readings and then start calculations. Do not increase the input voltage beyond the voltage rating of the transformer. See Enlarge Click to Enlarge SUMPNER?S TEST EXPERIMENT Objective: To perform Sumpner?s test. Predetermination of performance characteristics and equivalent circuit of single-phase transformer. Preview: In OC and SC tests a transformer is subjected to either core loss or copper loss and so these tests cannot as such be used for heat-run for heat-run-test. A heat-run test can be conducted on two identical transformers by connecting them back-to-back. Wherein, their secondaries are connected in phase opposition. So the secondaries will behave open-circuited when the primaries are excited, the current drawn from V1 source being 2I0 providing core losses (2P0) of the two transformers. A low-voltage variable source V2, is connected in the secondary circuit which causes circulating current in the secondaries with primaries acting as short circuit for this source (use superposition theorem). This circulating current can be adjusted to full-load value. The power injected by this source is 2PC, the full-load copper loss of both transformers, while the impedance seen by it is 2Zeq. Both the transformers in this test are thus subjected to full load core and copper losses by phantom loading, while drawing only core loss power from source V1 and only copper loss power from source V2. In some sense this test has similarity with the Hopkinson?s test on two identical dc machines. Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format) 1. Transformer 1? 1KVA Capacity, Primary: 230V Secondary: 115V ? Two numbers 2. Suitable Variac 3. Suitable digital ammeters of different ratings AC 4. Suitable digital voltmeters of different ratings AC 5. Suitable digital wattmeter See Enlarge Click to Enlarge SCOTT CONNECTION EXPERIMENT Objective: To obtain Two-phase supply from Three-phase and to conduct load test. Preview: The concept of 3phase to 2-phase connection follows from the voltage phasor diagram of balanced 3-phase supply. If the point M midway on Vbc could be located then VAM leads Vbc by 900. A 2-phase supply could be thus obtained by means of two transformers; one connected across AM, called the teaser transformer and the other connected across the lines B &C. Since VAM = ?3Vbc/2, the transformer primaries must have ?3N1/2 (teaser) and N1 turns;this would mean equal voltage / turn in each transformer. A balanced two phase supply could then be easily obtained by having both secondaries with equal number of turns N2. The point M is located midway on the primary of the transformer connected across the lines B & C. The connection of two such transformers, known as the Scott Connection, is shown in Fig with its phasor diagram of two phase supply in the secondary. Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format) 1. Transformer 1? 1KVA Capacity, Primary: 230V(tapings at 86.6%,50%), Secondary: 115V ? Two numbers 2. Suitable Loading rheostat for the above single phase ? two numbers 3. Suitable Variac ? three phase 4. Suitable digital ammeters of different ratings AC 5. Suitable digital voltmeters of different ratings AC 6. Suitable digital wattmeter See Enlarge Click to Enlarge EXPERIMENTS IN MACHINES LAB NO LOAD TESTS ON A DC SHUNT MOTOR (SWINBOURN?S TEST) Objective:To determine the performance of the given DC shunt machine in both generator and motor modes of operation Preview: Swinburn?s test is a no-load test on a dc machine. The machine is started and run as a dc motor with shaft decoupled from any load. In this regard the test is very easy to carry out for a machine of any size, particularly convenient for a large machine. The input to motor at no-load comprises of: Iron losses (Pi) Mechanical, friction and windage loss (Pwf) Field Copper Loss (Pshf) Armature Copper Loss (Armature resistance is measured by drop test and corrected to operating temperature of about 750C) Stray load losses are estimated to be 1% of kW rating of the machine at full ? load and considered proportional to square of armature current. With the above data the machine performance at any load (or a set of loads) can be predetermined either as motor or generator. Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format) 1. 2HP DC Motor 220V 2HP 1500rpm with standard screen protected/drip proof (IP21) 2. 3-4 Point DC starters with protectors. 3. Suitable Digital Voltmeter DC to measure voltage across armature 4. Suitable Digital Ammeter DC to measure filed current. 5. Suitable Digital Ammeter DC to measure armature current. 6. Suitable Digital Tachometer to read RPM of the motor. 7. Suitable Rheostat for Armature circuit. 8. Suitable Rheostat for field circuit. 9. Rectifier Unit 0-240V DC @ 1.5KVA with power failure protection. See Enlarge Click to Enlarge SPEED CONTROL OF DC MOTOR BY ARMATURE & FIELD CONTROL Objective: obtain the speed control characteristics of a dc motor at no load. Preview: The dc motors are in general much more adaptable speed drives than ac motors. The speed of dc motors depends upon the following relation. Since the speed is proportional to the ratio between the back EMF and the flux per pole. The back EMF can be varied by varying the armature applied voltage (called as armature control). The flux per pole can be varied by varying the field current (called field control). Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format) 1. 2HP DC Motor 220V 2HP 1500rpm with standard screen protected/drip proof (IP21) 2. 3-4 Point DC starters with protectors. 3. Suitable Digital Voltmeter DC to measure voltage across armature 4. Suitable Digital Ammeter DC to measure filed current. 5. Suitable Digital Ammeter DC to measure armature current. 6. Suitable Digital Tachometer to read RPM of the motor. 7. Suitable Rheostat for Armature circuit. 8. Suitable Rheostat for field circuit. See Enlarge Click to Enlarge DC SHUNT GENERATOR NO LOAD TESTS ON DC SHUNT GENERATOR Open Circuit Test Objective: To obtain the magnetization characteristic and therefrom determine the critical field resistance and critical speed of the given dc shunt generator. Preview: The EMF induced in a DC machine is proportional to the flux per pole, the number of conductors and speed. This EMF depends on speed and flux. As the flux increases the EMF increases beyond a point the flux gets saturated. The BH curve of the core depicts the magnetization curve of the machine. (A) Critical Speed of a DC Shunt Generator Objective: To determine the critical speed of a dc shunt generator. With the fixed excitation and variable speed, as the speed reduces the OCC proportionally slides down so that the no load voltage reduces. At a particular speed, called the critical speed, the OCC is tangential to the Rf line and as a result the generator fails to excite. Preview : With the fixed excitation and variable speed, as the speed reduces the OCC proportionally slides down so that the no load voltage reduces. At a particular speed, called the critical speed, the OCC is tangential to the Rf line and as a result the generator fails to excite. Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format) 1. 2HP Shunt machines mechanically coupled both are identical 220V 2HP 1500rpm. 2. 3-4 point DC Starter for the above 3. Suitable Loading rheostat 4. Digital tachometer 5. Suitable Double tube rheostat 6. Suitable Single tube rheostat 7. Suitable Digital Voltmeter DC 8. Suitable Digital Voltmeter DC 9. Suitable Digital Ammeter DC 10. Rectifier Unit 0-240V DC @ 1.5KVA with power failure protection. See Enlarge Click to Enlarge LOAD TEST ON A DC SHUNT GENERATOR Objective: To obtain external characteristics of a dc shunt generator Preview: The self excited DC shunt Generator is coupled to a DC motor, which acts as prime mover. Two characteristics are more important. The internal or total characteristic that gives the relation between the emf actually induced in the armature and the armature current. This is of interest mainly to the designer. The external characteristics called performance characteristics (also voltage regulating curve) which give the relation between the terminal voltage and load current. This curve lies below the internal characteristics due to armature drop. This is important in judging the suitability of a generator for a particular purpose. These characteristics can be obtained by a load test with total field resistance remaining fixed as the speed is to be kept constant. Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format) 1. 2HP Shunt machines mechanically coupled both are identical 220V 2HP 1500rpm. 2. 3-4 point DC Starter for the above 3. Suitable Loading rheostats 4. Digital tachometer 5. Suitable double tube rheostat 6. Suitable single tube rheostat 7. Suitable digital Voltmeters DC 8. Suitable digital ammeters DC. 9. Suitable DC source ?Rectifier unit See Enlarge Click to Enlarge HOPKINSON?S TEST Objective: To conduct Hopkinson’s test on the given pair of identical dc machines and obtains item performance characteristics Preview: Swinburne’s test on a dc machine is a non-loading test. The machine performance can be computed from the data obtained from this test without actually loading it. In certain situations a dc machine has to be tested by actually loading it particularly for a heat-run test where the machine is fully loaded for a long period to determine its steady state temperature rise. Such a test may not be feasible for machines of even moderate size and such load test even where feasible is highly wasteful of energy for the heat-run test. In a manufacturing concern a number of identical machines may be on production line. Two such machines can be put on a test and coupled mechanically. These machines can then be tested by the Hopkinson’s test where these two machines are connected in parallel across the supply. By adjusting their excitations both of them can be simultaneously loaded (to any extent) where one machine (motoring) feeds mechanical power to the other machine (generating), while the generating machine feeds electrical power to the motoring machine. The only power drawn from the mains is the losses of both the machines. Load test and heat-run test could thus be conducted with very little energy consumption while the machines carry full load current at rated voltage. Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format) 1. 2HP Shunt machines mechanically coupled both are identical 220V 2HP 1500rpm. 2. 3-4 point DC Starter for the above 3. Suitable Loading rheostats 4. Digital tachometer 5. Suitable double tube rheostat 6. Suitable single tube rheostat 7. Suitable digital Voltmeters DC 8. Suitable digital ammeters DC. 9. Suitable DC source –Rectifier unit See Enlarge Click to Enlarge THREE PHASE INDUCTION MOTOR NO LOAD TEST ON A THREE PHASE INDUCTION MOTOR No-Load Test: At no-load the machine runs at very small slip sufficient to provide power for windage and friction loss, core loss and also a certain amount of stator copper loss, which has to be, accounted for because of the large no load current. With low slip, the following approximation will hold good. R2?(1/s-1) is very high R2?/s>>X2? With these approximations the necessary formulae for finding out Xm will be given while conducting the no-load test. See Enlarge Click to Enlarge BLOCKED ROTOR TEST Blocking the rotor from rotating is equivalent to making s=1 so that R2?(1/s-1)=0. This test is conducted by applying a low voltage to the stator so as to limit the current drawn to its full load value. 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. The slip of induction motor during normal operating conditions is low (2 to 8%). 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. Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format) 1. Squirrel cage induction motor 3HP 440V 1440rpm coupled with DC shunt generator 220V@1500rpm 2KW on a common base plate 2. DOL starter (ON line starter for 3? induction motor ) 3. Suitable loading Rheostat single phase 4. Suitable Rheostat 5. Suitable Digital Voltmeter AC 6. Suitable Digital Ammeter AC 7. Suitable Wattmeter 8. Suitable Voltmeter DC 9. Suitable Digital Ammeter DC 10. Digital tachometer 11. 3? 6A capacity Variac 400V / 0-470V. See Enlarge 1 [2] 3 [«Back ||Next »] Go to Top