He wants to Share his experience & Knowledge and helps technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics. Normally, overheating causes an immense, advanced and permanent contamination. B. Copyright © 2018-2021 BrainKart.com; All Rights Reserved. AC generators work on the principle of Faraday’s law of electromagnetic induction which states that electromotive force -EMF or voltage – is generated in a current-carrying conductor that cuts a … D. 50 cm. Notify me of follow-up comments by email. high voltage transformers are normally used in high voltage laboratory for testing purpose. What is Supervisory control and data acquisition (SCADA)? Generator designers wishes to generate the electric power at high voltages as possible to limit the stator current (for large alternators stator current will be in the order of thousands of amperes) required to achieve the desired output. Home >> Category >> Electrical Engineering (MCQ) questions and answers >> Generation of high voltages and currents 1) The voltage doubler circuit is suitable for the voltage up to a. AC generators have no commutator and can, therefore, be built in very large units to run at high speeds producing high voltages (as high as 11,000 volts), so that the construction and operating cost per kW is low, whereas dc generator capacities and voltages are limited to comparatively low values. Similarly, the stage-III transformer is connected in series with the second stage transformer. The upper most, however, will be a two winding transformer. Save my name, email, and website in this browser for the next time I comment. Generac states that generators less than and equal to 600 volts are medium-voltage and generators greater than 600 volts are considered high voltage. The secondary winding of the second stage transformer is connected in series with the secondary winding of the first stage transformer, so that a voltage of 2V(Double) is available between the ground and the terminal of secondary of the second stage transformer. and it is depending on design. 10:01 AC Generator, Cables, Control Panel, DC Generator, DC Voltage, Electrical Power, Generation System, Power Plant, Scada, Voltage 1 comment Tweet HVDC is used for testing HVAC cables of long lengths as these have very large capacitance and would require very large values of currents if tested on HVAC voltages. The rate of oscillation for the sine wave is 60 cycles per second. A regulating transformer is supplied on the lower voltage side of the test transformer making it able to adjust the magnitude of the output voltage. high voltage transformers are normally used in high voltage … If any query or suggestion about cascade transformer please comment below or Email on Dipak@electricalidea.com. Voltage multiplier is the most common one in these rectifier circuits, and its able to generate up to 3000 kV DC from just 100 kV AC. C. Both a and b. D. None. Alternating voltages are required for most high-voltage tests. The animation below is intended to demonstrate the basic structure of and AC generator and to illustrate the mathematical derivation of induced AC voltages in a 3-phase generator. A common source of DC power is a battery cell There is a point where the voltage level supplied can be so high as to damage a motor but this level is far higher than that for electronics. The currents required for these tests on various equipments are given below: •   Insulators, C.B., bushings, Instrument, •   Power transformers, h.v. The efficiency of AC voltage is high as compared to the DC voltage. The commonly used high frequency resonant transformer is the Tesla coil, which is a doubly tuned resonant circuit shown schematically in Fig. Zpt = leakage impedance measured on primary side with tertiary short circuited and secondary open. Generation of Alternating Voltage The voltage which changes polarity at regular interval of time is known as the alternating voltage. B. Ac voltage generation. Alternating current is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current which flows only in one direction. The primary winding of stage-III transformer is loaded with P and so also the tertiary winding of second stage transformer. The loading of various windings is indicated by P in Fig. The backup generator supplies voltage … The main disadvantage of cascading the transformers is that the lower stages of With this, the weight of the whole unit is subdivided into single units and, therefore, transport and erection becomes easier. The tanks of stage-II and stage-III transformers have potentials of V and 2V, respectively above earth. The flux density chosen is low so that it does not draw large magnetizing current which would otherwise saturate the core and produce higher harmonics. cascade connection of transformer very high voltage is possible to generate at lowest cost. The principle of cascade excitation of transformers, particularly those connected in a circuit in which each transformer in turn is excited from a part of the step-up winding of the preceding transformer, is usually used. 12.2.6 Frequency If the signal in the Figure makes one complete revolution each second, the Therefore, the primary of the second stage transformer would be loaded with 2P. Extending the same logic; it is found that the first stage primary would be loaded with P. Therefore, while designing the primaries and tertiary’s of these transformers, this factor must be taken into consideration. Fig. This experiment examines the generation of High AC Voltage … winding are brought out to be connected to the next stage transformer. Through h.t. Fig. High-Voltage Direct Current (HVDC) Swiss engineer René Thury used a series of motor-generators to create a high-voltage DC system in the 1880s, which could be used to transmit DC power over long distances. This system is an economical solution to connect grids of different frequencies or asynchronous grids, too. Synchronous Impedance or E.M.F. the leads from the excitation winding and the high voltage winding are brought out to be connected to the next stage transformer. With this, the weight of the whole unit is subdivided into single units and, therefore, transport and erection becomes easier. Hence, in order to have a low impedance of a cascaded transformer, it is desirable that the impedance of individual units should be as small as possible. GUJARAT POWER ENGINEERING & RESEARCH INSTITUTE By- -Thawani Karan(58) 2. Generation of high A.C. voltages = 0.5–1 A. A. AC voltage output, high engine speed-high AC output. Even though most of the equipments on the system are 3-phase systems, a single phase transformer operating at power frequency is the most common from of HVAC testing equipment. Fig.3.2. He is Presently work as Senior Design Engineer in Vadodara, India. However, if the high voltage windings are of mid-point potential type, the tanks are held at 0.5 V, 1.5 V and 2.5 V, respectively. A. Dc voltage generation. The difference is that the generated electrical power is rectified to the DC bus for further distribution which has a HVDC bus bar (270 or 540 V). A voltage is available across the secondary of this transformer. Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail. Important Short Questions and Answers: Electrical breakdown is gases, solids& Liquids, Generation of High Voltages and High Currents, Half Wave Rectifier Circuit - Generation of High Voltages and Currents, Cockroft Walton Voltage Multiplier Circuit - Generation of High Voltages and Currents, Series Resonant Circuit - Generation of High Voltages and Currents, Tripping and Control Of Impulse Generators, Important Short Questions and Answers: Generation of High Voltages and High Currents. Comparing to AC systems and used primarily on military vehicles and military aircraft, variable frequency generation with high-voltage DC (HVDC) distribution structure is shown in Fig. Alternating current AC varies in polarity and amplitude. In an AC network the equipment is continuously subjected to full power frequency voltage. GENERATION OF HIGH ALTERNATING VOLTAGES • Cascaded transformers • Resonant transformers • Tesla coil Methods which can be used to generate high a.c. voltage are 4. Also, with this, the transformer cost for a given voltage may be reduced, since cascaded units need not individually possess the expensive and heavy insulation required in single stage transformers for high voltages exceeding 345 kV. 3.9.Here Zp, Zs, and Zt, are the impedances associated with each winding. high voltage transformers are normally used in high voltage laboratory for testing purpose. The total short circuit impedance of a cascaded transformer from data for individual stages can be obtained. If these measured impedances are referred to primary side then. The impedance is the passive parameter of the AC voltage, and for DC it is resistance. Dipak Suthar has completed BE Electrical. Currently you have JavaScript disabled. the impedance of transformer is should be less than 5%. This relationship … This connection results in a cheaper construction and the high voltage insulation now needs to be designed for V/2 from its tank potential. Generators producing 4160 volts are common in many industries for large motors that require high voltage. Two or more electrical transformers connected in series to generate high voltage alternating current. The primary voltage rating is 10 kV and the secondary may be rated to as high as A voltage is available across the secondary of this transformer. He has more than experience in Inspection of Distribution Substation and more than 1 Year Experience in Electrical Projects (Designing-Technical Review-coordination -Execution). it is to be noted that the individual stages except the upper most must have three-winding transformers. 3.9 shows metal tank construction of transformers and the secondary winding is not divided. transformer must be capable for giving a short circuit current for at least more than one minute. The generator generates the AC voltage, and the DC voltage is obtained from the cell or battery. Here the low voltage terminal of the secondary winding is connected to the tank. The generator terminal voltage is then stepped up by the power station transformer to a higher voltage (115 kV to 765 kV AC, varying by the transmission system and by … The main disadvantage of cascading the transformers is that the lower stages of the primaries of the transformers are loaded more as compared with the upper stages. AC is an important part o… Answer c. Q.9 cockcroft walton circuit is used for. Here we see an AC sine wave and we see that it is constantly changing going negative or going positive and then negative. The equivalent circuit of an individual stage is shown in Fig. The test transformers in high voltage labs are used to step up the voltage from a lower AC voltage level to a desired one. In a high voltage laboratory the test transformers steps up the voltage from a lower voltage (220 V or 11 kV) to the desired voltage level. This technology has some better qualities compared to AC power transmission and is the only alternative to high voltage AC transmission. 10cm. As the voltage level goes up, the current is reduced and lower current usually equates to less heat generation within the motor windings. The potential of the excitation is fixed to the potential of the secondary winding. The tanks of stage-II and stage-III transformers have potentials of V and 2V, respectively above earth and, therefore, these must be insulated from the earth with suitable solid insulation. The upper most, however, will be a two winding transformer. He is Technical Blogger and Familiar with English, Hindi, Gujarati languages. The tertiary winding (excitation winding) of first stage has the same number of turns as the primary winding, and feeds the primary of the second stage transformer. Rectifier circuits, which will convert the high voltage AC to high voltage DC. For the three-stage transformer, the total output VA will be 3VI = 3P and, therefore, each of the secondary winding of the transformer would carry a current of I = P/V. This connection results in a cheaper construction and the high voltage insulation now needs to be designed for V/2 from its tank potential. The reason is fairly simple. Test transformers normally used for the purpose have low power rating but high voltage ratings. Assuming negligible magnetizing current, the sum of the ampere turns of all the windings must be zero. For voltages higher than 400 KV, it is desired to cascade two or more transformers depending upon the voltage requirements. With this the output voltage between ground and the third stage transformer, secondary is 3V. capacitors. These transformers are mainly used for short time tests on high voltage equipments. The primary and the secondary are wound on an insulated former with no core (air-cored) and are immersed in oil. Refer to WESTERBEKE' S operators manual or service manual for engine speed/hertz adjustment or for other possible engine related problems. Answer a. Q. A voltage supplied by a battery or another DC sourcehas a certain polarity and remains constant. The impedances are shown in series with an ideal 3-winding transformer with corresponding number of turns Np, Ns and Nt. Actually for getting such high voltage, a single transformer has to be very huge in size which is not at all economical. How Transformer Tap Changer actually control the voltage?? And the direction of a half cycle changes after every particular interval of time. 11:03. rules that apply to voltage, current, and power in a DC circuit also apply to the AC circuit. 5cm. C. 15 or 25 cm. It is found that the cost of insulation for such voltages for a single unit becomes proportional to square of operating voltage. Similarly, the stage-III transformer is connected in series with the second stage transformer. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. A. Dc voltage generation. The peaks are indeed at 170 volts; it is the effective (rms) voltage that is 120 volts. Nikola Tesla -Inventor of A.C Generator GENERATION OF ALTERNATING CURRENT 3. Do you know how you can Generate Electrical Energy by Foot…. All laboratory tests are single phase and the low voltage side of the transformer is supplie… Ohm’s law formula for an AC circuit may be stated as R V I eff eff = (12.8) Importantly, all AC voltage and current values are given as effective values. The tank of stage-I transformer is earthed. 10 cascaded transformer is used for. But find it too compacted or difficult to … Oscillating power like this is generally referred to as AC, or alternating current. Most students of electricity begin their study with what is known as direct current (DC), which is electricity flowing in a constant direction, and/or possessing a voltage with constant polarity. 24.9. The secondary winding of the second stage transformer is connected in series with the secondary winding of the first stage transformer, so that a voltage of 2V is available between the ground and the terminal of secondary of the second stage transformer. bushings, the leads from the tertiary winding and the h.v. Click here for instructions on how to enable JavaScript in your browser. therefore, these must be insulated from the earth with suitable solid insulation Through high voltage bushings. The tank of stage-I transformer is earthed. •Alternating Current: An alternating current is the current which changes periodically both in magnitude and direction. This paper presents a high-frequency high-voltage generator which generates a high voltage up to 30 kV peak in the frequency range of 1 kHz to 50 kHz for basic dielectric investigations and high voltage tests of equipment. However, due to the high cost and maintenance of the Thury systems, HVDC was never adopted for almost a century. DC is the kind of electricity made by a battery (with definite positive and negative terminals), or the kind of charge generated by rubbing certain types of materials against each other. The alternative to AC is DC, or direct current. What could happen if a generator’s output voltage is too high A voltage that is too high could potentially trigger overheating which could ultimately lead to early failure in different electronic and electrical items. A simplified generator is shown on the left. Most of the present day transmission and distribution networks are operating on a.c. voltages and hence most of the testing equipments relate to high a.c. voltages. 3.9 shows a basic scheme for cascading three transformers. 9. The primary of the stage-I transformer is connected to a low voltage supply. Before testing, get a clear explanation of the problem that exists, be certain it relates to generator components. With this the output voltage between ground and the third stage transformer, secondary is 3V. The one complete cycle of an alternating quantity consists two half cycles. The impedance means the opposition offered by the voltage to the flow of current. It has been observed that the impedance of a two-stage transformer is about 3–4 times the impedance of one unit and three-stage impedance is 8–9 times the impedance of one unit transformer. 3.9. Although the AC power transmission technology performs generation … In order to post comments, please make sure JavaScript and Cookies are enabled, and reload the page. The transformers are usually identical, but transformers of different designs can also be used. The investigations are performed either directly with this type of voltage, or used in circuits for the generation of high DC voltage and impulse voltages. Generation of High Voltage AC using Cascading of Transformer - Duration: 11:03. The equipment should therefore be able to withstand power normal frequency voltage, allowing for some overvoltage. You have entered an incorrect email address! Two or more electrical transformers connected in series to generate high voltage alternating current. The excitation winding (tertiary winding) of first stage has the same number of turns as the primary winding, and feeds the primary of the second stage transformer. The rating ... High Frequency AC Generation. high voltage winding of the first transformer at its high voltage end. Generating AC Voltages Generator Principles. 2V High Voltage DC technology is an effective and technical solution for the transmission of power over very long distances. The primary of the first stage transformer is connected to a low voltage supply. The impedances are obtained either from calculated or experimentally-derived results of the three short circuit tests between any two windings taken at a time. Generation of high A.C. voltages Most of the present day transmission and distribution networks are operating on a.c. voltages and hence most of the testing equipments relate to high a.c. voltages. 6.13a. High Voltage High Voltage AC Generators Kato Engineering high voltage generators range from 6000 - 15,000 V. The specially designed insulation system used on Kato generators guarantees high opposition to chemicals and moisture in hostile environments, and long generator life. 3.8. Most of the present day transmission and distribution networks are operating on a.c. voltages and hence most of the testing equipments relate to high a.c. voltages. Q.8 to measure a high voltage of peak value about 150kv, the suitable. The design of a test transformer is similar to a potential transformer used for the measurement of Voltage and power in transmission lines. The potential of the tertiary is fixed to the potential V of the secondary winding as shown in Fig. Each of the three - coils generates an AC voltage sine wave as illustrated in Figure 4a and 4b The voltage wave (phase) B begins one third of the way into the A wave cycle, and the C wave begins two thirds of the way into the A wave cycle. We looked at that in our discussion of DC and we looked at battery connected to something and we saw that it had a positive polarity and a negative polarity and it remained constant, it did not change. current. For voltages higher than 400 KV, it is desired to cascade two or more transformers depending upon the voltage requirements. Method for finding a Voltage Regulation, Determination of Xd and Xq Using Slip Test, AC voltage regulator (AC to AC converter), Cascaded transformer unit with isolating Transformer. 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