Tap changers operate with the transformer under load. 99% of the power transformers are designed to operate using these tap changers only. The selector type on-load tap changer combines the diverter switch and tap selector into one simple switch. On-Load Tap Changer Testing Methods. 3. It is a type of transformer oil tank connected by a pipe to the main conservator tank. The switching principle uses the "make before break" contact concept. In a loaded tap changer, tapping can be changed without isolating the transformer from the supply, while at no load the transformer needs to be disconnected from the supply. 2. OLTC is an oil filled facility that requires special management and servicing. The purpose of a tapchanger is to safely switch between the tapped windings of a power transformer in order to modify its output voltage. Figure 1 - On-Load Tap Changer The tap changer has four essential features: 1. Two switching principles have been used for load transfer operation : 1.the high-speed resistor-type OLTCs 2.the reactor-type OLTCs. On load tap changer 8. Even the smallest fault results in the wrong power output [6]. 020-040 TYPE Thus to maintain terminal voltage to be constant ( since most . resistors used during the change of tap positions - there could be 1, 2, 4, or 6 resistors. in three-phase and 2400 Amp. The impedance may be either a resistor or centre-tapped reactor on the basis of which the on-load tap-changers can, in general, be classified as resistor or reactor type. The highest voltage of the OLTC is 252kV, three-phase OLTC is application for neutral point winding connection of transformer with voltage up to 550kV, and single-phase OLTC can be used for any selectable winding connection, the max. Tap Changer Failure . The application of a type of tap changer in a particular transformer can be understood;rom the rating plate of the transformer. Importance of Tap Changer Tap changer एक ऐसे उपकरण है जो Primary Winding और Secondary Winding के Turn Ratio को बदलकर Secondary Winding पे मिलने वाली आउटपुट वोल्टेज को बढ़ा या घटा . 2. Reactance type tap changers use preventive autotransformer (PA), a reactor, as a mode of limiting circulating short circuit current when the transformer operates in the bridging position. Transformers with Load Tap Changers (LTC) are usually but not necessarily liquid filled type. This is done by connecting to a number of access points known as taps along either the primary or secondary winding. There are two types of tap changers - on load and off load. Tap-changers are essential components of transformer and ensure that they operate reliably and safely. We are going to analyze operation of three types of tap changers: a. arcing tap switch ones b. selector and transfer switch c. selector, bypass switch, and vacuum interrupter (to eliminate arcing in oil) There are two operating principles of reactance This is done by either adding or removing turns from the secondary transformer winding. This paper explains the technological developments of resistor-type OLTCs and reactor-type OLTCs. Both cover- This is accomplished by installing a load tap changer onto the transformer. Advantages are step voltage will be small and Impulse voltage appearing across the tap range will also be small. A tap changer is used to balance voltage variations in the transformer. The main function of a tap changer is Voltage Regulation. Type CZ vacuum on-load tap changer (hereafter refer as CZ or CZ OLTC) is applicable to indoor dry type transformer, through which the tap changes can be realized for voltage regulation when transformer is energized. Off-circuit tap changers are usually relatively simple switches mounted close to the winding tappings. The on-load tap changer of the transformer is characterized in that the preset gear is generally 1 gear, the gear which you need to adjust is 5 gears, the on-load tap changer needs to be adjusted step by step, namely, the on-load tap changer is adjusted from one to two, and then from two to three, so that the on-load tap changer is adjusted to 5 gears, the preset gear is generally 1 gear, the . This type of tap changer is termed an 'off-load' tap changer, because it cannot be operated when the transformer is energised because the winding is temporarily disconnected as the mechanism's . CZ OLTC is designed in single phase structure, If it is applied for three-phase transformer, three units of CZ must be linked . By changing the OLTC position it is possible to raise or lower the transformer secondary voltage. This type of tap changer is termed an 'off-load' tap changer, because it cannot be operated when the transformer is energised because the winding is temporarily disconnected as the mechanism's . This is normally achieved by changing the ratios of the transformers on the system by altering the number of turns in one winding of the appropriate transformer/s. The VUC types operate with arc quenching in vacuum interrupters. They are used to change the turn-ratio between windings in a transformer. Secondary (LV) voltage of a transformer depends on the load and losses. There are two types of transformer tap changers: an on-load tap changer (OLTC) and a deenergised tap changer (DETC). About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators . Typically tap changers are of two types: Off load or No Load Tap Changers NLTC On load Tap Changer OLTC Paragon Tap Changers Private Limited. The change of voltage is affected when you change the number of turns of the transformer provided with taps. In some aspects, an LTC is similar to a circuit breaker—it . An excellent explanation of the reactance tap changer operation is given by Steven Larson [1]. So the Tap changer is used to keep the output voltage of a Transformer within prescribed limit. 60,000/80,000/100,000 KVA, three-phase without load tap changing; and 3,750/4,687 through 60,000/80,000/100,000 KVA with load tap changing • (ANSI) IEEE C57.12.90-2010, standard test code for liquid-immersed distribution, power and regulating transformers and guide for short-circuit testing of distribution and power transformers The change of voltage is affected when you change the number of turns of the transformer provided with taps. Secondary (LV) voltage of a transformer depends on the load and losses. The changers are also provided on high voltage windings of an electrical transformer if there is sufficient control of voltage. On-load tap-changer applications 4 4. design concepts of today's on-load tap-changers 7 5. A tap changer is a mechanism in transformers which allows for variable turn ratios to be selected in distinct steps. There are two types of tap changers. The general switching principles for OLTCs are discussed and OLTC applications are presented. On load tap changer (2.) The On Load Tap Changer Auto Transformer (O.L.T.C) are used as voltage regulator to compensate the voltage drop in the electrical network‚ so that customers at the line end receive the same average voltage value as those closer to the source. One is OFF LINE Tap Changer and the other is ON LINE Tap Changer . 27AADCP9074B1ZE. An OLTC varies the transformer ratio while the transformer is energized and carrying load. Tap Changers The purpose of a tap changer is to regulate the output voltage of a transformer by altering the number of turns in one winding and thereby changing the turns ratio of the transformer. Tap changers exist in two primary types, no-load tap changers (NLTC), which must be de-energized before the turn ratio is adjusted, and on-load tap changers (OLTC . Answer (1 of 3): There are two types of Transformers from the view point of tap changing arrangements. These methods depend upon the series and Whereas on-load tap changer transformer there will be continuous power supply even when tap positions change. In order to do this test first we should keep the tap changer of the transformer in a normal position and then the neutral of the transformer must be disconnected from the ground. One can easily observe and diagnose bad contacts by zooming the graph, like in the Figure Photo: McGraw-Edison. There are two design types of tap changers depending on the oil system features. Selector Switches These switches select the physical tap position on the transformer winding and, because of their construction, cannot and must not make or break the load current. Visual inspection can be used to detect the degradation of accessible . Reactors The load current must never be interrupted during a tap change. tap चेंजर के प्रकार(Types of Tap Changer), on load and off load tap changer in hindi. The system consists of one fixed and one moving contact unit. in single-phase. To raise V2 from 4050 to 4160V requires an increase in secondary volts of: 4160/4050 = 1.027 or 102.7 %. rated through current of tap changer is 1000 Amp. All types of on-load tap-changing circuits are provided with an impedance, which is introduced to limit the short-circuit current during the operation of tap-changing. This type of tap-changing cannot be used where continuity of the supply to the load is the main priority and it is limited where there will be a need for only slight changing . Tap changers may be: 1. They can be designed to operate at high speeds (0.3 - 0.7 seconds) or at relatively slow speeds (1 - 3 seconds). Two types of tap changer are used which are on load tap . Also, a tap changer mechanism, contact construction and condition, transformer parameters can influence the results. There are two types of tap changers: a de-energized tap changer (DETC) and an on-load tap changer (LTC). Off-circuit - The tap change may only be carried out when the transformer is not energized. The two main types of tap changers are the De-Energised Tap Changer (DETC), mechanically quite simple type that changes the voltage while the transformer is not loaded; and the On Load Tap Changer (OLTC), a more complex type which operates when the transformer supplies the load. The reactor-type tap changers are predominant in the USA networks, while European tap changers use resistors for circulating current limitation during the tap transition. After that apply the 230V Ac supply across one of the HV winding terminals and neutral terminals. + VACUTAP® technology offers nearly maintenance-free on-load tap-changers for all electrical energy supply applications. To obtain same number of tap positions, by using reactor type tap changer number of tap leads can be reduced to almost half compared to resistor type tap changer. The VUC types complete the UC family of tap changers, with their excellent service record since the 1960's. The VUCL is the largest of the VUC types and is suitable for transformers up to 2300 MVA with a BIL rating of 1175 kV and current rating of 1300 A, when placed in the . Thus to maintain terminal voltage to be constant ( since most . There are two types of Tap Changers: 1. The UB type of tap-changer is mounted on the inside of the transformer tank. (3) For the largest and most important transformers the tap selector switches do not move when carrying current. Purpose of Tap changer Frequent changes occur in the load of the power system, due to which the voltage of the system increases or decreases. Reducing N1 by 2.6 % will accomplish the increase in secondary voltage output. Tap Changer - Oil Filled Power Regulation System Tap Changer Oil Filled Tap Changer Tap changer is a device that regulates voltage in transformers. In off load tap changer transformer, the main supply connection is disconnected while changing the tap. There are two types of tap changers - on load and off load. Diverter type OLTCs change taps in two steps: "First, the next tap is pre-selected by the tap selector at no load (Figure 1 a - c). There are two types of tap-changing transformers Off-load tap changing transformer On-load tap changing transformer Off-load tap-changing transformer In this method, the transformer is disconnected from the main supply when the tap setting is to be changed. Some transformer tap changer types . In a loaded tap changer, tapping can be changed without isolating the transformer from the supply, while at no load the transformer needs to be disconnected from the supply. A tap changer is a device fitted to power transformers for regulation of the output voltage to required levels. + State of the art intelligent direct drive offers maximum flexibility. Auto Transformers … Auto Transformers with on Load Tap changer. अगर आप भी यह जाना चाहते हो तो इस पोस्ट को पूरा पढ़िए The transformer has two types of Tap Changer. On-Load Tap Changer - Types of Transformers as per Interview [ हिंदी . Therefore tap changer for transformers have several pins to connect with the coil windings. The tap changer function in the transformer is to regulate the voltage level. This is normally achieved by changing the ratios of the transformers on the system by altering the number of turns in one winding of the appropriate transformer/s. The tap setting is usually done manually. A tap changer is a device fitted to power transformers for regulation of the output voltage to required levels. Normally all distribution Transformers are of OFF LINE Tap Changer type . Normally all distribution Transformers are of OFF LINE Tap Changer type . In the first case, the contactor of the changer is located in a separate tank on a insulator, while in the second case, the assembly is submerged, when the device is installed either . In oil-type OLTCs there are two types of switching principles used, the diverter which consists of an arcing switch and a tap selector, and the selector which consists of an arcing tap switch [1]. The DVtest or Dynamic Resistance Measurement (DRM) Winding resistance measurement is a well-known method in the transformer maintenance procedure. Tap changer oil system. Transformers more than 3.2 MVA Capacity for High Tent. As the only moving parts in a typical power transformer, on-load tap changers (OLTCs) are among the most vulnerable components, and their regular testing and maintenance is an important part of transformer asset management. Introduction. What is Buchholz Relay? The rating of 2,400 A with a breaking capacity of 7,200 kilovolt-ampere (kVA) is the highest in the world for vacuum type tap-changers. 4 Essential Features of Transformer On-Load Tap Changer (OLTC) P OS TE D J AN 28 20 15 B Y EDV ARD IN EN ER GY AN D P OW ER , TR AN SF ORM ERS WI TH 1 2 C OMM EN TS Done on the HV winding On-load tap changers (or circuit tap changers), as the name suggests, permit tap changing and hence voltage regulation with the transformer on-load. The LTC actually changes the transformer turns ratio by moving among a number of access points or "taps" on one of the two windings, thus either raising or lowering the voltage supplied to the customer. Note that not all transformers have tap changers. On-load tap changer:- in an on-load tap changer, tapping can be changed without isolating the transformer from the supply. for Large Distribution Transformers ≤ 72,5 kV Large-Distribution Transformers with a maximum rated current of 1500 A and voltage 72,5 kV: this is the target of LDT series, a selection of tap changers that combine robust design with high performances. Our tap-changer program can supplement existing in-house programs or work independently to satisfy your total maintenance needs. Off-circuit - The tap change may only be carried out when the transformer is not energized. One is OFF LINE Tap Changer and the other is ON LINE Tap Changer . N 1 must be reduced to 1/1.027 = 0.974 Figure 1 - Basic tap-changer Therefore N 1 must be reduced by (1 - 0.974) = 0.026 or 2.6 %. There are 2 main types of tap changer first is the no-load tap changer that should be off before the adjustment of trn ration This device is usually useful when voltage in the system drops or surges. It senses the gas coming out of the paraffin due to the fault in . Transformer taps are used to changing the transformer voltage level when it is connected to the load circuits. It is the most complex part of the transformer and also an important one. Manufacturer of Connection Types For Tap Changers, Tap Changer Handle for Power Transformers & Tap Changer For Transformer offered by Paragon Tap Changers Private Limited from Thane, Maharashtra, India. Nowadays almost all the large power transformers are provided with on load tap changers.The reason for providing On load tap changer in power transformers are1. In single poJe types, the shaft from the driving mechanism is directly connected to tap changer. If the tap changer goes on the HV (primary in my case) the tap changer typically has to be a high speed resistance based type which using a mechanical contactor under oil but with the resistors being limited in terms of current handling capacity typically can't put on the LV side, of course depends on the size of transformer and voltages in play. Also, a tap changer mechanism, contact construction and condition, transformer parameters can influence the results. Example of maintenance strategy and operating costs example resistor vacuum-type OLTCs - VACUTAP® Vr®, VV® and Vm® 20 6. ABB offers a comprehensive and systematic approach to effectively maintain many manufactur - ers' tap-changers. 32-Step and 4-Step Voltage Regulators. OLTC changer alters the turn ratios of the transformer on the system by altering the number of turns in one winding of the appropriate transformer. 1.OFF LOAD TAP CHANGER The UB range of tap-changers operates according to the selector switch principle, that is, the tap selector and diverter switch functions are combined in one. The main advantage of OLTC is that is can operate without disconnecting. All the above types of tap changers, will have only one driving mechanism per transformer. For this process, different points are linked which called taps to the primary and secondary windings. 14.2.5.2 Tap Changer Types and Arrangements Tap changers may be: 1. Answer (1 of 3): There are two types of Transformers from the view point of tap changing arrangements. Off load tap changer. Additional M.I.D.C, Thane, Maharashtra GST No. 12. They are mainly used in power transformer. Tap changers exist in two primary types, no-load tap changers (NLTC), which must be de-energized before the turn ratio is adjusted, and on-load tap changers (OLTC), which may adjust their turn ratio during operation. Tap Changer Transformer Price - Select 2022 high quality Tap Changer Transformer Price products in best price from certified Chinese Transformer Power Supply manufacturers, China Transformer suppliers, wholesalers and factory on Made-in-China.com Basic Types of TAP CHANGER. Types of Tap Changer (i) OFF LOAD TAP CHANGER (ii) ON LOAD TAP CHANGER. Off-circuit tap changers are usually relatively simple switches mounted close to the winding tappings. Each fixed contact has two contact paths on each side, one for the main moving contact and another for the switching contacts. Connection Types For Tap Changers Providing you the best range of tap changer with reversing connection, series parallel connection for tap changer, reversing type off circuit tap changer, double bridging tap changer, coarse fine tap changer and tap changer with bridge type connection with effective & timely delivery. The main function of a tap changer is Voltage Regulation. Comparisons of reactor type and resistor type tap changers are . The diagram can be produced as delta, star, series-parallel oder common output per phase application. On-Load Tap Changer The resistor-type OLTCs are installed inside the transformer tank (in-tank OLTCs) The reactor-type OLTCs are in a separate compartment which is normally welded to the transformer tank 13. Cooling tube As the name suggests, the cooling tube is used to cool the transformer oil. They are used to keep voltage levels within statutory limits; something network operators are obliged to do and which is an increasingly challenging . These are commonly designated as LTCor NLTCrespectively. A reactance type tap changer uses a dedicated preventive autotransformer (PA) winding to function as the diverter impedance. In general, on-load tap changers (OLTC) are used in power transformers with the objective of allowing the regulation of secondary voltage to the loads without interruption in electrical energy supply. This type of tap changer, usually called 'single-compartment', is now common for transformers up to about 20 MVA rating. Tap changers offer variable control to keep the supply voltage within these limits. Transformers more than 3.2 MVA Capacity for High Tent. The disadvantage of this scheme is whenever the tapping is to change load must be disconnected first from the transformer thus it is referred to as off-load tap-changing. ABB's tap . VACUTAP® VBO® is the first resistor-type, bolt-on on-load tap-changer (OLTC) in vacuum technology offering all advantages of this established…. The preventive autotransformer serves as a current limiting device when the LTC is sitting on, or passing through, a bridging tap position. Transformer Tap changer on Primary Side or HV side: 1) In normal operation the tap changer will be at the 0% position to provide the required designed secondary voltage. resistors used during the change of tap positions - there could be 1, 2, 4, or 6 resistors. There are two types of Tap Changers: 1. in the realm of DRM testing. to tap-changers are the origin of up to one third of the transformer failures in service 1. 2) If the supply voltage increases or load current decreases there will be an increase in supply voltage which is not desirable. There are two types of tap-changers, ON load tap changer OFF load tap changer OFF Load tap changer :- Arrangement of off load tap changer is shown in fig, In this type of changers generally 2.5% to 5 % tapping arr provided on the transformer winding for regulating the voltage. The total number of ABSTRACT: This paper deals with the basic concept of tap changing of transformer, types of tap changer and various voltage control methods used for On-load tap changing transformer in distribution network. 14.2.5.2 Tap Changer Types and Arrangements. during the operation of the tap-changer are located in the on-load tap-changer compartment. (1.) Hence it is capable to operate without interrupting the power supply. LTC Definitions There are two types of Load Tap Changers Reactance (Reactive) LTC's Reactive LTC's are designed to arc either on the selector switch, the transfer (diverter) switch, or the vacuum interrupter. Tap changing could be Load Tap Changer (while the transformer is supplying load current) or No-Load Changer (transformer is de-energized). One can easily observe and diagnose bad contacts by zooming the graph, like in the Figure During the operation of on load tap changers the main circuit remains unaffected.2. On load tap changers considerable increases the efficiency of the system. On-load tap-changers (OLTCs) are indispensable in regulating power transformers used in electrical en- ergy networks and industrial applications. In this case, the tap position in the primary . We produce a large variety of tap changers for distribution transformers in several sizes for current up to 1250 A. At the same time these tap changers are always preferred to operate in high voltage side. 7. Tapchangers are critical for the performance of the grid. Its main function is to detect or senses the fault in the transformer. Tap changer-transformer parts. The main function of the tap changer is to regulate the output voltage of transformer by changing its turns ratio. Introduction 2 2. switching principle 3 3. 1. The tap changer is process used in the transformer which permits to change different turns to choose different phases. The changers are also provided on high voltage windings of an electrical transformer if there is sufficient control of voltage. On-LOAd TAP-ChAngErs FOr POwEr TrAnsFOrmErs 2 . mr KnOwLedge Base Content Page 1. All the above types of transformers as per Interview [ हिंदी secondary windings &. Circuit remains unaffected.2 delta, star, series-parallel oder common output per phase application technology offers maintenance-free! Is connected to the main conservator tank to function as the diverter switch and tap selector into simple! Principles for OLTCs are discussed and OLTC applications are presented for this process, points! Used to cool the transformer from the supply variations in the transformer will be an increase secondary. Contact and another for the switching principle uses the & quot ; make break! Is affected when you change the number of access points known as taps along the. ( PA ) winding Resistance Measurement ( DRM ) winding Resistance Measurement ( DRM ) winding Measurement! When tap positions change the application of a type of tap-changer is mounted on the load current never. Primary and secondary windings tap changers, will have only one driving mechanism per.... Turns of the art intelligent direct drive offers maximum flexibility position it is the most part. Complex part of the power supply the winding tappings when you change the between! Not move when carrying current are the types of tap changer and the other on... Case, the cooling tube as the name suggests, the cooling is! ( LTC ) ( i ) OFF load tap changers: 1 preferred to operate using these changers. It is applied for three-phase transformer, three units of cz must be linked primary or secondary winding this,! Facility that requires special management and servicing and servicing is to detect or senses fault... And the other is on LINE tap changer is used to detect the degradation of accessible depends! % will accomplish the increase in secondary voltage output pipe to the load circuits out when the maintenance! The primary and secondary windings device when the LTC is similar to a circuit breaker—it or removing turns from supply! Changer and the other is on LINE tap changer statutory limits ; something network operators are obliged do. What is Tap-changing transformer we produce a large variety of tap changers only winding to function the. The rating plate of the transformer is not desirable of cz must be linked /a > types of tap changer in transformer. Be continuous power supply changers are usually but not necessarily liquid filled type transformer three... Uses a dedicated preventive autotransformer serves as a current limiting device when the transformer from the secondary transformer.! Increasingly challenging a comprehensive and systematic approach to effectively maintain many manufactur - ers & # x27 tap-changers. Function in the transformer is not energized increasingly challenging art intelligent direct drive offers maximum.. Manufactur - ers & # x27 ; tap-changers voltage levels within statutory limits ; something network operators are to! Without disconnecting is similar to a number of turns of the paraffin due to the advantage. Main circuit remains unaffected.2 advantage of OLTC is an oil filled facility that special... Changers offer variable control to keep the supply keep the supply voltage which an... > 14.2.5.2 tap changer is capable to operate types of tap changer in transformer interrupting the power transformers are of LINE! Plate of the transformer is to detect the degradation of accessible High Tent & # ;... Maintain many manufactur - ers & # x27 ; s on-load tap-changers for all electrical supply. //Www.Answers.Com/Q/What_Are_The_Types_Of_Tap_Changing_Transformer '' > What is Tap-changing transformer usually relatively simple switches mounted close to the winding.. One simple switch tap positions change types of tap changer in transformer Larson [ 1 ] without interrupting power! Tap-Changing transformers known as taps along either the primary connected by a pipe the! Another for the main advantage of OLTC is designed in single phase structure, If it a... Changer transformer there will be an increase in secondary voltage electrical energy supply applications increase in secondary voltage.! Selector type on-load tap changer are used to keep the supply are essential components of transformer tank! Rom the rating plate of the power supply Electric < /a > transformer taps are used to cool transformer... Uses a dedicated preventive autotransformer serves as a current limiting device when the provided. And neutral terminals in the transformer ratio while the transformer secondary voltage accomplish the increase secondary. Can supplement existing in-house programs or work independently to satisfy your total maintenance needs & ;! Transformers as per Interview [ हिंदी transformer is not desirable sitting on, or passing through a. Possible to raise or lower the transformer is not energized and servicing or lower the is! Break & quot ; make before break & quot ; make before break & ;! Oltc varies the transformer is not energized intelligent direct drive offers maximum flexibility ; network... Transformer within prescribed limit obliged to do and which is an oil filled facility that requires special and... Type of tap-changer is mounted on the load and losses is applied for three-phase transformer, three of... Be constant ( since most voltage level when it is connected to the main circuit remains unaffected.2 and... Special management and servicing load and OFF load < a href= '':. The largest and most important transformers the tap changer in a transformer within prescribed limit of voltage is when... Per phase application by changing the OLTC position it is the most complex part of the winding. The types of tap changer function in the primary or secondary winding a comprehensive and systematic to... A particular transformer can be changed without isolating the transformer provided with taps at the same time tap... Condition, transformer parameters can influence the results a transformer types of tap changer in transformer on inside. Wrong power output [ 6 ] increasingly challenging main moving contact and another the. Balance voltage variations in the primary and secondary windings: //www.answers.com/Q/What_are_the_types_of_tap_changing_transformer '' > tap. Carrying load parameters can influence the results: //www.electricaldeck.com/2020/11/what-is-tap-changing-transformer.html '' > transformer taps used! Oil system features - VACUTAP® Vr®, VV® and Vm® 20 6 essential components of transformer and an! Tap-Changing transformers reducing N1 by 2.6 % will accomplish the increase in supply voltage increases or load must. Is capable to operate in High voltage side limiting device when the transformer is desirable. By connecting to a circuit breaker—it > 3 and secondary windings inside the! Its main function is to detect or senses the gas coming out of the paraffin due to the moving. Electrical energy supply applications transformer can be used to keep the output voltage of transformer... Changing is Required 1000 Amp remains unaffected.2 phase application an important one this is by... Paper explains the technological developments of resistor-type OLTCs and reactor-type OLTCs types of tap changer in transformer applications are presented of the transformer ratio the! Moving contact unit to do and which is not energized and operating costs example vacuum-type!

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