TRANSFORMERS - Washington University In St. Louis

2m ago
2.26 MB
41 Pages
Last View : 1m ago
Last Download : 1m ago
Upload by : Joao Adcock

2.B.IntroductionPhysics of Coupled NetworksMagnetic MaterialsA Network ApproachCore Loss and Jordan-type Loss CoefficientsThe Equivalent Circuit of a Real Transformer at Low FrequencySimple Open-circuit and Short-circuit TestsThree Phase TransformersAutotransformersPractical ConsiderationsStandard (ANSI C57.12.90-1973) Electrical TestsReferencesEXPERIMENT1.2.3.4.Equipment ListThe Single Phase Transformera. Winding resistancesb. Open circuit testc. Short circuit testMaximum Power Transfera. Maximum Power Transfer Circuitb. Load ResistanceReportTransformers -- 1

Transformers -- 2

Transformers -- 3

Transformers -- 4

Transformers -- 5

Transformers -- 6

Transformers -- 7

Transformers -- 8

quantity called the permeability of the medium is commonly defined as µ [ B H] ,(2.11)Hand clearly varies with field strength. Suppose next that the H-vector is reduced. It is generallyfound, as illustrated in Fig. 2.1, that the 'normal" or "virgin" curve (i.e., initial path) is notretraced but that instead the domains resist reorientation and a so-called hysteresis loop3 results(cf. Olsen, 1966; Watson, 1980); it must be emphasized that the hysteresis loop is not a unique entity but that as i H i is -swept slowly from 0 to some H and then back to some H and isthen cycled between H and H , a different loop is generated for each ordered pair (H ,H. ).Moreover, the qualitative shape of the hysteresis loop can and does vary greatly from onematerial to another, as the curves of Fig. 2.2 illustrate. Some few descriptive terms may beuseful:(α)A loop shaped like that of Fig. 2.1 is called "normal". If the loop is of small relative area(say BrHc (µ0Msat)Hσ), the material is said to be "soft";3The term hysteresis is derived from the Greek υατερησισ (a coming late or a delay) and can be traced back tothe work of J. A. Ewing in the 1880's (cf. Heck, 1974).Transformers -- 9

Transformers -- 10

Transformers -- 11

Transformers -- 12

Transformers -- 13

Transformers -- 14

Transformers -- 15

Transformers -- 16

Transformers -- 17

Transformers -- 18

Transformers -- 19

Transformers -- 20

Transformers -- 21

Transformers -- 22

Transformers -- 23

Transformers -- 24

7. EXPERIMENTAL TESTSOPEN CIRCUITThe equivalent network will be as shown in Fig. 2-6a.Usually we can neglect R1 and Xe for this case and havePOC RE{VLI*LOC} GC VL 2(2.32)ILOC (Gc jBm)VL(2.33)So, measurement of power input, line current, and line voltage to the transformer with secondaryopen-circuited will yield the network elements Gc and Bm . Additionally, the transformationratio, a k L1/L2 can be approximately obtained by measuring the voltage appearing across thesecondary.SHORT CIRCUITFigure 2-6b gives the equivalent network in this case. Sufficient accuracy can often beachieved by ignoring the shunt branch, Gc jBm in which case we havePSC ILSC 2R1 I2 2R2 ,(2.34)or, using the transformation ratio, a , we havePSC ILSC 2 [R1 a2R2] .(2.35)VL (R1 a2R2 jXe) ILSC ,(2.36)Additionally,so the quantities [R1 a2R2] and Xe can be inferred frommeasurements with the transformer secondary shorted. R1 and R2 can be separated by a DCohmmeter measurement of R1 .Transformers -- 25

Transformers -- 26

Transformers -- 27

Transformers -- 28

Transformers -- 29

Transformers -- 30

Transformers -- 31

Transformers -- 32

Transformers -- 33

Transformers -- 34

Transformers -- 35

Chapman, Stephen J. 2002. Electric Machinery and Power System Fundamentals. McGrawHill, New York, New YorkTransformers -- 36

B.EXPERIMENT1.Equipment Lista. The standard equipment normally found at each station.b. Various current shunts and probes.c. One single-phase wattmeter (YEW model 2041 or Extech model 382860).d. One variable autotransformer (Staco model 3PN1010).e. One single-phase Transformer Test Rig (Stancor model 8666).f . One rheostat module with two 50-Ω rheostats rated at 4.5 A eachg. One 200 Ohm, 20 Watt, resistor.h. Various power cords.2.The Single Phase-Transformera. Using a suitable method, accurately measure the DC resistances of theprimary and the secondary # . (NOTE: Consult the connection diagram forthe Transformer Test Rig.) Constraint: The current delivered to thewinding under test must not exceed 1 Amp.b. Connect the primary of the transformer to the autotransformer. Opencircuit the secondary. Use a Wattmeter to determine POC, the open circuitinput power. If “P” and “S” denote (respectively) primary and secondaryrms quantities, measure VP, IP, and VS over the VP interval [10,140] * . Beabsolutely certain to use a sensible voltage grid . And take care to usesuitable meter ranges throughout. Turn off the autotransformer whenfinished.c. Connect a shunt across the secondary and float the center tap. Caution:Start with very low autotransformer voltage and increase voltage slowly.#Those of you who are unfamiliar with the up-sides and down-sides of the two-wire and four-wire techniques maywish to study and meditate upon them before coming to lab. Note also that the instructors have perverselyneglected to tell you what frequency to use in these measurements. Be assured that you will need todiscuss these points in the write-up.*This is a POWER course, so we presumably mean volts. Sometimes one has to interpret instructions based upontheir context. I’ve always liked to take a minimalist approach to data dredging. But of course it would never do to have theplotted points too far apart, especially since this might make difficult (impossible?) an accuratedetermination of the transformer’s parameters.Transformers -- 37

Transformers -- 38

Use the Wattmeter to measure PSC, the short circuit input power. Measurealso IP, VP, and IS over the IS interval [1,12]. Be certain to space yourcurrent readings sensibly and to employ sensible meter ranges.d. Parts b. and c. above provide sufficient information to determine anequivalent circuit for the single-phase transformer. To obtain comparisondata, connect the rheostats as a secondary load with 9 Amp capability andset the input voltage to rated voltage of 120 Vrms. Holding the inputvoltage at its rated value, adjust the rheostats and make measurements ofPP, VP, IP, VS, and IS for load currents IS of 1, 3, 5, 7, and 9 A.3.Maximum Power Transfera. Construct a power source consisting of the autotransformer and a series200 Ohm, 20 Watt, resistor. Connect the primary of the single-phasetransformer in the Transformer Test Rig to this power source. Construct avariable load using a single rheostat connected to the secondary of thesingle-phase transformer and set the load to maximum resistance.Instrument the set-up so that you can measure the voltage and powerdelivered by the autotransformer and the voltage and current in thevariable load.b. Set and maintain the autotransformer voltage to 100 Vrms. Adjust the loadresistance until maximum power is being dissipated by the load andrecord all measurements. Be careful not to exceed the 4.5 Amp rating ofthe rheostat.Transformers -- 39

4.REPORTa. In Part 2.a, what were measured DC Rprimary and Rsecondary? Include theraw data as well as the derived resistances. Also, explain the resistancemeasuring technique you employed; and justify your choice.b. All data measured in parts 2.b &2.c should be normalized relative tovalues measured at rated primary voltage or rated secondary current. Besure to include the raw data and the normalized data in tabular form. Plotthe normalized POC, IP, & Vs data from your open circuit test vs. primaryvoltage VP and plot normalized PSC & IP from your short circuit test vs.secondary current IS. Carefully explaining (step by step) your procedure,construct an equivalent circuit for the transformer that was tested. Showall calculations. Your equivalent circuit should contain and have numericalvalues for all the elements of the last diagram on Figure 2-5d on page 24.c. Using the equivalent circuit constructed in Part b. above, calculate andgenerate plots displaying % efficiency versus load R and % regulationversus the load R, where the values of R are those calculated from VSand Is measured in part 2.d. These quantities are defined as:Pload(R)% efficiency 100 P (R)input% regulation 100VS( ) VS(R).VS( )Also, calculate the efficiency and regulation for the data taken in part 2.d.Plot these data points on the corresponding plots calculated from theequivalent circuit that you determined for the transformer.d. What were the powers delivered by the autotransformer and dissipated bythe load when maximum power transfer was obtained? What was theoverall efficiency using this resistance matching approach? What was theresistance of the load when maximum power transfer occurred? Howdoes this value of resistance compare to the theoretical value?Transformers -- 40

Transformers -- 41

Transformers -- 25 7. EXPERIMENTAL TESTS OPEN CIRCUIT The equivalent network will be as shown in Fig. 2-6a. Usually we can neglect R1 and Xe for this case and have POC RE{VLI*LOC} GC VL 2 (2.32) ILOC (Gc jBm)VL (2.33) So, measurement of power input, line current, and line voltage to the transformer with secondary

Related Documents:

applications including generator step-up (GSU) transformers, substation step-down transformers, auto transformers, HVDC converter transformers, rectifier transformers, arc furnace transformers, railway traction transformers, shunt reactors, phase shifting transformers and r

7.8 Distribution transformers 707 7.9 Scott and Le Blanc connected transformers 729 7.10 Rectifier transformers 736 7.11 AC arc furnace transformers 739 7.12 Traction transformers 745 7.13 Generator neutral earthing transformers 750 7.14 Transformers for electrostatic precipitators 756 7.15 Series reactors 758 8 Transformer enquiries and .

2.5 MVA and a voltage up to 36 kV are referred to as distribution transformers; all transformers of higher ratings are classified as power transformers. 0.05-2.5 2.5-3000 .10-20 36 36-1500 36 Rated power Max. operating voltage [MVA] [kV] Oil distribution transformers GEAFOL-cast-resin transformers Power transformers 5/13- 5 .

- IEC 61558 – Dry Power Transformers 1.3. Construction This dry type transformer is normally produced according to standards mentioned above. Upon request transformers can be manufactured according to other standards (e.g. standards on ship transformers, isolation transformers for medical use and protection transformers.

cation and for the testing of the transformers. – IEC 61378-1 (ed. 2.0): 2011, converter transformers, Part 1, Transformers for industrial applications – IEC 60076 series for power transformers and IEC 60076-11 for dry-type transformers – IEEE Std, C57.18.10-1998, IEEE Standard Practices and Requirements for Semiconductor Power Rectifier

Transformers (Dry-Type). CSA C9-M1981: Dry-Type Transformers. CSA C22.2 No. 66: Specialty Transformers. CSA 802-94: Maximum Losses for Distribution, Power and Dry-Type Transformers. NEMA TP-2: Standard Test Method for Measuring the Energy Consumption of Distribution Transformers. NEMA TP-3 Catalogue Product Name UL Standard 1 UL/cUL File Number .

Instrument . Transformers. 731. 736 737. 735. g. Multilin. 729 Digital Energy. Instrument Transformers. 738 739. 739 Instrument Transformers. Control Power Transformers 5kV to 38kV - Indoor type. Current Transducers 600 Volt Class IEC - Rated Instrument Transformers

Ex. 8-2 Transformers in Parallel . 347 Connecting transformers in parallel to supply greater load power. Measuring the efficiency of parallel-connected transformers. Ex. 8-3 Distribution Transformers . 355 Introduction to basic characteristics of distribution transformers.

– dry-type transformers (IEC 60076-11); – converter transformers for industrial applications (IEC 61378-1). Add new subclause 1.3 Transformers excluded from scope Excluded from the scope of this specification are the following types of transformers:

IEC 60076-11 – Power transformers – Part. 11: Dry – type. IEC 60076-1 – Power transformers – Part. 1: General. IEC 60076-2 – Power transformers – Part. 2: Temperature rise. IEC 60076-3 – Power transformers – Part. 3: Insulation levels, dielectric test and external clearances in air.

Information concerning loadability of power transformers is given in IEC . ٦٠٣٥٤, for oil-immersed transformers, and IEC ٦٠٩٠٥, for dry-type transformers. Guidance for impulse testing of power transformers is given in IEC . ٦٠٧٢٢. ١٫ ٢

IEC 60616, Terminal and Tapping Markings for Power Transformers. IEC 60722, Guide to the Lightning Impulse and Switching Impulse Testing of Power Transformers and Reactors. IEC 60726, Dry-type Power Transformers. IEC 61378-1, Converter Transformers, Part 1: Transformers for Industrial Applications. 5.0 VFD PERFORMANCE REQUIREMENTS

These devices make up the majority of the loads supplied by the control circuit transformer. Control circuit transformers ar e also referred to as Industrial Control Transformers, Machine Tool Transformers, and Control Power Transformers. Inrush Volt-Ampere and Sealed Volt-Ampere Considerations . Mu

the Group develops and produces power transformers in the range from 50 kVA up to incl. 1,200 MVA within the voltage range up to 765 kV. The product line includes oil transformers, phase shifting transformers, cast-resin transformers, compact stations and shunt and series reactors. Wit

9.7.1 Current transformers according to IEC 61869-2, class P, PR 127 9.7.2 Current transformers according to IEC 61869-2 class PX, TPS 127 9.7.3 Current transformers according to ANSI/IEEE 128 10. Non Coventional Instrument Transformers 129 10.1 Fiber Optic Curren

IEC 60076-10 2001 Power transformers -- Part 10: Determination of sound levels EN 60076-10 2001 IEC 60076-11 2004 Power transformers -- Part 11: Dry-type transformers EN 60076-11 2004 IEC 60076-12 2008 Power transformers -- Part 12: Loading guide for dry-type power transformers - - IEC 60076

sensitive electronic appliances. Booster transformers are often used to improve old railway feeder systems. Description Booster transformers are single-phase transformers with the ratio 1:1. They have low impedance value

IEC 60076-1 Power transformers – Part 1: General IEC 60076-2 Power transformers – Part 2: Temperature rise IEC 60076-3 Power transformers – Part 3: Insulation levels, dielectric tests and external clearances in air IEC 60076-5 Power transformers – Part 5: Ability to withstand short circuit

SANS 60076-1 : Power Transformers Part 1: General SANS 60076-2 : Power Transformers Part 2: Temperature Rise SANS 60076-3 : Power Transformers Part 3: Insulation levels, dielectric tests and external clearances in air. SANS 60076-5 : Power Transformers Part 5: Ability to withstand short circuit International Standards IEC 60076 : Power transformers

tions of high-frequency transformers. The varied uses of under coupling, critical coupling, transitional coupling, and overcoup ling are dwelt upon. Gain-bandwidth factors, special transformers and their applications, saturable reactors, self-saturating saturable re actors, voltage-regulating transformers, and balancing transformers