1 edition of Determination of current ratio and phase angle of current transformers found in the catalog.
Determination of current ratio and phase angle of current transformers
Abraham S. Benjamin
Written in English
|Statement||by Abraham S. Benjamin and Harold E. Smith|
|Contributions||Smith, Harold E.|
|The Physical Object|
|Pagination||iii, 48 leaves :|
|Number of Pages||48|
Typically, devices with mA output are called "current sensors," as opposed to current transformers. Note: CT ratios express the current rating of the CT, not merely the ratio of the primary to the secondary currents. For example, a /5 CT would not fulfill the function of a 20/1 or a 10/ CT. Instrument Transformer. Instrument transformers means current transformer & voltage transformer are used in electrical power system for stepping down currents and voltages of the system for metering and protection purpose. Actually relays and meters used for protection and metering, are not designed for high currents and voltages.
The main cause of the ratio and phase angle errors of a current transformer is the exciting current I o. In an ideal TC, in which exciting current does not exist, I 1 and – (n 2 /n 1) I 2 presented in Figure 2, are coincident. Thus, the primary current value, obtained from the secondary current, would be equal to the absolute value of the. An analysis of the available null methods indicates that difficulties are encountered with the accurate determination of the ratio and phase angle errors of potential transformers in which voltages in excess of 30 KY are involved. The use of a high voltage condenser with a negli- gible loss angle has become universal.
ference is important for current transformers because leakage flux in the core affects current ratio. It also improves the per-formance of current transformers and subjects their perform-ance to simple calculation. Voltage transformers are designed so the through impedance (RS,R,XP, and X) is as low as possible, while current transform-. • To determine the turns ratio of a single phase transformer. Introduction From Figure the turn’s ratio of a single phase transformer is defined as the ratio of the primary winding voltage V1 to the secondary winding voltage V2 when no load is applied as follow 1 2 a P S VV VV == () v p +-N p s +-v p The current angle is thus.
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Definition of Instrument Transformer. Instrument transformers means current transformer & voltage transformer are used in electrical power system for stepping down currents and voltages of the system for metering and protection purpose.
Actually relays and meters used for protection and metering, are not designed for high currents and voltages. A current transformer (CT) is an instrument transformer in which the secondary current is substantially proportional to primary current and differs in phase from it by ideally zero degree.
CT Accuracy Class or Current Transformer Class. A current transformer is similar to a electrical power transformer to some extent, but there are some difference in construction and operation principle.
Thesis (B.S.)--Armour Institute of Technology, Determination of current ratio and phase angle of current transformers Item PreviewPages: A current transformer is an instrument transformer, used along with measuring or protective devices, in which the secondary current is proportional to the primary current (under normal conditions of operation) and differs from it by an angle that is approximately zero.
Current transformers. Definition of Current Transformer(CT) A CT is an instrument transformer wherein the secondary current is considered proportional to primary cutting-edge and differs in a segment from it through ideally 0 degrees. CT Accuracy Class or Current Transformer Class.
Ratio of Current Transformer(C.T.) ormation Ratio: it is the ratio of the magnitude of primary current phasor to the secondary current phasor. Nominal Ratio: Determine the phase angle and ratio errors for the rated burden and rated secondary current at pf lagging and pf leading.
Neglect the resistance and leakage. In an ideal current transformer, primary to secondary current ratio is exactly equal to the secondary to primary turns ratio and also currents in each winding produce equal mmf in exact anti-phase. However, in actual practice the current ratio diverges from turns ratio and also certain phase angle exist in between them from the opposition.
Assuming an ideal transformer and the phase angles: Φ P ≡ Φ S. Note that the order of the numbers when expressing a transformers turns ratio value is very important as the turns ratio expresses a very different transformer relationship and output voltage than one in which the turns ratio is given as: Transformer Basics Example No1.
Current Transformer White Paper The Basics of Current Transformers Ratio The CT ratio is the ratio of primary current input to secondary current output at full load. For example, a CT with a ratio of is rated for primary amps at full load and will produce 5 amps of secondary current when amps flow through the primary.
The phase angle error, on the other hand, cannot be corrected, being a function of the reactive component of the excitation characteristics which vary widely over the current range and must take priority in the design of the transformer and choice of core.
current, Ira, essentially subtracts from the metered current and effects the true ratio and phase angle of the output current.
The simplified equivalent circuit of a current transformer, as shown in Figurerepresents the important elements of a current transformer, where the ratio of primary to secondary turns is: N «=—K [turnsratio.
Current transformers Principle of operation of CT. A current transformer is defined as “as an instrument transformer in which the secondary current is substantially proportional to the primary current (under normal conditions of operation) and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections.”.
The current transformer has two errors – ratio error and a phase angle error. Current Ratio Errors – The current transformer is mainly due to the energy component of excitation current and is given as Where I p is the primary current.
K t is the turn ratio and is the secondary current. For subtractive polarity the voltage waveforms across H1 H2 and X1 X2 has same phase angle. In other words the potential of H1 and X1 rise and fall in unison. For additive polarity the voltage waveforms across H1 H2 and X1 X2 has phase angle difference of degree.
Additional reading: Phase Sequence and Phase Angle. Current Transformer Saturation. A current transformer (CT) is a type of transformer that is used to reduce or multiply an alternating current (AC).
It produces a current in its secondary which is proportional to the current in its primary. Current transformers, along with voltage or potential transformers, are instrument ment transformers scale the large values of voltage or current to small.
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Free shipping for many products. I 1 = primary current, I 2 = secondary current. Example: A 50 kVA single-phase transformer has a V primary, and a V secondary.
Assuming an ideal transformer, determine (a) the primary and secondary full-load currents, (b) the transformer turns ratio. a) V 1 = V, V 2 = V, Transformer Rating = 50 kVA = V 1 × I 1 = V 2 × I 2. For example, If the rating of a three-phase V rated induction motor is A, then, according to the NEC handbook, we would select a current transformer with a A ratio.
IMPORTANT – remember to verify the outside diameter of your conductor is less than the inside diameter of the current transformer. 5 amperes as the secondary rating of current transformers.
The ratio of an instrument transformer is the relationship of its primary rating to its secondary rating. For example, the potential transformer mentioned above having a rating of volts will have a ratio of and the current transformer having a rating of.
The method of comparing the vector couple voltages also allows measuring the angle (phase slip) between vectors at the same time. Determining the Connection Group. Depending on the type of the transformer, the input and output windings of a multi-phase transformer are connected either as star (Y) or delta (D) or zigzag (Z).The phase angle between the high voltage and the low.
The single phase secondary injection unit PTEC can also be used for current transformer testing; thanks to the voltage injection capacity of the PTEC and its integrated measuring functions, it is possible to verify, in manual method, the knee point in a current transformer, provided this is under V; at any case, any of the primary.
It is possible to test single phase two-winding transformers with a three-phase TTR test set by only utilizing the H1, H2 and X1, X2 leads. Transformer Turns Ratio Test Values Turns ratio test results should not deviate by more than one-half percent from either the adjacent coils or the calculated ratio, test values outside of this tolerance.These include current transformers with ratios of A/5 A and higher, with ratio errors of less than 5 in both magnitude and phase with burdens up to Omega and at.