Category: Definition. The voltage required to circulate the rated current under short-circuit conditions when connected on the rated voltage tap, is the impedance voltage. Rated current is circulated through the windings with the secondary short-circuited. The impedance voltage and load loss is measured.
What is per unit impedance?
Per-unit system. In the power systems analysis field of electrical engineering, a per-unit system is the expression of system quantities as fractions of a defined base unit quantity. A per-unit system provides units for power, voltage, current, impedance, and admittance.
What is fault level in electrical system?
From Wikipedia, the free encyclopedia. In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which current bypasses the normal load. An open-circuit fault occurs if a circuit is interrupted by some failure.
What is percentage impedance voltage?
Definition. The percentage impedance of a transformer is the volt drop on full load due to the winding resistance and leakage reactance expressed as a percentage of the rated voltage. It is also the percentage of the normal terminal voltage required to circulate full-load current under short circuit conditions.
Why is transformer impedance important?
“It is also the percentage of the normal terminal voltage at one side required to circulate full-load current under short circuit conditions on other side.” The impedance of a transformer has a major effect on system fault levels. It determines the maximum value of current that will flow under fault conditions.
What does mean short circuit impedance?
A basic electrical theorem says the amount of current that will flow through a short circuit depends on two variable values: The system voltage and the connected total impedance of the current flow path from the source to the point of the fault.
What is impedance of a circuit?
Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied. Impedance extends the concept of resistance to AC circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude.
What is meant by leakage reactance?
Leakage Reactance of Transformer. All the flux in transformer will not be able to link with both the primary and secondary windings. A small portion of flux will link either winding but not both. This portion of flux is called leakage flux. This self-reactance associated with resistance of transformer is impedance.
What is a leakage transformer?
Leakage Transformers are transformers where the magnetic flux of the secondary is loosely coupled to the flux of the primary. This loose coupling ensures that the transformer can withstand short circuit conditions.
What is fringing in a magnetic circuit?
The fringing effect results from the presence of the air gap in the magnetic circuit. The main consequence of the fringing effect is to make the magnetic flux density of the air gap different from the flux density of the core due to the path of the flux.
What is fringing effect in capacitor?
Fringing is the bending of the electric flux lines near the edge of the parallel plate capacitors. Fringing is also known as ” edge effect ”. Normally the flux lines inside the capacitor are uniform and parallel.
What is magnetic fringing?
Flux fringing is especially pertinent to magnetic cores with an air gap, for instance in flyback transformers or PFC inductors. The magnetic core is designed so that a well defined gap is placed in the magnetic circuit for storing energy in magnetic field.
What is flux in magnetic circuit?
A magnetic circuit is made up of one or more closed loop paths containing a magnetic flux. The flux is usually generated by permanent magnets or electromagnets and confined to the path by magnetic cores consisting of ferromagnetic materials like iron, although there may be air gaps or other materials in the path.
What is the magnetic shield?
Electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. Electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as RF shielding.
What materials can block radiation?
The high density of lead (11.34 grams per cm³) makes it a useful shield against X-ray and gamma-ray radiation. Lead, in its pure form, is brittle and cannot be worn as apparel. To transform pure lead into a wearable radiation shielding material it’s mixed with binders and additives to make a flexible lead vinyl sheet.
What materials block radio waves most effectively?
Thin amounts of plastic wrap, wax paper, cotton and rubber are not likely to interfere with radio waves. However, aluminum foil, and other electrically conductive metals such as copper, can reflect and absorb the radio waves and consequently interferes with their transmission.
What materials can block a WIFI signal and why?
Some material suggestions include:
Steel baking pans.
Glass baking pans.
Large container filled with water.
What material can resist radiation?
Beta particles (electrons) are more penetrating, but still can be absorbed by a few millimeters of aluminum. However, in cases where high energy beta particles are emitted shielding must be accomplished with low atomic weight materials, e.g. plastic, wood, water, or acrylic glass (Plexiglas, Lucite).
What kind of material blocks radiation?
Despite their ability to penetrate other materials, in general, neither gamma rays nor x-rays have the ability to make anything radioactive. Several feet of concrete or a few inches of dense material (such as lead) are able to block these types of radiation.
How do lead aprons stop radiation?
Because of lead’s density and large number of electrons, it is well suited to scattering x-rays and gamma-rays. These rays form photons, a type of boson, which impart energy onto electrons when they come into contact. When the radiation attempts to pass through lead, its electrons absorb and scatter the energy.
How thick does lead have to be to stop radiation?
γ GAMMA: To reduce typical gamma rays by a factor of a billion, thicknesses of shield need to be about 13.8 feet of water, about 6.6 feet of concrete, or about 1.3 feet of lead. Thick, dense shielding is necessary to protect against gamma rays. The higher the energy of the gamma ray, the thicker the shield must be.
How effective is a lead apron?
Lead aprons are the most effective personal radiation protection means and should be worn by everyone in a fluoroscopy room (except the patient). Lead aprons may reduce the dose received by over 90% (85%-99%) depending on the energy of the X-rays (kV setting) and the lead equivalent thickness of the apron.
What is the turns ratio of a transformer?
The ratio of the transformers primary and secondary windings with respect to each other produces either a step-up voltage transformer or a step-down voltage transformer with the ratio between the number of primary turns to the number of secondary turns being called the “turns ratio” or “transformer ratio”.