Different types of electrical transformers are made for different purposes. Despite their design differences, different types use the same basic principles as those discovered in 1831 by Michael Faraday, and share some of the major functional parts.
Video Transformer types
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Laminated core
This is the most common type of transformer, which is widely used in electric power transmission and equipment to convert power to low voltage to power electronic devices. They are available in power ratings ranging from mW to MW. Insulated laminates minimize eddy current losses in iron core.
Small appliances and electronic transformers can use split coils, providing a high insulation level between rolls. The rectangular core consists of a stamp, often in the shape of an E-I form, but other forms are sometimes used. Shields between primary and secondary can be mounted to reduce EMI (electromagnetic interference), or screen scrolls are sometimes used.
Small appliances and electronic transformers may have a thermal cut-out attached to the winding, to turn off the power at high temperatures to prevent further heating.
Toroidal
Donoidal donut-shaped transformers save space compared to the E-I core, and can reduce the external magnetic field. It uses a ring-shaped core, a round copper coil wrapped in this ring (and thus threaded through the ring during winding), and tape for insulation.
The toroidal transformer has a lower outer magnetic field compared to a rectangular transformer, and may be smaller for a given power rating. However, the price is more expensive, because winding requires more complex and slower equipment.
They can be fitted with bolts through the center, using a washing machine and a rubber pad or with a pot in the resin.
Autotransformer
An autotransformer has one winding that is tapped at some point along the turns. Voltage is applied across the turns, and higher (or lower) voltages are generated in other parts of the same windings. The equivalent autotransfomer power rating is lower than the actual load power value. This is calculated by: load VAÃ, ÃÆ' â € "Ã, (| VinÃ, -Ã, Vout |)/Vin. For example, an automatic transformer that adjusts a 1000 VA load measured at 120 Volts until a 240 Volt supply has an equivalent rating of at least: 1,000VA (240V - 120V) Ã, Â ± 240VÃ, = Ã, 500VA. However, the actual rating (shown on the calculation plate) should be at least 1000 VA.
For voltage ratios not exceeding 3: 1, autotransformer is cheaper, lighter, smaller, and more efficient than a two-winded (two-winding) isolation transformer with the same rating. A large three-phase autotransformer is used in power distribution systems, for example, to connect 33 kV and 66 kV sub-transmission networks.
Variable autotransformer
By exposing parts of the winding windings of the autotransformer, and making a secondary connection through a sliding carbon brush, an autotransformer with a variable ratio of near-continuous variables can be obtained, allowing for the adjustment of the width voltage in a very small increase.
Inductor control
An induction regulator is similar in design to a wound-induced motor induction but is essentially a transformer whose output voltage varies by rotating relative secondary to primary - that is, rotating the rotor angle position. It can be seen as a power transformer that utilizes a rotating magnetic field. The main advantage of the induction regulator is that unlike variac, they are practical for transformers over 5 kVA. Therefore, such regulators find widespread use in high-voltage labs.
Transformer polyphase
For polyphase systems, multiple single-phase transformers can be used, or all phases can be connected to a single polyphase transformer. For a three phase transformer, three primary windings are connected together and three secondary windings are connected together. Examples of connections are wye-delta, delta-wye, delta-delta and wye-wye. A vector group shows the configuration of the windings and the phase difference between them. If the winding is grounded, the earth connection point is usually the center point of the wye winding. If the secondary is a delta reel, the ground can be connected to a tap center on one winding (high leg delta) or one phase can be earthed (the delta ground angle). The special purpose polyphase transformer is a zigzag transformer. There are many possible configurations that may involve more or less than six rolls and various tap connections.
Ground Transformer
Grounding or grounding transformers let three wires (deltas) supply the polyphase system to accommodate phase to neutral load by providing a return path for current to neutral. The most common Grounding Transformer incorporates a single winding transformer with a zig-zag winding configuration but can also be made with an isolated wye-delta winding transformer connection.
Phase-transfer transformer
This is a special type of transformer that can be configured to adjust the phase relationship between input and output. This allows the power flow in the controlled power grid, eg. to direct the power flow away from the shorter (but overloaded) connection to a longer path with excess capacity.
Variable-frequency transformer
A variable-frequency transformer is a special three phase power transformer that allows the phase relationship between the input and output coils to be continuously adjusted by rotating one-half. They are used to connect power lines with the same nominal frequency but without synchronous phase coordination.
Leaky or strayed field transformation
A leaked transformer, also called a stray-field transformer, has a significantly higher leakage inductance than other transformers, sometimes increased by magnetic bypass or shunt in essence between primary and secondary, which can sometimes be adapted to a set of screws. It provides a transformer with inherent current constraints due to loose coupling between the primary and secondary windings. In this case, the actual short-circuit inductance acts as a current limiting parameter. The output and input currents are low enough to prevent thermal overload under all load conditions - even if the secondary is shorted.
Usage
Leakage transformers are used for arc welding and high voltage discharge lamps (fluorescent lamps and cold cathode fluorescent lamps, which are connected series up to 7.5 kV AC). Acting later both are voltage transformers and as magnetic ballasts.
Another application is a low-voltage extra-low-voltage transformer for toys or bell installations.
Resonant transformer
A resonance transformer is a transformer in which one or both windings have a transverse capacitor and functions as a tuned circuit. Used on a radio frequency, a resonant transformer can function as a high-bandpass filter Q factor. The transformer winding has an air or ferrite core and the bandwidth can be adjusted by varying the coupling (mutual inductance). One common form is the IF transformer (intermediate frequency), which is used in superheterodyne radio receivers. They are also used in radio transmitters.
Resonant transformers are also used in electronic ballasts for gas discharge lamps, and high voltage power supplies. They are also used in some types of switching power supplies. Here the value of the short-circuit inductance is an important parameter that determines the resonant frequency of the resonant transformer. Often only the secondary winding has a resonant capacitor (or stray capacitance) and acts as a serial resonant tank circuit. When the short-run inductance of the secondary side of the transformer is L sc and the resonant capacitor (or stray capacitance) of the secondary side is C r , Resonance frequency? s of 1 'is as follows
The transformer is driven by a pulse or square wave for efficiency, generated by an electronic oscillator circuit. Each pulse serves to drive the sinusoidal oscillation resonance in winding coils, and because high voltage resonance can be developed in the secondary.
Application:
- Intermediate frequency (IF) transformer in a superheterodyne radio receiver
- Transformer tank in radio transmitter
- Tesla coil
- CCFL inverter
- Oudin coil (or Oudin resonator, named after its discoverer Paul Oudin)
- D'Arsonval Tools
- Ignition coil or induction coil used in ignition system of gasoline engine
- Electrical failure and insulation testing of equipment and high voltage cables. In the latter case, the secondary transformer is aligned with the cable capacitance.
Voltage transformer constant
By adjusting certain magnetic properties of the transformer core, and installing ferro-resonance tank circuits (additional capacitors and windings), the transformer can be adjusted to automatically keep the secondary winding voltage relatively constant for the main supply without additional circuit or manual. Settings. The ferro-resonance transformer runs hotter than standard power transformers, because the regulating action depends on core saturation, which reduces efficiency. The output waveform is highly distorted unless careful action is taken to prevent this. The saturating transformer provides a simple rough method to stabilize the AC power supply.
ferrite core
Ferrite core power transformers are widely used in mode-switched power supplies (SMPS). The powder core allows high-frequency operation, and hence a much smaller power-to-power ratio than an iron-laminate transformer.
The ferrite transformer is not used as a power transformer at the primary frequency because the iron core of the laminate is less than the equivalent ferrite core.
Planar Transformer
Manufacturers carve spiral patterns on printed circuit boards to form "coils" of planar transformers , replacing the wire windings used to create other types. Some planar transformers are commercially sold as discrete components. The other planar transformers are one of the many components on a printed circuit board. Planar transformers can be thinner than other transformers, which are useful for low-profile applications or when some printed circuit boards are stacked. Almost all planar transformers use planar ferrite core.
Oil cooled transformer
Large transformers used in power distribution or electrical substations have their cores and coils submerged in oil, which cool and isolate. Oil circulates through channels in the coil and around the coils and core assemblies, driven by convection. The oil is cooled by the outside of the tank in small ranks, and by air-cooled radiators in a larger rank. If a higher rating is required, or where the transformer is in the building or underground, the oil pump will circulate the oil, and the oil heat exchanger into the water can also be used. Some transformers may contain PCBs where or when their use is allowed. For example, until 1979 in South Africa. flame-retardant liquids such as silicone oil are now used instead.
Cast resin tray
The resin-resin power transformer wraps the coil in an epoxy resin. This transformer simplifies installation because it is dry, without oil cooler, so it does not require a fireproof safe for indoor installation. Epoxy protects the coils from dust and corrosive atmosphere. However, since the mold for roll casting is only available in fixed size, the transformer design is less flexible, which can make it more expensive if special features (voltage, rotation ratio, tapping) are required.
Isolating transformer
The isolation transformer connects two circuits magnetically, but does not provide a metallic conductive path between circuits. Examples of applications will be in the power supply for medical equipment, when necessary to prevent leakage from the AC power system to the device connected to the patient. Special purpose insulation transformers may include shielding to prevent electromagnetic noise coupling between circuits, or perhaps amplified insulation to withstand thousands of volts of potential difference between primary and secondary circuits.
Maps Transformer types
Transformer instrument
Instrument transformers are typically used to operate instruments from high voltage conduits or high current circuits, measuring and controlling secure insulation circuits from high voltage or current. The main winding of the transformer is connected to a high voltage or high current circuit, and a meter or relay connected to a secondary circuit. The instrument transformer can also be used as an isolation transformer so that a secondary quantity can be used without affecting the primary circuit.
Terminal identification (either alphanumeric like H 1 , X 1 , Y 1 , etc. Or the colored dots or dots impressed in this case) one end of each winding, shows the same instantaneous polarity and phase between the scrolls. This applies to both types of instrument transformers. The correct identification of terminals and cables is essential for proper operation of metering and protective relay instrumentation.
Current transformer
A current transformer (CT) is a series connected measuring device designed to provide the current in the secondary coil proportional to the current flowing in its primer. Current transformers are commonly used in metering and protective relays in the electric power industry.
Current transformers are often made by passing a single primary loop (either isolated cable or uninsulated bus bus) through an isolated toroidal core wrapped with multiple winding wires. CT is usually described by the ratio of the current from primary to secondary. For example, CT 1000: 1 provides an output current of 1 ampere when 1000 amperes flow through the primary winding. The current standard secondary rating is 5 amperes or 1 ampere, compatible with standard gauges. Secondary windings can be either a single ratio or have multiple tap points to provide various ratios. Care must be taken to ensure uninterrupted secondary winding of low impedance loads when current flows in the primer, as this may produce dangerous high voltage on the open secondary and may permanently affect the accuracy of the transformer.
Special constructed wideband CTs are also used, usually with an oscilloscope, to measure high-frequency waveforms or pulsed currents in a pulsed power system. One type provides an output voltage that is proportional to the measured current. Others, called Rogowski coils, require an external integrator to provide a proportional output.
The flow clamp uses a current transformer with a separate core which can easily coil the conductor in the circuit. This is a common method used in portable current measuring devices but a permanent installation using a more economical type of current transformer.
Voltage transformer or potential transformer
Voltage transformer (VT), also called a potential transformer (PT), is a type of parallel-connected instrument transformer, used for metering and protection in high-voltage circuits or phasor phase shift isolation. They are designed to present a negligible load on the measured inventory and have an accurate voltage ratio to enable accurate measurements. The potential transformer may have several secondary windings on the same core as the primary winding, for use in different gauges or protection circuits. The main one can connect phase to ground or phase to phase. The secondary ones are usually earthed on one terminal.
There are three main types of voltage transformers (VT): electromagnetic, capacitor, and optical. The electromagnetic voltage transformer is a wire-wound transformer. Voltage voltage transformers use potential divider capacitance and are used at higher voltages due to lower cost than electromagnetic VT. Optical voltage transformers exploit the electrical properties of optical materials. High voltage measurements are made possible by potential transformers.
Composite instrument transformer
A combined instrument transformer encloses a current transformer and a voltage transformer on the same transformer. There are two main combinations of current and voltage transformer designs: isolated oil papers and isolated SF 6 . One advantage of implementing this solution is to reduce traces of substations, due to the reduced number of transformers in a bay, supporting structures and connections as well as lower costs for civil works, transportation and installation.
Transformer pulse
A pulse transformer is a transformer that is optimized for rectangular pulse transmission (ie, pulses with fast rise and fall times and relatively constant amplitude). Small versions called signal types are used in digital logic and telecom circuits, often for matching logic drivers to transmission lines. Medium-sized power versions are used in power control circuits such as camera flash controllers. Larger power versions are used in the power distribution industry to connect low-voltage control circuits to high-voltage semiconductor power gates. Special high-voltage pulse transformers are also used to generate high-power pulses for radar, particle accelerators, or other high-energy pulsed power applications.
To minimize the pulse shape distortion, the pulse transformer must have a low value leak inductance and a distributed capacitance, and a high open-circuit inductance. In power type pulse transformers, low coupling capacitance (between primary and secondary) is important to protect the circuit on the primary side of the high-powered transients created by the load. For the same reason, high insulation resistance and high breakdown are required. A good transient response is required to maintain a rectangular pulse shape on the secondary, since a slow-angled pulse will create a switching loss in the power semiconductor.
The product of peak pulse voltage and pulse duration (or more accurately, voltage-time integral) are often used to characterize pulse transformers. In general, the greater this product, the larger and more expensive the transformer.
A pulse transformer with a definition has a duty cycle of less than 0.5; any energy stored in the coil during the pulse should be "discarded" before the pulse is fired again.
RF Transformer
There are several types of transformers used in radio frequency (RF) work. Laminated steel is not suitable for RF.
Air-core Transformer
This is used for high frequency work. Lack of nuclei means very low inductance. All currents generate current and induce a secondary voltage which is proportional to the mutual inductance. Such a transformer may be no more than a few rounds of wire soldered onto a printed circuit board.
Transformer ferrite core
Ferrite core transformers are widely used in impedance matching transformers for RF, especially for balun (see below) for TV and radio antennas. Many have only one or two rounds.
Transformer-line transformer
For radio frequency usage, the transformer is sometimes made of transmission line configuration, sometimes bifilar or coaxial cable, wound around ferrite or other type of core. This transformer style provides very wide bandwidth but only a limited number of ratios (such as 1: 9, 1: 4 or 1: 2) can be achieved with this technique.
The core material increases the inductance dramatically, increasing its Q factor. The core of the transformer helps improve performance at the lower end of the band frequency. RF transformers sometimes use a third coil (called tickler winding) to inject the feed into the previous stage (detector) in the antique regenerative radio receiver.
In RF and microwave systems, a quarter wave impedance transformer provides a way of matching the impedance between circuits over a limited frequency range, using only the length of the transmission line. The line may be coaxial cable, waveguide, stripline or microstripline.
Balun
Balun is a specially designed transformer to connect between balanced circuits (not grounded) and unbalanced (grounded). These are sometimes made of transmission line configurations and sometimes bifilar or coaxial cables and are similar to transmission line transformers in their construction and operation. Balun can be designed to not only interface between balanced and unbalanced loads, but also provide impedance matching between types of load.
IF transformer
The ferrite core transformer is widely used in the (intermediate frequency) (IF) stage of the superheterodyne radio receiver. They are mostly tuned tuners, containing threaded ferrite slugs that are screwed in or out to adjust the IF tuning. Transformers are usually canned (protected) for stability and reduce interference.
Audio Transformer
The audio transformer is specially designed for use in audio circuits to carry audio signals. They can be used to block radio frequency interference or DC components from audio signals, to split or combine audio signals, or to provide impedance matching between high impedance and low impedance circuits, such as between high impedance valve amplifier and low impedance loudspeaker outputs, or between the high impedance instrument output and the low impedance input of the mixing console. The audio transformers that operate with the loudspeaker voltage and current are larger than those that operate on a microphone or channel level, which carry much less power. Bridge transformers connect 2-wire and 4-wire communication circuits.
Being a magnetic device, an audio transformer is susceptible to an external magnetic field as generated by an AC current carrying conductor. "Hum" is a term commonly used to describe unwanted signals originating from a "primary" power supply (typically 50 or 60 Hz). Audio transformers used for low-level signals, such as those from microphones, often include magnetic shields to protect external magnetic signals.
Audio transformers were originally designed to connect different phone systems to each other while keeping their respective power supplies isolated, and still often used to connect professional audio systems or system components, to eliminate hum and hum. Such transformers typically have a 1: 1 ratio between primary and secondary. It can also be used to separate signals, balance an unbalanced signal, or give a balanced signal to unbalanced equipment. Transformers are also used in DI boxes to convert high impedance instrument signals (eg, bass guitar) to low impedance signals to enable them to connect to microphone inputs on the mixing console.
A very important component is the output transformer of the valve amplifier. The valve circuit for quality reproduction has long been produced without any other (inter-stage) audio transformer, but an output transformer is required to pair a relatively high impedance (up to several hundred ohms depending on configuration) from the output valve (s) to the low impedance of the loudspeaker. (Valves can provide low current at high voltage; speakers require high currents at low voltage.) Most solid-state power amplifiers do not require an output transformer at all.
Audio transformers affect the sound quality because they are not linear. The harmonic distortion is added to the original signal, especially the odd-order harmonics with emphasis on third-order harmonics. When the incoming signal amplitude is very low, there is not enough level to energize the magnetic core (see coercivity and magnetic hysteresis). When the amplitude of the incoming signal is very high the transformer is saturated and adds harmonic ringing. Other non-linearity comes from limited frequency response. For a good low-frequency response a relatively large magnetic core is required; High power handling increases the required core size. A good high-frequency response requires carefully designed and implemented windings without excessive inductance leakage or stray capacitance. All this makes the component expensive.
Early amplifiers of audio power transistors often have an output transformer, but they are eliminated as advances in semiconductors allow design of amplifiers with low enough output impedance to drive the loudspeaker directly.
Transformer loudspeaker
In the same way that the transformer creates a high voltage power transmission circuit that minimizes transmission losses, the loudspeaker transformer can power many individual loudspeakers from a single audio circuit operated at a normal higher than normal normal loudspeaker voltage. This app is common in public address apps. Such circuits are usually referred to as constant voltage amplifier systems. Such a system is also known as the nominal voltage of the loudspeaker, such as 25 - , 70 - and 100-volt speaker system (voltage corresponding to the power rating of speakers or amplifiers). The transformer increases the output from the system amplifer to the distribution voltage. In a remote loudspeaker location, the step-down transformer corresponds to the loudspeaker to the line recognition voltage, so that the speaker produces a nominal output value when the channel is at nominal voltage. Loudspeaker transformers typically have several main taps to adjust the volume on each speaker in stages.
Output transformer
The valve amplifier (tube) almost always uses an output transformer to match the high load impedance requirements of the valves (several kilohms) to the low impedance speakers
Small signal transformer
Moving the coil phonograph cartridge produces a very small voltage. In order for this to be amplified by a reasonable noise-signal ratio, it usually requires a transformer to convert the voltage to a more general range of moving magnetic cartridges.
Microphones can also be matched with their loads with a small, mumetally protected transformer to minimize voting. This transformer is less widely used today, because the distorted buffer is now cheaper.
Interstage and clutch transformer
In a push-pull amplifier, an inverse signal is needed and can be obtained from a transformer with a central tapped winding, used to drive two active devices in the opposite phase. This phase division transformer is not widely used today.
Other types
Transactor
Transactor is a combination of transformer and reactor. The transactor has an iron core with an air gap, which limits the coupling between reels.
Hedgehog
Hedgehog transformers are sometimes found on homemade 1920s radios. They are a homemade audio interstage clutch transformer.
The round copper wire surrounds the middle half of the length of an insulated iron wire bundle (eg a floris wire), to make the reels. The ends of the iron wire are then bent around the electric windings to complete the magnetic circuit, and the whole is wrapped with a ribbon or rope to hold it together.
Variometer and variocoupler
Variometer is a type of RF-AC inductor with two windings. One common form consists of a coil wound on a short hollow cylinder shape, with a second smaller coil inside, mounted on the shaft so that its magnetic axis can be rotated against the outer coil. Both coils are connected in series. When both coils are collinear, with their magnetic field pointing in the same direction, two magnetic fields add, and the inductance is maximum. If the inner coil is rotated so that the axis at the outer coil angle, the magnetic field does not increase and the inductance is less. If the inner coil is rotated to become collinear with the outer coil but the magnetic field is pointing in the opposite direction, the planes cancel each other out and the inductance is very small or zero. The advantage of the variometer is that the inductance can be adjusted continuously, over a wide range. Variometers are widely used in radio receivers of the 1920s. One of their main uses today is as antenna coil matching to match long wave radio transmitters to their antenna.
The vario-coupler is a device with similar construction, but the two coils are not connected but attached to a separate circuit. So it functions as an air-core RF transformer with variable clutch. The inner coil can be rotated from an angle of 0 ° to 90 ° with its exterior, reducing the mutual inductance from maximum to near zero.
The pancake coil variometer is another common construction used on receivers and transmitters of the 1920s. It consists of two flat spiral coils that are hung vertically facing each other, hinged on one side so that one can swing away from the other to a 90 ° angle to reduce the clutch. The flat spiral design serves to reduce the capacitance and parasitic losses in radio frequency.
Pancakes or "honeycomb" coil vario-couplers were used in the 1920s in general Armstrong or "reminder" regenerative radio receivers. One coil is connected to the detector tube box circuit. Other coils, coil "tickler" connected to the circuit plate (output) tube. It feeds back some of the signals from the plate circuitry to the input again, and this positive feedback increases the gain and selectivity of the tube.
Transformer play
Rotator is a special transformer that combines electrical signals between two rotating parts of each other - alternatively for the slip ring, which is susceptible to wear and contact noise. They are commonly used in helical tape magnetic tape applications.
Variable differential transformer
The variable differential transformer is a rough non-contact position sensor. It has two phased preliminaries that nominally produce zero output in the secondary, but each core movement changes the coupling to produce a signal.
Resolver and synchro
The two-phase resolver and the associated three-phase synchronization are rotary position sensors that work above 360 ​​Â ° full. Primers are rotated in two or three seconds at different angles, and secondary signal amplitude can be translated into corners. Unlike variable differential transformers, coils, and not just cores, move relative to each other, so a slip ring is required to connect the main ones.
Resolvers produce in-phase and quadrature components that are useful for computing. Synchros produces a three-phase signal that can be connected to other synchros to play it in a generator/motor configuration.
See also
- Three phases
- Three phase electric power
- Buck-boost Transformer
- Tap the modifier
- Transformer
- Generator-motor
References
Source of the article : Wikipedia
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