Air Core Transformer. A transformer that uses air to separate the primary and secondary windings. A transformer composed of two or more coils that are wound around a non-metallic core. Companies that manufacturer transformers are listed on the Inductor /Transformer Manufacturer page. An air-core transformer symbol is shown with out vertical lines between the windings.
Audio Transformer. A transformer designed to operate in the audio frequency range of 20Hz to 20kHz.
MIL Specs; MIL-PRF-27/307A Audio Frequency Transformer.
Auto-Transformer. A transformer with only one winding. The secondary side [same winding] has two or more fixed taps or a movable tap and a common point with the primary. The common point may also be located on the 'low-side' of the transformer.
Balum Transformer. Refer to the definition of Balun.
Center Tap. [CT] A tap or connection at the center of the primary or secondary winding. Pin 2 in the diagram above is a center tap connection.
Core. The material placed within a coil to intensify the magnetic field. Possible core materials include iron and even air cores. Also refer to Companies making transformer cores.
Coupling Transformer. A transformer used to couple or connect two different circuits. A coupling transformer may be a 1:1 winding transformer, a Step Up transformer or a Step Up transformer.
Eddy Current. Induced circulating currents in a conducting material that are caused by a varying magnetic field. The current induced in a conductor [the transformer core] subjected to a varying magnetic field. Eddy current results in transformer heating due to current flow in the core, also called I2R losses [power loss = I x I x R]. The amount of heating in the core is dependent on the amount of current flowing in the core and the resistance of the core.
E-Transformer. A differential transformer using an E-shaped core. More detail; E-Transformer. The E-core transformer also exposes more of the windings to air reducing the amount of heat building up in the core.
Ferrite Core. A transformer using a ceramic containing iron oxide as the core. A ferrite core has a high impedance lowering any eddy current loses.
Horizontal Transformer. A physical layout that results in the transformer winding being horizontal to the mounting plane. A transformer that is opposite of a vertically mounted transformer.
Hybrid Coil. A single transformer that effectively has three windings, and which is designed to be configured as a circuit having four branches, i.e., ports, that are conjugate in pairs.
Iron Core Transformer. A transformer that uses iron to separate the primary and secondary windings. An iron-core transformer symbol is shown with vertical lines between the windings. See shell core.
Isolation Transformer. A transformer used to isolate or decouple two different circuits. An isolation transformer could be used to prevent unwanted interaction between two circuits, block DC or electrically isolate different systems.
An Isolation Transformer may be nothing more than a transformer with better insulation between the primary and secondary windings. Pin 4 in the transformer symbol is a shield.
Laminated Core. A transformer core made of separate pieces of metal [iron], individual laminated and than stacked together to form the core.
Polarity. The phase change or polarity between the primary winding and the secondary winding is shown with polarity dots on the transformer symbol. The dot indicates the same polarity.
Primary. The input side of a transformer. The primary side of a transformer connected to the electrical source. The primary transformer winding normally is used to set up current that is then transferred to one or more secondary windings of the transformer.
RF Transformer. A transformer specially designed for use with RF (radio frequencies). An RF transformer is wound onto a tube of nonmagnetic material and has a core of either powdered iron or air.
Rod Core. A circular slug or tube used as the transformer core.
Schematic Transformer Symbols
Schematic Symbols. The symbols used to represent a transformer on a schematic drawing. A number of transformer symbols are shown in the graphic above. A schematic diagram for a Step Up Transformer symbol using a different number of coil turns between the primary and secondary side is shown on the MIL-1553 Interface page.
Secondary. The winding on the output side of a transformer. The transformer secondary may have more turns than the primary [Step-up] or less turns than the primary [Step-down].
Shell Core. The core of a transformer comprised of E shaped and I shaped metal sections. The sections are than butted together to form the laminations, which are then insulated from each other and pressed together to form the core.
Shielded Transformer. Also called electrostatic shield. A transformer encased in metal shield or box to shield the transformer from electrical fields, or shield external circuits from the transformer.
Step-Down Transformer. A transformer so constructed that the number of turns in the
secondary winding is less than the number of turns in the primary winding. A Step Down Transformer is construction to provide less voltage in the secondary circuit than in the primary circuit. A Multi-tapped Step-down transformer symbol is shown to the right. The example is using 400Hz, but that does not effect the schematic symbol.
Step-Up Transformer. A Step Up Transformer is constructed so that the number of turns in the secondary winding is more than the number of turns in the primary winding. This construction will provide more voltage in the secondary circuit than in the primary circuit. In many cases a Step Up Transformer Symbol will like just like a 1:1 transformer. However in a small number of cases a Step Up Transformer Symbol will show more windings on the secondary side than the primary side in the schematic.
Switching Transformer. Mil Spec; MIL-PRF-27/366 Switching Transformer.
Tapped Coil. An inductor or transformer that has a tap or additional terminal located along the winding.
Transformer. A device composed of two or more coils, linked by magnetic lines of force, used to transfer energy from one circuit to another, at the same frequency but not always at the same voltage.
Transformer Efficiency. The ratio of output power to input power, generally expressed as a percentage [Voltage x Current].
Toroidal Core. A doughnut shaped core.
Toroidal Transformer. A round shaped magnetic core with windings forming a transformer. The graphic in the right side-bar shows a Toroidal transformer with dual winding wound around the same core.
Turns Ration. The ratio of the number of turns in the primary winding to the number of turns in the secondary winding of a transformer. The turns ratio indicates if the transformer is a step-up, step-down or 1-to-1 voltage change. Note that the winding on a transformer secondary could produce both a Step-up and Step-down with in the same transformer.
Variable frequency transformer. [VFT] A VFT system provides a means to control power between two grids [synchronous or asynchronous].
Windings. The coils of a transformer. The primary winding is connected to the source in the circuit, while the secondary winding is connected to the circuit load. A transformer winding is wound around a core and covered in enamel to prevent the wires from shorting together.