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A leakage transformer, also called a stray-field transformer, has a significantly higher leakage inductance than other transformers, sometimes increased by a magnetic bypass or shunt in its core between primary and secondary, which is sometimes adjustable with a set screw. This provides a transformer with an inherent current limitation due to ...
The coupling factor is defined as: , = where P 1 is the input power at port 1 and P 3 is the output power from the coupled port (see figure 1). The coupling factor represents the primary property of a directional coupler.
To match the impedances, both cables must be connected to a matching transformer with a turns ratio of 2:1. In this example, the 300-ohm line is connected to the transformer side with more turns; the 75-ohm cable is connected to the transformer side with fewer turns. The formula for calculating the transformer turns ratio for this example is:
Diagram of center-tapped transformer. In electronics, a center tap (CT) is a contact made to a point halfway along a winding of a transformer or inductor, or along the element of a resistor or a potentiometer. Taps are sometimes used on inductors for the coupling of signals, and may not necessarily be at the half-way point, but rather, closer ...
One of the windings of the transformer had a variable capacitor connected across it to make a tuned circuit. A variable capacitor (or sometimes a variable coupling coil called a variometer) was used, with a knob on the front panel to tune the receiver. The RF stages usually had identical circuits to simplify design.
Coupling can be deliberate as part of the function of the circuit, or it may be undesirable, for instance due to coupling to stray fields. For example, energy is transferred from a power source to an electrical load by means of conductive coupling , which may be either resistive or direct coupling .
A double-tuned transformer from a radio receiver intermediate-frequency amplifier with its screening can removed. A double-tuned amplifier is a tuned amplifier with transformer coupling between the amplifier stages in which the inductances of both the primary and secondary windings are tuned separately with a capacitor across each.
Fig. 1 L P σ and L S σ are primary and secondary leakage inductances expressed in terms of inductive coupling coefficient under open-circuited conditions.. The magnetic circuit's flux that does not interlink both windings is the leakage flux corresponding to primary leakage inductance L P σ and secondary leakage inductance L S σ.