Adjusting Method of Adjustable Inductor

　　In the specific power supply equipment, we mainly use the method of combining the iron core and the circuit to change the inductance of the inductor. They are the following three methods.

1) Saturated Inductance Method

The first method is to wind two windings on the core. One is the working winding, which is used to pass AC; the other is the control winding, which is used to pass DC. By changing the magnitude of the direct current in the control winding, the saturation of the iron core can be changed, thereby changing the equivalent inductance of the working winding. But this method is relatively old. Saturated inductors and magnetic amplifiers work on the basis of this saturated inductance method.

2) Switch Control

The second method is to connect a bidirectional thyristor switch in series in the inductor circuit. By turning on and off the bidirectional thyristor, the equivalent inductance of the inductor can be changed. Nowadays, a large number of sinusoidal energy distributor-type AC stabilized power supplies researched, developed and produced at home and abroad are all based on this switch-controlled inductance method.

3) Quadrature Core Control

The third method is to rotate one half of the C-shaped core by 90° and connect the other half. One half of the core is wound with a working winding to pass AC; the other half of the core is wound with a control winding to pass DC. By changing the magnitude of the direct current, the inductance of the working winding can be continuously changed. This method is usually applied to switching power supplies, inverter power supplies, AC regulated power supplies, and power AC series compensators and phase shifters. Japan calls this kind of orthogonal shape soft ferrite core, which is called SX core.

Commonly Used Adjustable Inductors

Here we mainly explain the three commonly used adjustable inductors.

1. Oscillating Coil for Semiconductor Radio

This kind of oscillating coil forms a local oscillating circuit with variable capacitors in semiconductor radios. It is used to generate a local oscillator signal whose radio signal received by the input tuning circuit is higher than 465kHz. Its exterior is a metal shield. Its interior is composed of a nylon lining frame, I-shaped magnetic core, magnetic cap, and pin base. The I-shaped magnetic core has a winding made of high-strength enameled wire. Its magnetic cap is mounted on a nylon frame in the shield. In this way, it can be rotated up and down, and the inductance of the coil can be changed by changing the distance between it and the coil. The internal structure of the TV IF trap coil is similar to the oscillation coil, except that the magnetic cap can adjust the magnetic core.

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