A Magnetic Amplifier (Mag Amp) is an electrical device that uses magnetic saturation to control the flow of current in a circuit. It operates based on the principle of magnetic impedance variation, and it can be employed as a variable reactor to control the amount of inductance in a circuit. The basic principles behind the operation of a Mag Amp and its use as a variable reactor are as follows:
Magnetic Impedance Variation: The core principle of a Mag Amp lies in the variation of magnetic impedance. It utilizes a magnetic core that can be driven into saturation, which alters its permeability and thus affects the impedance of the magnetic circuit.
Magnetic Core: The Mag Amp typically consists of a ferromagnetic core made of materials like iron, steel, or other magnetic alloys. The core has a primary winding (input coil) and a secondary winding (output coil).
Control Winding: The Mag Amp also features a control winding (control coil) that is connected in series with the load or the circuit where the current needs to be regulated. This control winding is responsible for controlling the saturation level of the magnetic core.
Saturation: When a direct current (DC) flows through the control winding, it creates a magnetic field that influences the magnetic properties of the core. As the control current increases, the core approaches saturation, and its permeability decreases, resulting in higher magnetic impedance.
Variable Reactor: By adjusting the control current, the level of magnetic saturation can be controlled. Since the impedance of the magnetic circuit is related to the magnetic permeability of the core, changing the level of saturation effectively varies the reactance or inductance of the Mag Amp.
Effect on Load Current: The variation in reactance or inductance affects the current flow in the load circuit connected in series with the control winding. As the magnetic impedance increases (higher saturation), the impedance seen by the load increases, which results in reduced current flow. Conversely, decreasing the control current reduces saturation and lowers magnetic impedance, leading to increased current flow.
Applications: Mag Amps find applications in various areas, such as power control, motor drives, and voltage regulation. When used as a variable reactor, they can be employed to control the amount of reactive power in a circuit, making them useful in applications where variable inductance is required.
Advantages and Disadvantages: The advantages of Mag Amps include their simplicity, lack of moving parts (which improves reliability), and high-speed response. However, they also have some drawbacks, such as power dissipation in the control winding and core losses, which can limit their efficiency in high-power applications.
In summary, a Magnetic Amplifier (Mag Amp) operates on the principle of magnetic impedance variation through saturation of a magnetic core. By controlling the current through the control winding, the Mag Amp can act as a variable reactor, adjusting the inductance and, consequently, the amount of reactive power in a circuit.