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An electromagnetic interaction is used to convert voltage
Jun 08, 2018

A transformer is a device that converts alternating voltage, current, and impedance. When an alternating current flows in the primary coil, an alternating magnetic flux is generated in the iron core (or core), causing a voltage (or current) to be induced in the secondary coil. The transformer consists of a core (or core) and a coil, and the coil has two or more windings, wherein the winding of the power supply is called the primary coil and the rest of the winding is called the secondary coil.


First, the principle of transformer production:


In a generator, whether the coil moves through a fixed coil through a magnetic field or a magnetic field, a potential can be induced in the coil. In both cases, the value of the magnetic flux does not change, but the amount of magnetic flux that intersects the coil has Change, this is the principle of mutual induction. A transformer is a device that uses electromagnetic induction to convert voltage, current, and impedance.


Second, classification


Classified by cooling method: dry (self-cooling) transformers, oil-immersed (self-cooling) transformers, and fluoride (evaporative cooling) transformers. According to moisture classification: open transformers, potted transformers, sealed transformers.


According to core or coil structure classification: core type transformer (insert core, C type core, ferrite core), shell type transformer (insert core, C type core, ferrite core), Toroidal transformers, metal foil transformers.

According to the number of phases of the power supply: single-phase transformers, three-phase transformers, multi-phase transformers.


Classified by purpose: power transformers, regulator transformers, audio transformers, intermediate frequency transformers, high frequency transformers, pulse transformers.


Third, the characteristics of power transformer parameters


The working frequency transformer core loss and frequency is very large, so it should be designed and used according to the frequency of use, this frequency is called the operating frequency.


Rated power at a specified frequency and voltage, the transformer can work long-term, without exceeding the output power of the specified temperature rise.


The rated voltage refers to the allowable voltage applied to the coil of the transformer and must not exceed the specified value during operation.


The voltage ratio refers to the ratio of the transformer primary voltage to the secondary voltage, with the difference between the no-load voltage ratio and the load voltage ratio.


When the no-load current transformer is open, the primary still has a certain current. This part of the current is called the no-load current. The no-load current consists of a magnetizing current (flux producing) and an iron loss current (caused by the core loss). For a 50Hz power transformer, the no-load current is substantially equal to the magnetizing current.


No-load loss refers to the power loss measured at the primary when the transformer secondary is open. The main loss is the core loss, followed by the loss (copper loss) of the no-load current on the copper resistance of the primary coil. This part of the loss is very small.


Efficiency refers to the percentage of the ratio of secondary power P2 to primary power P1. In general, the higher the rated power of the transformer, the higher the efficiency.


The insulation resistance represents the insulation performance between the coils of the transformer and between the coils and the iron core. The level of insulation resistance is related to the performance of the insulating material used, the temperature and the degree of humidity.


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