plaanner transformer

Introduction to basic knowledge of transformer

The transformer is composed of an iron core (or magnetic core) and a coil. The coil has two or more windings, of which the winding connected to the power supply is called the primary coil, and the other windings are called the secondary coil.

1、 Classification

Classification by cooling mode: dry type (self cooling) transformer, oil immersed (self cooling) transformer and fluoride (evaporative cooling) transformer.

Classified by moisture-proof method: open type transformer, potted type transformer and sealed type transformer.

Classification according to iron core or coil structure: core transformer (inserted core, C-type core and ferrite core), shell transformer (inserted core, C-type core and ferrite core), ring transformer and metal foil transformer.

Classification according to the number of power phases: single-phase transformer, three-phase transformer and multi-phase transformer.

Classification by use: power transformer, voltage regulating transformer, audio transformer, intermediate frequency transformer, high frequency transformer and pulse transformer.

2、 Characteristic parameters of power transformer

1. Operating frequency

The loss of transformer core is closely related to the frequency, so it should be designed and used according to the use frequency, which is called the working frequency.

2. Rated power

Under the specified frequency and voltage, the transformer can work for a long time without exceeding the output power of the specified temperature rise.

3. Rated voltage

It refers to the voltage allowed to be applied on the coil of the transformer, which shall not be greater than the specified value during operation.

4. Voltage ratio

It refers to the ratio of primary voltage to secondary voltage of transformer, which is different from no-load voltage ratio and load voltage ratio.

5. No load current

When the secondary of the transformer is open circuit, there is still a certain current in the primary, which is called no-load current. No load current consists of magnetization current (generated magnetic flux) and iron loss current (caused by core loss). For 50Hz power transformer, the no-load current is basically equal to the magnetizing current.

6. No load loss

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

7. Efficiency

Is the percentage of the ratio of secondary power P2 to primary power P1. Generally, the higher the rated power of the transformer, the higher the efficiency.

8. Insulation resistance Qingzhou global electronics

It indicates the insulation performance between each coil of transformer and between each coil and iron core. The insulation resistance is related to the performance, temperature and humidity of the insulating materials used.

3、 Characteristic parameters of audio frequency transformer and high frequency transformer

1. Frequency response

It refers to the characteristic that the secondary output voltage of the transformer changes with the operating frequency.

2. Passband

If the output voltage of the transformer at the intermediate frequency is U0, the frequency range when the output voltage (input voltage remains unchanged) drops to 0.707u0 is called the passband B of the transformer.

3. Primary and secondary impedance ratio

The primary and secondary impedance of transformer are connected with appropriate impedance RO and RI to match the primary and secondary impedance of transformer, then the ratio of RO and RI is called the primary and secondary impedance ratio. In the case of impedance matching.