Classification and Function of Transformers

Transformers can be said to be related to our daily production and life, such as: our mobile phone chargers, home refrigerators, air conditioners, fans, rice cookers, etc., there are transformers inside, but these products are for the safety of users. , Are all wrapped in the outer shell of the product. And some friends with thin wires will find that no matter in the city or in the country, they will see some transformers on the poles. This type of converter is to convert our high-voltage wires to a voltage that can be used normally by our electrical appliances. Only the classification of the transformer is different. Its role is different.

1. Power transformer:

The power transformer is mainly used to couple electrical energy from the power line to the circuit system, or to one or more components of the system. Power transformers used with solid-state circuits are called rectifier transformers. The rated value of the power transformer is given based on the maximum voltage and current carrying capacity of the secondary.

2. Distribution transformer:

Pole-type distribution transformers are used to provide a relatively small amount of electricity to residences. It is used at the end of the power utility transmission system.

3. Autotransformer:

Autotransformer is a special type of power transformer. It consists of a single continuous winding, tapped on one side to provide a step-up or step-down function. This is different from the traditional dual-winding transformer. The primary and secondary sides of the traditional dual-winding transformer are completely isolated from each other, but are magnetically connected through a common magnetic core. The windings of the autotransformer are electrically and magnetically interconnected.

Autotransformers were initially cheaper than two-winding transformers of similar ratings. It also has better regulation (smaller pressure drop) and higher efficiency. In addition, it can also be used to obtain a three-wire 240/120 volt service neutral line, just like the secondary of a two-winding transformer. Autotransformers are considered unsafe for use in ordinary power distribution circuits. This is because the high-voltage primary circuit is directly connected to the low-voltage secondary circuit. 

4. Isolation transformer:

The isolation transformer is a very unique transformer. Its turns ratio is 1:1. Therefore, it does not increase or decrease the voltage. Instead, it serves as a safety device. It is used to isolate the ground conductor of the power cord from any part of the chassis or circuit load. If contact is made on the secondary winding of the transformer, the use of an isolation transformer will not reduce the risk or electric shock.

Technically speaking, any real transformer, whether used for signal transmission or power supply, is isolated, because the primary and secondary are not connected by conductors, but by induction. However, the transformer whose main purpose is to isolate the circuit (as opposed to the more common voltage conversion transformer function) is usually called an isolation transformer.

5. Instrument transformer:

In order to measure the high value of current or voltage, it is best to use a standard low-range measuring instrument with a specially constructed transformer (also called a precision proportional transformer). As the name suggests, the role of an accurate ratio transformer. It converts at an accurate rate, allowing the connected instrument to measure current or voltage without actually running full power through the instrument. A relatively small amount of power needs to be converted because its only load (called burden) is the precision moving component of an ammeter, voltmeter, or wattmeter.

6. current transformer:

The current transformer has a primary coil with one or more turns of thick wire. It is always connected in series in the circuit where the current is to be measured. The secondary coil consists of multiple turns of thin wire and must always be connected across the ammeter terminals. The secondary of the current transformer must not be opened. This is because the primary is not connected to a constant source. The possible primary voltage range is wide, because the device can be connected to many types of conductors. The secondary must always be available (closed circuit) to react with the primary to prevent the core from being completely magnetized. If this happens, the instrument will no longer read accurately.

Clamp-on ammeters work similarly. By opening the clamp and placing it around the current-carrying conductor, the conductor itself acts as a single-turn primary. The secondary and ammeter are conveniently installed in the handle of the device. The dial allows accurate measurement of multiple current ranges. On-site current transformer Current transformer is a kind of instrument transformer. They are used to measure current.