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    Step Up & Down Transformers

    What is Transformer?

    A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. It can be designed to step up or step down voltages and works on the magnetic induction principle. When an AC current is passed through the primary coil, an AC magnetic flux is generated in the iron core, causing a voltage (or current) to be induced in the secondary coil. It is composed of an iron core and a coil. The coil has two or more windings. The winding connected to the power supply is called the primary winding, and the remaining windings are called the secondary winding.

    Working Principle of Transformer:

    Transformer mainly uses the principle of electromagnetic induction to work. The specific process is when an AC voltage U1 is applied to the primary side of the transformer, and the current flowing through the primary winding is I1, the current will generate alternating magnetic flux in the iron core, which makes the primary winding and the secondary winding electromagnetically connections.

    According to the principle of electromagnetic induction, the electromotive force will be induced when the alternating magnetic flux passes through these two windings. Its magnitude is proportional to the number of winding turns and the maximum value of the main magnetic flux. The voltage on the side with more winding turns is higher, and the voltage on the side with less winding turns is lower. When the secondary side of the transformer is open, that is, when the transformer is no-load, the voltage at the primary and secondary terminals is proportional to the number of turns of the primary and secondary windings. That is, U1/U2=N1/N2, but the primary and secondary frequencies are consistent, so as to realize the voltage change. The working principle of the transformer can be understood from the figure below.

    Working principle of transformer


    Main Technical Parameters of Transformer:

    1. Voltage. The primary rated voltage of a transformer refers to the voltage value specified by the strength of the insulating material used in the transformer. The primary rated voltage of a transformer refers to the voltage value specified by the strength of the insulating material used in the transformer. The secondary rated voltage is the voltage value at both ends of the secondary after the rated voltage is applied to the transformer at no load. The two rated voltages are represented by U1N and U2N respectively. Single-phase transformer U1N, U2N refers to the effective value of primary and secondary AC voltage. The three-phase transformer U1N, U2N refers to the effective value of the primary and secondary line voltage.
    2. Rated Current. It refers to the maximum current allowed to flow in the primary and secondary windings of the transformer under the conditions of allowable temperature rise. The secondary current of the transformer is represented by I1N and I2N respectively. Single phase transformers I1N and I2N refer to the effective value of the current. Three phase transformer refers to the effective value of line current.
    3. Rated Capacity. The rated capacity represents the maximum power that the transformer is allowed to transmit when it is working. The rated capacity of a single-phase transformer is the product of the secondary rated voltage and rated current; the rated capacity of a three-phase transformer is also the product of the secondary rated voltage and rated current. The rated capacity is indicated by the letter S, and the unit is volt-ampere (V-A).
    4. Temperature Rise. Temperature rise refers to the value that the transformer is allowed to exceed the ambient temperature during rated operation. It depends on the heat resistance class of the transformer insulation material.

    Functions of Transformer:

    1. Ensure the safety of electricity. There are many types of transformers, but each type of transformer is a device that uses the principle of electromagnetic induction to change the AC voltage. Therefore, the use of each transformer can ensure the safety of electricity. By changing the AC voltage without changing the power source, the current can be changed, which essentially enables people to use electricity safely.
    2. Use transformer to step up and step down. The transformer can make voltage step up & down. We often use various voltages. For example, we need different voltages for household lighting power and industrial safety power. All of these are inseparable from the transformer. Using the transformer, we can reduce the voltage to the required voltage through the principle of electromagnetic mutual inductance, and reduce the voltage loss.
    3. Impedance matching voltage. This function is most commonly used in electronic circuits. Generally speaking, electronic factories will use transformers for impedance matching to make the signal flow smoothly. Therefore, companies that require different voltages in the same environment can manufacture multi-winding transformers to satisfy the daily needs of workers.

    Different Types of Transformers:

    Isolation Transformer

    Isolation transformer refers to a transformer with electrical isolation between the input winding and the output winding. It is widely used in the electronic industry or industrial and mining enterprises, machine tools and mechanical equipment in the general circuit control power supply, safety lighting and indicator power.

    Principle: The principle of isolation transformer is the same as that of ordinary transformer. They all use the principle of electromagnetic induction to step up & down voltage. Isolation transformer generally refers to a 1:1 transformer. Due to the secondary is not connected to the ground, there is no potential difference between any line of the secondary and the ground, so it is safe to use and often used as a maintenance power supply.

    Function:It can completely insulate the electrical on the primary side and the secondary side, and also isolate the circuit. In addition, the high-frequency loss of its iron core is used to prevent high-frequency clutter from entering the control loop. Using an isolation transformer to suspend the secondary to the ground can only be used in occasions where the power supply range is small and the line is short. At this time, the capacitance current of the system to ground is too small to cause personal injury. Another important role is to protect personal safety! It can isolate people from dangerous voltages.


    1. Boot but no display. If there is insurance, the three-phase isolation transformer has no display and no grid, showing that the lamp industry is faulty. The technician should open the transformer and check that the rectifier circuit has an infinite current resistance burnt. At the same time, check whether the rectifier diode is dangerously disconnected, and repair or replace these parts according to the inspection.
    2. The voltage is higher or lower than normal. When the three-phase isolation transformer is running, it is not zero and the protection circuit does not operate, but the output voltage is much higher or lower than the normal value. At this time, if the fault phenomenon changes with the voltage change, then the voltage regulator potentiometer needs to be adjusted; if the output does not change or the change is very small, then it may be that the sampling differential amplifier circuit is faulty.
    3. Burn insurance at boot. If the three-phase isolation transformer burns the fuse and the output voltage is zero as soon as it is turned on, it is necessary to consider that it is caused by the breakdown of the switch tube and the short-circuit of the emitter and the collector. At this time, the switch tube can be removed first, and the resistance of the emitter and collector to the ground can be measured. If it is zero or very small, just replace it.

    Single Phase Isolation Transformer

    Single phase isolation transformers are suitable for circuits with voltages ranging from 50-60Hz to 500V. They are usually used as power supplies for machine tool electrical appliances or local lighting and various imported equipment. The ambient air temperature is from -5°C to +40°C, and the 24-hour average does not exceed +35°C. Single phase isolation transformer cannot be installed at altitudes higher than 200 meters.

    Isolation transformer single phase 


    1. Anti-interference: After passing the Y/△-connected isolation transformer, it can prevent the transmission of some harmonics.
    2. Impedance transformation: Increasing the impedance of the system, so that the protection devices are easy to cooperate.
    3. Stabilize system voltage: When starting heavy load equipment, reducing the impact on the system voltage.
    4. Prevent system grounding: When single-phase grounding occurs on the load side of the isolation transformer, it will not cause single-phase grounding of the entire system.
    5. Reduce short-circuit current: When a short-circuit accident occurs on the load side, the short-circuit current of the system is limited.

    Three Phase Isolation Transformer

    Three phase isolation transformers are widely used in industrial and mining enterprises, power plants, airports, high-rise buildings, subways and other places with high safety and fire protection requirements, for step up & down voltage, lighting equipment, power supply, and rectifier power supply. It is mainly used as the isolation equipment for the purification power supply and the power grid of the precision measurement test system. You can find out the price of isolation transformers on ATO product homepage.

    Isolation transformer 3 phase


    1. Greener: As energy shortages and the environment intensify, energy conservation and environmental protection are essential. The development and introduction of new materials will enable future three phase isolation transformers to save energy, to have higher efficiency, and operate more quietly. 
    2. High safety factor: Checking every link from design, production, process, quality inspection, to ensure that the power equipment is foolproof. In the future, three-phase isolation transformers will go through further reliability certification in terms of safety, and power safety will be the goal of the unremitting efforts of design manufacturers.
    3. Capacity expansion: As the urban population continues to expand, the demand for electricity is also increasing. Expanding capacity is the fundamental solution. Through this way, it can satisfy the demand for electricity during the peak period of the urban population.

    Toroidal Transformer

    Toroidal transformer is a large type of electronic transformer, which has been widely used in household appliances and other electronic equipment with high technical requirements. Its main purpose is as a power transformer and isolation transformer. Toroidal transformer has been widely used in computers, medical equipment, telecommunications, instruments and lighting.

    Toroidal transformer


    1. High efficiency. The transformer core is made of continuous oriented silicon steel strips. After annealing, it will form a highly consistent magnetic flux guide. At the same time, the windings of the toroidal transformer are wound tightly covering the toroidal core. The magnetic flux the density is higher because the toroidal transformer can achieve a high electrical efficiency of 95%.
    2. The vibration noise is small. And the iron core has no air gap to reduce the noise of the iron core induced vibration. The winding evenly and tightly wraps the ring iron core, effectively reducing the "buzzing" sound caused by magnetostriction.
    3. It is easy to install. Toroidal transformer with only one mounting screw in the center, which is especially easy for quick installation and disassembly in electronic equipment.


    1. Electrical control. Such as used for current and voltage transformers. High-precision, high-stability transformer made with toroidal transformer technology. New high-performance magnetic materials, such as nanocrystalline alloys can be used as magnetic cores, equipped with sophisticated intelligent instruments and special testing methods to ensure accurate transformer parameters and complete performance.
    2. Medical equipment. Toroidal transformers specially designed and manufactured for medical equipment. In addition to high efficiency, high reliability and high safety requirements. It also especially strengthens the electrical strength and improves the resistance to damp and heat. It is required to add a thermal fuse inside the transformer to ensure reliability.
    3. Others. Toroidal transformers can also be used in various power inverters, such as solar and wind power generation systems. The use of toroidal transformer can greatly improve the overall efficiency of the inverter power supply.

    Problems in Use:

    1. Overload use. The secondary use of the toroidal transformer exceeds the rated voltage and current, causing the temperature rise of the transformer to exceed the specified value, and the aging of the insulation material causes an internal short circuit and burns out. If there is a possibility of overload, the overload range must be considered in the design.
    2. The voltage primary is plugged into the high-voltage power supply. If you accidentally insert the 110V toroidal transformer into the 220V power supply, the transformer will be burnt out instantly.
    3. The grid voltage varies greatly day and night. The toroidal transformer is designed to allow the grid voltage to vary by ±10%. If the grid voltage fluctuation range exceeds 10%, the excitation current of the transformer will increase and the temperature rise will affect the life of the transformer; if the grid voltage is lower than -10%, the output will be under-voltage current. The load is not working as normal.
    4. Load short.


    1. The transformer noumenon in good condition without burning. The primary and secondary windings of the toroidal transformer have no obvious burning phenomenon. It can be judged that the built-in protector of the toroidal transformer is fused, or the primary winding of the transformer is due to the working environment, enameled wire material or other factors that may cause the primary disconnection.
    2. Transformer primary winding turns yellow and burnt. The primary excitation current of the toroidal transformer is increased, and the primary winding of the toroidal transformer is burnt due to the following reasons: the transformer secondary circuit is short-circuited; the secondary load does not match the output power; transformer primary winding rated input voltage does not match; the design does not fully consider the impact of the use environment.
    3. The primary of the transformer is good and the secondary has no output. The secondary circuit of the toroidal transformer is disconnected, resulting in poor contact or complete disconnection after aging.
    4. The primary and secondary of the transformer are good, and the heat generated by the insertion circuit is high. The load does not match the power of the toroidal transformer, or the input voltage is too high.
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