How to distinguish between non self coupling transformers

This is not the case, in principle, the autotransformer has only one coil, and the low voltage is part of the high voltage coil, but the actual product is not. In the actual product, the auto-transformer and non-auto-transformer are divided into high and low voltage coils, but the number of turns of the high-voltage coil of the ordinary transformer is the ratio of the phase voltage to the turn potential, and the end of the coil is led out of the grounding by the neutral point bushing, but the number of turns of the auto-transformer high-voltage coil is less, which is equal to the ratio of the high-voltage phase voltage to the voltage and the turn potential, the tail end of the coil is connected with the head end of the low-voltage coil, which is led out by the low-voltage bushing, and the tail end of the low-voltage coil is grounded through the neutral point bushing.

For ordinary transformers, the capacity of the high-voltage coil is the same as the capacity of the low-voltage coil, which is equal to the rated capacity of the transformer. However, the autotransformer is different, there is a direct electrical connection between the high and low voltage, the low-voltage coil is equivalent to a part of the high-voltage coil, part of its energy is directly conducted, and part of it is transmitted through electromagnetic coupling, so the capacity of the high-voltage and low-voltage coils is lower than the rated capacity of the transformer, and there is an autocoupling benefit coefficient.

The primary coils of ordinary transformers are independent! It works by mutual inductance potential, and its wire diameter is also different.

The self-coupling transformer has only one coil, which works by self-induction potential, and the primary is drawn out by the tap, and then the tap or the secondary is drawn from the sliding brush! Neutral line sharing. Its efficiency is higher than that of ordinary transformers! However, due to the fact that the initial level is not isolated, the safety is poor.

Autotransformers.

The primary and secondary windings are one, and the secondary winding is part or all of the primary winding.

The advantages of an autotransformer equivalent to an isolation transformer are the same capacity: cheap, small and lightweight. Easy to handle and install.

Same**: The capacity of the autotransformer is twice as large as that of the isolation transformer! The disadvantage is that there is no way to isolate the filter.

Can only be used as a boost or buck. There is a voltage difference between it and the ground, which can easily cause the risk of electric shock!!

The main advantages and disadvantages of autotransformers.

First, the main advantages of autotransformers.

1. Low material cost. Under the same rated capacity, the size of the autotransformer is small, and the silicon steel sheet and copper wire are more economical;

2. High efficiency. Under the same rated capacity, the copper loss and iron loss are reduced correspondingly, so the autotransformer has higher efficiency.

3. Easy to transport and install. Under the same rated capacity, the size of the autotransformer is small, so it is light in weight, small in area, and easy to transport and install.

Second, the main disadvantages of autotransformers.

1. The short-circuit impedance scalar value is small, and the short-circuit current is large.

2. Poor insulation performance of low-voltage winding. The secondary winding is tapped directly on the primary winding, and there is a direct electrical connection between the two, and there is no isolation effect.

3. The grounding fault on the high-voltage side directly causes the voltage on the low-voltage side to rise. When single-phase grounding occurs on the high-voltage side, it will cause the non-grounding voltage on the low-voltage side to rise higher, resulting in the breakdown of insulation to the ground, so the neutral point must be reliably grounded.

What happens when a time relay burns out.

If the neutral point of the autotransformer is not grounded, when a single-phase grounding fault occurs in the high-voltage power grid, an overvoltage occurs on the secondary winding. As can be seen in the figure, when phase A is grounded, the relative ground voltage of the secondary BM U is larger than its normal line voltage UAMBM, and the larger the primary and secondary transformation ratio, the larger the overvoltage multiple, then the transformer insulation is easy to break down, so the neutral point of the autotransformer must be dead grounded.

The primary and secondary stages of the autotransformer share a set of coils, which are generally directly connected to the power supply line 380V 220V, if the coil touches the shell at a certain point, it will threaten personal safety and even endanger life, so the autotransformer shell must be directly grounded to protect!

Agree with the upstairs view that it is mainly for safety It can work without grounding is the secondary winding, and there is a safety hazard when it burns out or is short-circuited.

Mainly for the safety considerations of all aspects, because the primary pole of the autotransformer is on the same group of windings, if there is no common grounding, the primary high voltage will inevitably rush into the low voltage, directly causing the low voltage to the ground to appear high voltage.

The principle of an autotransformer is to produce a step-up or step-down by pulling out several heads in its own windings to form relatively different voltages at the common points. When used as a step-down transformer, a part of the line turns are extracted from the winding as a secondary winding; When used as a step-up transformer, the applied voltage is only applied to the turn-part of the winding. Usually the part of the winding that belongs to both primary and secondary is called the common winding, and the rest of the autotransformer is called the series winding, and the autotransformer with the same capacity is not only small in size compared with the ordinary transformer, but also has high efficiency, and the larger the transformer capacity, the higher the voltage This advantage is more prominent.

Therefore, with the development of power system, the improvement of voltage level and the increase of transmission capacity, autotransformers have been widely used due to their large capacity, small loss and low cost.

Answer: First, the working principle of the self-coupling transformer.

Wound two or more coils around a closed core, when one coil is fed into the AC power supply (that is, the primary coil), an alternating current flows through the coil, and this alternating current generates an alternating magnetic field in the core, and the alternating main magnetic flux generates its own induced electromotive force in the primary coil, and at the same time, the other coil (that is, the secondary coil) induces mutual inductive electromotive force.

Second, the characteristics of the self-lotus transformer.

1. Because the calculated capacity of the autotransformer is less than the rated capacity.

2. Because the short-circuit impedance standard value of the autotransformer is smaller than that of the double-winding transformer, the voltage change rate is smaller, but the short-circuit current is larger.

3. Due to the autotransformer.

There is a direct connection between the primary and secondary electricity, and when the high-voltage side is over-voltaged, it will cause serious overvoltage on the low-voltage side.

4. In general transformers.

Because it is three-phase, you have a ring core, you rise from the line voltage of 280V to 380V, and the phase voltage is changed to 161V to 220V, so I help you calculate a parameter for your reference; With 70 high 85 inner diameter 170 outer diameter, primary with 2 posts two around 191 turns auto-coupling boost 60V with three around 72 turns, and then connect the primary tail with the secondary head, and then connect the primary head back to zero to become a three-phase 280V auto-coupling boost 380V, three-phase transformer.

I recommend going and buying a three-phase 15 to 20 kVA fully automatic voltage regulator.

Reason: You buy iron core, buy copper wire, the cost is not small after the effort is entangled, and the voltage changes slightly will not be used, the voltage will burn out your motor, and even your 15kw load will be connected to the input voltage from 280 volts.

The following points should be paid attention to when debugging the self-coupling transformer.

1.When measuring the motor, you should measure the wire before connecting it to the transformer, if the transformer is measuring, the transformer may cause measurement failure.

2.When measuring the self-lotus transformer, you can see whether the phase sequence of the transformer after the transformer is consistent with the phase sequence after the normal operation of the equipment, if it is inconsistent, it should be adjusted to be consistent, otherwise it will rotate forward when starting, and suddenly become reversed during operation, and the equipment will definitely trip.

<> note: After the above two items are confirmed, the main circuit is disconnected first, and the control loop is powered to see if the action of the contactor is correct

Hope, thank you.

1. An autotransformer is a special transformer that shares a set of coils for the output and input. Boosting and stepping down is achieved with different taps. The voltage of the tap is reduced if there is less than the common coil. The voltage of the partial tap that is more than the common coil increases.

2 In fact, the principle is the same as that of an ordinary transformer, except that its original coil is its secondary coil. The general transformer is a primary coil on the left through electromagnetic induction, so that the secondary coil on the right generates voltage, and the autotransformer affects itself.

3. The autotransformer is a transformer with only one winding, and when used as a step-down transformer, a part of the line turns are extracted from the winding as a secondary winding; When used as a step-up transformer, the applied voltage is only applied to the turn-part of the winding. Usually the part of the winding that belongs to both primary and secondary is called the common winding, and the rest of the autotransformer is called the series winding, and the autotransformer with the same capacity is not only small in size compared with the ordinary transformer, but also has high efficiency, and the larger the transformer capacity, the higher the voltage This advantage is more prominent. Therefore, with the development of the power system, the improvement of the voltage level and the increase of the transmission capacity, the self-lotus transformer has been widely used due to its large capacity, low loss and low cost.