High voltage transformers are mainly used to transform voltages from one phase configuration to another. They are normally used to shift from a higher phase to a lower one. They may include components for electrical isolation and power distribution.
This design of transformer relies on the concept of magnetic induction in coils, where it is possible to alter the current or voltage levels. These transformers are mainly a single-phased core type. They can also be oil-immersed. In this article, we will see together what high voltage transformers are and how they work.
How do high voltage transformers work?
Bakelite sheets may be applied to separate high and tension windings. The high voltage machines used for high voltage cable testing require the supply of enough electric current. This produces a lot of heat, meaning that their cooling system should be very carefully designed.
For insulator testing, the current should be minimized. However, upon the breaking of the insulator, a huge current will flow into the transformer. In order to curb this hazard, a high-resistance resistor is connected in series to the transformer.
High voltage transformers used to test insulators do not require a high kVA rating as the process does not need high currents.
How should you regulate the voltage?
You should avoid the stream on the high power strength side of the generator. The voltage regulation should be smooth too in order to attain the most accurate voltage measurement. You would also be better to keep away from immediate changes in voltage during testing.
A voltage regulator must not alter the voltage wave while testing the transformer. The out-turn voltage of a massive voltage transformer is controlled by altering the input voltage on the primary side.
The disparity of input voltage on the main side can be obtained through the following methods:
- Variation of the alternator electric field current.
- Adding some resistance in the distribution circuit from the alternator.
- Using an induction regulator.
- Using a tapped transformer.
How does an alternator with electric-field current work?
This method can be truly effective if only one alternator is used for supplying power to the HV transformer. An alternator will give a sinusoidal signal form of voltage with no load.
This waveform should not be disarranged under load conditions. This can be achieved by increasing the air space between the rotor and the stator. In order to regulate the voltage, no resistivity is required to be in connection to the primary transformer in series. So the waveform distortion voltage will disappear thanks to the resistance inserted.
With this strategy, we can achieve zero voltage by offsetting the residual magnetism of field and severing field current.
How should you insert impendance in the distribution circuit?
This method is mainly effective when there is no room for using another alternator for massive voltage testing. A high voltage transformer is given power form the A/C distribution mains while testing small equipment is done.
The disparity of the supply voltage to the transformer is attained by inserting impedance in series with the AC distribution. The most effective way of achieving smooth regulation of the voltage distributed to the main transformer is by introducing a sliding resistance.
The resistance could also be connected so that a voltage divider is placed across the primary supply to distribute a changing voltage to the high voltage transformer.
How does an induction regulator work?
An induction regulator control proves perfect for most of the power ranges. It can easily be applied to all power factors and loads. With this method, we can achieve from a trouble-free voltage regulation to full range from zero.
An induction regulator is basically a variable transformer. If you alter the primary turns of this variable transformer, you are going to attain its secondary voltage. The variations will be achieved by turning a knob that is at the transformer.
Here the number of turns in both secondary and primary windings is equal. But if you rotate the knob on the transformer, the total number of turns found in the primary changes. For this reason, the turns ratio is also different, and so we can observe a variable secondary voltage.
During the making of this high voltage transformer, it is vital that the winding of the transformer on the side of the rotor is sufficiently engineered so that it does not change the actual waveform of the voltage under test. This method is categorically suitable for high voltage transformers that are used to test power cables. This is because its slowly increasing voltage variation at loads of any size is an advantage for such a job. If you are looking for the best high voltage transformers, we highly suggest you contact Guangdong Sihui. They produce and sell many kind of products, including 0.72-1000kV current transformers, voltage transformers, 0.72-40.5kV dry-type power transformers, reactors, and many more.
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