Converter is the general term for the three working modes of rectification, countercurrent and frequency conversion, and rectification is the most widely used one. The rectifier is characterized by rectifying and filtering the input alternating current and then outputting it as direct current.
The rectifier transformer is the power transformer of the rectifier equipment. Most of the rectified DC power supply for industrial use adopts the method of rectifier transformer and rectifier equipment.
Power transformers generally refer to transformers that supply power to electric drive systems, and most of the transformers in the power grid are power transformers.
1. Function difference
The functions of the rectifier transformer: 1. It is to supply the appropriate voltage for the rectification system; 2. It is to reduce the pollution to the power grid caused by the waveform distortion caused by the rectifier transformer system.
The output of the rectifier transformer is still AC, it just provides power to the rectifier equipment. Usually, the primary side is connected in a star shape, and the secondary side is connected in an angular shape, which is used to suppress high-order harmonics.
The secondary side is connected in an angled neutral point and is not grounded. When the rectifier transformer equipment is grounded at one point, it will not cause equipment damage, and the ground fault alarm signal will be sent out through the grounding detection equipment. Shield isolation is added between primary and secondary.
Rectifier transformers are mainly used in electrolysis, smelting, excitation, transmission, cascade speed regulation, electrostatic dust removal and high-frequency welding and other fields. There is a difference in the structure. In order to make the waveform smooth, the rectifier transformer for electrolysis is made into a six-phase output, and a six-phase rectifier bridge is added outside to obtain a relatively smooth waveform.
For smelting and high-frequency welding, according to the current waveform characteristics of the thyristor rectifier circuit and the anti-harmonic requirements, the eddy current loss in the rectifier transformer winding and the stray loss in the structural parts are optimized for certain data and processes. The structure is similar.
The power transformer is usually grounded at the neutral point of the Y/Y connection (single-phase power supply). If it is used for rectification equipment, it will cause damage to the rectification equipment when a ground fault occurs. Moreover, its ability to suppress high-order harmonics generated by rectification equipment is also poor.
2. Differences in use
A transformer used as a rectifier power supply is called a rectifier transformer. Most of the rectification and DC power supplies used in industry are obtained by rectification equipment composed of rectification transformers and rectifiers from the AC grid.
In today's highly modernized world, its great use can be seen directly or indirectly in almost every field. Power transformers are mainly used in power systems, daily lighting and factory power.
The main uses of rectifier transformers are as follows: electrochemical industry; DC power supply for traction; DC power supply for transmission; DC power supply for DC transmission; DC power supply for electroplating or electrical processing; DC power supply for excitation; DC power supply for charging; DC for electrostatic dust removal power supply;
3. Output voltage difference
The difference in name: Due to the close combination with the rectifier, the output voltage of the rectifier transformer is called the valve side voltage. Its name originates from the unidirectional conductivity of the diode.
Differences in calculation methods: Due to the different waveforms of the load current of the rectifier device, the calculation method of the output current is not only very different from that of the power transformer, but also the calculation methods are different for different rectifier circuits.
4. There are differences in design and manufacturing
Due to the difference in use between the rectifier transformer and the power transformer, the design and manufacture are also very different from the power transformer:
Taking into account the working conditions of the rectifier transformer, the rectifier transformer has achieved lower current density and magnetic flux density; the impedance has also been slightly larger.
In terms of the structure of the winding, sometimes two windings are required on the valve side to supply forward and reverse transmission or forward transmission and reverse braking respectively.
When braking, the converter device is in the inverter working state; if the transformer has harmonic requirements, a shielding layer with a grounding terminal should be placed between the windings;
Strengthen the pressure plate and stays, increase the oil channel and other measures to improve the short-circuit resistance of the winding; in addition, in terms of heat dissipation, compared with the power transformer, the width considered in the design and manufacture is usually larger.
