What is the difference between rectifier transformer and power transformer?
What is a Rectifier Transformer?
Current conversion encompasses three working modes: rectification, inversion, and frequency conversion. Rectification is the most widely used. The primary characteristic of a rectifier device is that it converts input AC power into output DC power through rectification and filtering. A rectifier transformer is the power transformer used in rectifier devices. Most industrial rectified DC power supplies are obtained through rectifier transformers and rectifier devices.
What is a Power Transformer?
Power transformers typically refer to transformers that supply power to electrical drive systems. Most transformers in power grids are power transformers.
Differences Between Rectifier Transformers and Power Transformers
Functional Differences
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Functions of Rectifier Transformers:
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Provide appropriate voltage for the rectifier system.
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Reduce the pollution of the power grid by the waveform distortion caused by the rectifier system.
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The output of a rectifier transformer is still AC, solely supplying power to the rectifier device. Typically, the primary side is connected in a star configuration, and the secondary side is connected in a delta configuration to suppress higher-order harmonics. The corner neutral point of the secondary side is not grounded. When the rectifier device is grounded at one point, it does not cause equipment damage, and a ground fault alarm signal is sent through the ground detection device. Additionally, shielding isolation is added between secondary coils.
Rectifier transformers are mainly used in electrolysis, smelting, excitation, power transmission, series speed regulation, electrostatic dust removal, and high-frequency welding. Structurally, they are somewhat different. To achieve smooth waveforms, some electrolysis rectifier transformers are made with six-phase outputs, and an external six-phase rectifier bridge is added to obtain relatively smooth waveforms. According to the current waveform characteristics and anti-harmonic requirements of the thyristor rectifier circuit used in smelting and high-frequency welding, the eddy current loss in the windings and stray loss in the structural components of the rectifier transformer are optimized for specific data and processes. In fact, the overall structure is also similar.
Power transformers are usually grounded at the neutral point in a y/y connection (providing single-phase power). If used for rectifier equipment, they can damage the rectifier equipment in the event of a ground fault and have poor suppression of the higher-order harmonics generated by the rectifier equipment.
Different Uses
Transformers used as rectifier power supplies are called rectifier transformers. Most industrial rectified DC power supplies are obtained from the AC power grid through rectifier devices composed of rectifier transformers and rectifiers. In today's highly modernized society, their extensive use can be seen directly or indirectly in almost every field. Power transformers are mainly used in power systems, daily lighting, and factory electricity. The main uses of rectifier transformers are as follows:
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Electrochemical industry.
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DC power supply for traction.
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DC power supply for transmission.
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DC power supply for DC transmission.
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DC power supply for electroplating or electrical processing.
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DC power supply for excitation.
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DC power supply for charging.
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DC power supply for electrostatic precipitators.
Output Voltage Differences
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Naming Differences: Due to their close association with rectifiers, the output voltage of a rectifier transformer is called the valve side voltage, named after the unidirectional conductivity of the diode.
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Calculation Method Differences: Due to the different waveform of the rectifier load current, the calculation method for its output current differs significantly from that of power transformers and varies for different rectifier circuits.
Differences in Design and Manufacturing
Due to the different applications of rectifier transformers and power transformers, their design and manufacturing also differ significantly:
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Considering the working conditions of rectifier transformers, they achieve low current density and magnetic flux density, as well as slightly higher impedance.
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In terms of winding structure, the valve side sometimes requires two windings to supply power for forward and reverse transmission or forward transmission and reverse braking. During braking, the converter operates in an inverter state.
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If the transformer has harmonic requirements, a shielding layer with grounded terminals should be placed between the windings.
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Various measures, such as strengthening the pressure plate and bracket and expanding the oil circuit, are taken to improve the winding's short-circuit resistance.
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Additionally, regarding heat dissipation, rectifier transformers usually consider a larger margin than power transformers in their design and manufacturing.
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