Difference Between Rectifier Transformer and Power Transformer

Overview of rectifier transformerRectifier transformer is the power transformer of rectifier equipment. The characteristic of rectifier equipment is that the original side inputs AC, while the auxiliary side outputs DC after passing through rectifier elements. Converter is the general name of three working modes: rectifier, countercurrent and frequency conversion. Rectifier is the most widely used one. The transformer used as the power supply of rectifier is called rectifier transformer. Most industrial rectifier DC power supplies are obtained from AC power grid through rectifier transformer and rectifier equipment.Rectifier transformers are widely used in lighting, machine tool electrical appliances, mechanical and electronic equipment, medical equipment, rectifier devices, etc. The product performance can meet various special requirements of users.

Overview of power transformer

Power transformer is a static electrical equipment, which is used to change the AC voltage (current) of a certain value into another voltage (current) with the same frequency or several different values. When the primary winding is connected with AC, alternating magnetic flux is generated. The alternating magnetic flux induces AC electromotive force in the secondary winding through the magnetic conduction of the iron core. The secondary induced electromotive force is related to the number of turns of the primary and secondary windings, that is, the voltage is directly proportional to the number of turns. The main function is to transmit electric energy. Therefore, the rated capacity is its main parameter. Rated capacity is a customary value of power, which represents the size of transmitted electric energy, expressed in KVA or MVA. When the rated voltage is applied to the transformer, the rated current that does not exceed the temperature rise limit under specified conditions shall be determined according to it. The more energy-saving power transformer is amorphous alloy core distribution transformer. Its biggest advantage is that the no-load loss value is very low. Whether the no-load loss can be ensured is the core problem to be considered in the whole design process. When arranging the product structure, in addition to considering that the amorphous alloy core itself is not affected by external forces, the characteristic parameters of the amorphous alloy must be accurately and reasonably selected in the calculation.

The differences between rectifier transformer and ordinary power transformer are as follows:1. The current waveform of rectifier transformer is not sine wave. Since each arm of the rectifier turns on in the same cycle, and the current waveform flowing through the rectifier arm is an intermittent approximate rectangular wave, the current waveform in each phase winding of the rectifier transformer is not a sine wave.2. The DC voltage output by the rectifier circuit is not pure DC, and its waveform is pulsating in a certain program, with AC components. Obviously, the more the number of phases, the smaller the pulsation of DC voltage. Generally, the number of phases of the rectifier circuit in practical application can not exceed 12 phases at most. In order to reduce the pulsation of DC voltage, filter reactors and shunt capacitors are connected in series in the rectifier circuit, so that the rectified voltage can be close to pure DC.

3. In the three-phase rectifier circuit, the utilization coefficient of the secondary winding is k2-0.67 of the three-phase half wave; The K2 of six phase half wave is not high, and the utilization coefficient of transformer is directly related to its connection mode. According to the requirements of rectifier device, there are many connections on the secondary side of rectifier transformer. However, in order to improve the utilization coefficient of transformer, three-phase bridge and double anti star rectifier circuit with balanced reactor should be used as far as possible.4. All rectifier transformers actually have leakage reactance. In the process of rectification, when one anode is rectified and another anode is replaced for rectification, the change of anode current will not change suddenly, but one anode current will slowly weaken and the other anode current will slowly increase, resulting in the simultaneous rectification of two anodes, that is, the so-called overlap phenomenon. When there is overlap, i The values of secondary current and rectified DC voltage will change.5. The impedance of rectifier transformer is larger than that of ordinary power transformer. Rectifier transformer often has large secondary current and low voltage. Therefore, when the rectifier breaks down, a large current will flow through the transformer winding and produce much larger electric power than ordinary transformer. In order to effectively limit the short-circuit current, the impedance of the transformer is designed to be larger, and the mechanical strength of its winding iron core and other structures should be correspondingly enhanced, so its shape is short and fat.

6. Rectifier transformer has large leakage reactance voltage drop and soft output characteristics, so it has special winding connection group and external compensation device.7. The insulation strength and insulation thickness of rectifier transformer are greater than those of power transformer with the same voltage grade and capacity.