First, the transformer related terms
The basic working principle of the transformer is the principle of electromagnetic induction. It is an electrical appliance that converts one type of voltage, current, and phase number of alternating current energy into another type of voltage, current, and phase number of alternating current energy.
Rated capacity: Woodworking engraving machine indicates the output capacity of the transformer under rated conditions of use, expressed as apparent power VA.
Rated voltage: indicates the rated voltage value of each winding of the transformer at no load, expressed in V.
Rated current: Indicates the current value of each winding of the transformer under rated load, denoted by A.
Connection group label: represents the connection method and phase angle relationship symbol of each winding of the transformer. Such as Y/Y (star connection)
Second, the classification and structure of the transformer
1. Classification: According to the number of phases, it can be divided into single phase and three phase; according to the number of windings, it is divided into single ring type (autotransformer), double coil type and multi-turn type (machine tool control transformer, power transformer).
2. Core structure: The transformer consists of iron core and wire package. The transformer cores are generally stacked in an overlapping manner, and the laminated shapes shown in the following figures are generally used in the power transformer and the control transformer.
Mountain type or E type
3, winding structure: there are two types of concentric and overlapping.
Third, the transformer allows the way of operation
Rated operation mode: Operate according to the relevant technical data specified on the nameplate under the specified cooling conditions.
Permissible voltage variation: During the operation of the transformer, the grid voltage has a certain change due to the change of day and night load, and the transformer side voltage also has a certain variation. When the primary side voltage applied to the transformer is equal to or lower than the rated voltage of the primary side coil of the transformer, no effect will occur. If it is greater than the rated voltage, the side should not exceed the allowable value. Therefore, both the national standard and the operating procedures stipulate that the rated maximum capacity can be operated when the maximum voltage does not exceed 5% of the corresponding tap voltage.
Load capacity of the transformer: The maximum capacity that the transformer can output in a relatively short period of time without damaging its normal use and increasing the natural loss of insulation. The multiple of overload and the time of operation under overload should be kept at Within a certain limit.
Parallel operation of transformers: The main problem that arises when operating in parallel is how to ensure an even distribution of the load between the transformers after parallel connection. When the transformer is operated in parallel, several conditions must be met. One is that the voltage on the high voltage and low voltage side of the transformer must be equal. The second is that the short circuit voltages of all transformers are equal. The third is when the three phase transformers are operated in parallel. The numbers must be the same.
Fourth, the selection of transformers in the engraving machine
1. Determination of capacity: According to the power of the load connected to the transformer, generally followed by the drive and the motor, the voltage is provided according to the drive, and the current of the drive is determined according to the motor. After the two data are determined, plus 15~ The 20% wealth is the total capacity of the transformer.
2, the number of output groups and one can support several drivers: the number of output groups of the transformer can be more than one set, as long as the capacity can be satisfied, it can achieve multiple inputs and multiple outputs. For example, 220V in, two groups of 90V out or 220V in, four sets of 75V out and so on. Determined by the motor and drive that the machine is carrying.
3. Voltage and current: The voltage is the voltage that provides the drive, and the transformer is the voltage of the AC. If it is necessary to implement DC, a rectifying device can be added to achieve AC to DC conversion. The current is the key to the operation. It is determined by the current required by the motor that is carried. When the transformer is turned to the transformer, the current needs to be increased.
4, servo transformer selection needs to pay attention to several problems: First, according to the servo motor and the input voltage of the system to determine the output voltage of the transformer, the second capacity is determined according to the power of the servo motor, the three connections The group is determined according to the requirements of the servo system, such as Y/Y, Y/Y0 and so on. The output voltage of the servo transformer is determined based on the voltage of the servo.
V. Reasonable and unreasonable problems that need attention or problems
1. Isolation of transformer: At present, the LBK5 series and LSG three-phase series isolation transformers produced by Lampu Electric are isolation transformers, which are isolated between the primary and secondary, and each of the secondary windings. As shown in Figure 1, the two sets of engraving machines have three-axis directions, insufficient precision, or strikes in the XYZ isometric. The main reason is that there is no isolation in the control system and interference from the transformer.
2. The number of output groups or a few drives: Generally, most manufacturers choose to use one input and one output. Most of the considerations are that different time work can save costs. Once there is simultaneous work, there will be insufficient precision or depth. There will be some interference between them, and the heat is serious, and the transformer insulation aging is accelerated. The life surface and the safety factor are greatly reduced. Because the current is not properly distributed to each motor or drive when it is distributed, some of the load requirements will be met, and some will have a load of 80-90% or even lower. It is reasonable to allocate reasonable data according to the actual needs of each group, and each group is isolated, which may avoid the occurrence of after-sales or transformer damage that should occur. According to the driving needs of the engraving machine, a lot of groups can be realized. At present, there are one for two, one for three, one for four, one for six, etc., according to your needs, we can design and produce according to your needs. Transformers made according to the needs of customers fully meet the various working needs of the machine, without any damage and interference, almost zero after repair and retail.
3, E type (square type) and other differences: the so-called "transformer" is the "transformer" that we are talking about is the "transformer" designed by the principle of electromagnetic induction. Other components that realize voltage changes cannot be called transformers. Such as switching power supplies and three-phase electronic transformers on the market. The principle of the three-phase electronic transformer is made out of silicon, and everyone can achieve it. Just like the engraving machine factory makes the rectification version itself, there is no need to buy it separately. Approximate switching power supply structure can achieve voltage conversion, but the principle of "transformer" is very different. The main advantage is that the price is cheap, the service life and reliability are far lower than expected, and the traditional transformer is basically not damaged, the service life is long and safe, and it can be used by random machines or machine tools for decades, even the machine overhauls the transformer. Still intact.
