Transformer wiring, overload capacity and other information
Wiring 1, short transformer "input" and "output" terminals with megohmmeter to test its insulation resistance with the ground. 1000V megohmmeter measurement, the resistance value is greater than 2M ohms.
2, transformer input, output power line cross-section wiring should meet the requirements of the size of the current value; in accordance with the 2-2.5A/min2 current density configuration is appropriate.
3, input, output three-phase power line should be according to the transformer terminal board bus color yellow, green, red were connected to the A-phase, B-phase, C-phase, neutral zero line should be connected with the transformer voltage neutral zero line, ground line and transformer shell (such as transformer chassis should be connected with the box ground symbol corresponding to the) Check the input and output lines. Confirm the correctness.
4, the first no-load energized, observe the test input and output voltages meet the requirements. At the same time, observe whether there are abnormal phenomena inside the machine, such as abnormal noise, fire, odor, etc. If there is any abnormality, please disconnect the input power immediately.
5, when the no-load test is completed and normal, before accessing the load. Overload capacity of dry-type transformer overload capacity and the ambient temperature, overload before the load (starting load), transformer insulation heat dissipation and heat time constant, etc., if necessary, can be obtained from the manufacturer of dry-type transformer overload curve. How to utilize its overload capacity? There are two points for reference: (1) choose to calculate the transformer capacity can be appropriately reduced: give full consideration to the possibility of some steel rolling, welding and other equipment short-term impact overload - try to use the strong overload capacity of dry-type transformer and reduce the transformer capacity; for some uneven load places, such as for night lighting and other major residential areas, cultural and recreational facilities, as well as air-conditioning and daytime lighting of the shopping malls and so on, you can make full use of its overload capacity, appropriate overload reduction. Make full use of its overload capacity, reduce the transformer capacity appropriately, so that the main operating time in full load or short-time overload. (2) can reduce the standby capacity or number of units: in some places, the transformer's standby coefficient requirements are higher, so that the project selection of transformer capacity, number of units. And the use of dry variable overload capacity, in consideration of its spare capacity can be compressed; in determining the number of spare units can also be reduced. Transformer in overload operation, must pay attention to monitor its operating temperature: if the temperature rises up to 155 ℃ (there is an alarm issued) that should be taken to reduce the load measures (subtract some minor loads), in order to ensure that the main load of the safety of power supply.
The safe operation and service life of the selected dry-type transformer depends to a large extent on the safety and reliability of the insulation of the transformer windings. Winding temperature exceeds the insulation tolerance temperature so that insulation damage, is one of the main reasons that lead to the transformer can not work properly, so the transformer's operating temperature monitoring and alarm control is very important. (1) Fan automatic control: through the pre-embedded in the low-voltage winding in the hottest place of the Pt100 thermal thermistor temperature measurement resistance to measure the temperature signal. Transformer load increases, running temperature rises, when the winding temperature reaches 110℃, the system automatically starts fan cooling; when the winding temperature is as low as 90℃, the system automatically stops the fan. (2) over-temperature alarm, trip: through the buried in the low-voltage winding PTC non-linear thermal temperature resistance collection winding or core temperature signal. When the transformer winding temperature continues to rise, if it reaches 155℃, the system outputs over-temperature alarm signal; if the temperature continues to rise up to 170℃, the transformer can't continue to run, and it must deliver over-temperature trip signal to the secondary protection circuit, which should make the transformer trip quickly. (3)Temperature display system: through the pre-embedded Pt100 thermistor in the low-voltage winding to measure the temperature change value, directly display the temperature of each phase of the winding (three-phase inspection and maximum value display, and can record the highest temperature in the history), the maximum temperature can be output in 4-20mA analog output, if you need to transmit to the remote (the distance can be up to 1200m) computer, you can add a computer interface, 1 transmitter, up to 31 transformers can be monitored at the same time. One transmitter can monitor up to 31 transformers at the same time. The over-temperature alarm and tripping of the system can also be activated by a Pt100 thermal sensing resistance signal, which further improves the reliability of the temperature control and protection system.
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