Rectifier common temperature rise is too high fault and its reason
Rectifier in the course of the operation, the loss mainly includes the core of the hysteresis and eddy current loss, winding resistance loss. These losses produce a lot of heat, under normal circumstances, these heat through the cooling device to the outside world, while to a certain extent, the rectifier temperature rise. After a certain period of time, the rectifier should reach a stable temperature rise. If the temperature rise is too high or the temperature rise too fast, or with the same type of load rectifier compared to its temperature rise was too high, it should be considered a failure. Causing the rectifier temperature rise is too high reasons, common mainly in the following categories:
1. Core local short circuit. 2. Poor grounding of the core. 3. Iron yoke screw ground. 4. The power supply voltage is too high. 5 lead part of the poor contact, loose, burned and so on. 6. The tap changer is faulty. 7. Coil manufacturing and maintenance caused by poor quality. 8. Core pile around the burr, the gap caused by uneven. 9. Rectifier load is high. 10. Rectifier a second connection failed or poor contact caused.
Third, the rectifier common output voltage abnormalities and their causes In normal circumstances, the rectifier output voltage should be kept within a range. Voltage is low or high are fault phenomenon, should be promptly excluded. First check the power supply voltage to see if it is due to abnormal supply voltage. If the supply voltage is high, it can be measured by the transformer. In addition to power reasons, the common causes of failure are the following:
1. Winding turns between short turns. This kind of fault is caused by overload or insulation of rectifier. When there is a short circuit, the rectifier will have abnormal output voltage, sometimes overheating and abnormal sound.
2 The tap position is incorrect. The on-load tap-changer is used to adjust the voltage, if the gear is not correct, can not match the actual supply voltage, will cause the output voltage is too high or too low.
3. Three-phase load imbalance caused. If the rectifier secondary three-phase imbalance, will cause the rectifier three-phase voltage changes, the output voltage is abnormal. Serious, the phase voltage increases 1.732 times.
4. High pressure side appears phase. High voltage side of the lack of phase, will cause low-voltage side of the output voltage of the serious imbalance, and even cause damage to low-voltage equipment. There are many reasons for the lack of high pressure, but are generally due to maintenance is not in place and other causes of wiring part of the burn or the old line caused by failure.
Insulation measurement. Mainly used to determine the insulation of the winding, a relatively simple and effective method. Insulation resistance is usually measured using insulation resistance table, 3KV above the high-voltage rectifier generally use 2500V insulation resistance table. Measurements: Measure the insulation resistance of the windings. Should measure the high voltage winding to ground, low voltage winding to ground, high voltage winding on the low voltage winding three, here "ground" refers to the rectifier metal shell. ② DC resistance measurement. When the rectifier in the short-circuit impact, often may cause distortion of the winding, the other rectifier winding insulation damage, will cause inter-turn short circuit, or even phase short circuit. When the winding is faulty, the resistance between turns is changed due to the change of the inter-turn distance due to the whole or local stretching and compression. When measuring, the DC resistance of the high and low voltage winding of the rectifier should be measured separately. According to the relevant provisions of the manufacture of electric power rectifier, 630KVA above the rectifier phase winding DC resistance should not be greater than the difference between the three-phase average of 2%, 630KVA the following rectifier, phase difference should not be greater than the three-phase average of 4% The difference is not greater than 2% of the average of the three phases. ③ absorption ratio measurement. Rectifier winding insulation and moisture conditions can be determined by measuring the absorption ratio.