The original and secondary coils of the ordinary transformer are concentrically placed on a core leg, which is a low voltage winding and a high voltage winding. When the transformer is running with load, when the secondary current increases, the transformer must maintain the main magnetic flux in the iron core, and the primary current must also increase accordingly to reach the balanced secondary current.
The secondary active power of the transformer is generally = transformer rated capacity (KVA) × 0.8 (transformer power factor) = KW.
Power transformers mainly include:
A, moisture absorber (silicone tube): contains silica gel, the insulating oil in the oil conservator (oil pillow) communicates with the atmosphere through the moisture absorber, the desiccant absorbs moisture and impurities in the air to keep the internal winding of the transformer good. Insulation performance; discoloration of silica gel, deterioration and easy to cause blockage.
B. Oil level meter: It reflects the oil level status of the transformer, generally around +20O. If it is too high, it needs to drain oil. If it is too low, it will refuel. When the temperature is low in winter, the oil level changes little when the load is light, or the oil level drops slightly. In summer, when the load is heavy, the oil temperature rises and the oil level rises slightly; both are normal.
C. Oil pillow: adjust the oil volume of the fuel tank to prevent the transformer oil from oxidizing excessively. The upper part has oiling holes.
D. Explosion-proof pipe: Prevent sudden accidents from causing explosion hazard due to pressure accumulation in the fuel tank.
E. Signal thermometer: Monitor the operating temperature of the transformer and send a signal. Indicates the upper oil temperature of the transformer, and the transformer coil temperature is 10 °C higher than the upper oil temperature. The national standard stipulates that the ultimate operating temperature of the transformer winding is 105 OC; (ie, when the ambient temperature is 40 OC), the upper layer temperature must not exceed 95 OC, and it is generally preferable to set the monitoring temperature (upper layer oil temperature) to 85 OC or less.
F, tap changer: change the voltage ratio by changing the high voltage winding tap to increase or decrease the number of winding turns. ∵: U1/U2=W1/W2, U1W2=U2W1, ∴: U2=U1W2/W1. Generally, the transformers are unloaded and voltage-regulated, and need to be powered off: Normally divided into I, II, III third gear +5%, 0%, -5% (one time is 10.5KV, 10KV, 0.95KV is 380V, 400V, 420V twice) ), generally placed in the II block when leaving the factory.
G, gas signal relay: (gas relay) light gas, heavy gas signal protection. The upper contact is a light gas signal, generally acting on the signal alarm to indicate that the transformer is running abnormally; the lower contact is a heavy gas signal, and the circuit is tripped, dropped, and alarmed when the signal is sent after the action; the gas relay in the general gas relay is full of oil. Gas, when there is gas in the fuel tank, it will enter the gas relay. When it reaches a certain level, the gas will squeeze out the oil to make the contact action; open the gas relay cover, there are two adjustment rods on the top, and one of the caps can be unscrewed to release the relay. The inside of the gas; the other adjustment rod is the protection action test button; the insulated gloves must be worn and the safety is emphasized.