The primary and secondary coils of ordinary transformer are concentrically sleeved on an iron core column, with low-voltage winding inside and high-voltage winding outside. (the primary and secondary coils of the welding machine transformer are respectively installed on two iron core columns)
When the transformer operates with load, when the secondary side current increases, the transformer must maintain the main flux in the iron core unchanged, and the primary side current must also increase accordingly to balance the secondary side current.
Secondary active power of transformer generally = rated capacity of transformer (kVA) & times; 0.8 (transformer power factor) = kW.
. power transformers mainly include:
A. Moisture absorber (silica gel cylinder): silica gel is installed inside, the insulating oil in the oil conservator (conservator) is connected with the atmosphere through the moisture absorber, and the desiccant absorbs moisture and impurities in the air to maintain good insulation performance of the internal winding of the transformer; Silica gel discoloration and deterioration are easy to cause blockage.
B. Oil level gauge: it reflects the oil level of the transformer, which is generally about 20O. If it is too high, drain the oil, and if it is too low, add oil; In winter, when the temperature is low and the load is light, the oil level changes little or decreases slightly; In summer, when the load is heavy, the oil temperature rises and the oil level rises slightly; Both are normal.
C. Conservator: adjust the oil volume of the oil tank to prevent the transformer oil from being oxidized too quickly, and there is a refueling hole on the upper part.
D. Explosion proof pipe: to prevent explosion hazard caused by sudden accident to the pressure accumulation in the oil tank.
E. Signal thermometer: monitor the operating temperature of transformer and send signal. It indicates the upper oil temperature of the transformer, and the transformer coil temperature is 10 higher than the upper oil temperature. The national standard stipulates that the limit working temperature of transformer winding is 105oC; (i.e. when the ambient temperature is 40oC), the upper temperature shall not exceed 95oc, and it is generally appropriate to set the monitoring temperature (upper oil temperature) at 85oc or below.
F. Tap changer: change the voltage ratio by changing the tap of high voltage winding and increasing or reducing the number of winding turns.
Generally, no-load voltage regulation is adopted for the transformer, which needs to be powered off: normally divided into three gears I, II and III 5%, 0% and - 5% (10.5kv, 10kV and 0.95kv for the primary and 380V, 400V and 420v for the secondary). It is generally placed in gear II when leaving the factory.
G. Gas signal relay: (gas relay) light gas and heavy gas signal protection. The upper contact is light gas signal, which generally acts on signal alarm to indicate abnormal operation of transformer; The lower contact is heavy gas signal, which will trip, drop card and alarm the circuit breaker at the same time when sending the signal after action; Generally, if the gas relay is filled with oil, there is no gas. When there is gas in the oil tank, it will enter the gas relay. When it reaches a certain degree, the gas will squeeze out the oil storage to make the contact act; Open the outer cover of the gas relay, there are two adjusting rods on the top, and unscrew one of the caps to release the gas in the relay; The other adjusting lever is the protection action test button; Wear insulating gloves and emphasize safety during live operation.
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