Box transformer common knowledge questions, including a variety of practical knowledge of the transformer Q & A, such as the transformer for a long time in the limit temperature operation of any hazards, auto-transformer operation on which the main advantages and disadvantages of the parallel operation of the transformer conditions, This paper will answer these eleven questions common knowledge of these transformers.
(1): Transformer for a long time in the limit temperature to run what harm?
A: oil-immersed transformers are mostly A-class insulation, the maximum temperature allows heat 105 ℃, transformer winding temperature is higher than the average oil temperature 10-15 ℃, is when the operation of the upper oil temperature of 85-95 ℃ when the winding has actually reached about 105 ℃, if the long run at this extreme temperature, the winding insulation serious aging, and accelerate the deterioration of insulating oil affect the service life. (2): What are the main advantages and disadvantages of autotransformer operation?
A: The autotransformer running on the main advantages: ① less power consumption, high efficiency;
② can be made into a single large-capacity transformers;
③ in the case of the same capacity, small size, light weight, easy transportation, and save materials, low cost.
The main drawbacks: ① impedance percentage is small, so the system short-circuit current;
② low-voltage winding more easily over-voltage, so the neutral point must be directly grounded;
③ more difficult to deal with voltage regulation problem.
(3): parallel operation of the transformer What are the conditions? why?
A: The conditions of parallel operation of the transformer:
(1) All the transformers for parallel operation must be connected in the same group. Otherwise, the secondary side of the voltage difference is great, resulting in a large circulating current or even as short-circuit current, will damage the transformer; ② the primary side of the transformer voltage should be equal, secondary voltage are equal. (3) the transformer impedance voltage (short-circuit voltage) percentage should be equal, or with load after the load distribution is unreasonable. (3) the transformer voltage is not the same as the load voltage, the other side of the loop caused by overload, heat, affecting the load, and increase power loss. Because the capacity of the transformer short-circuit voltage percentage of large, small capacity of the transformer short-circuit voltage percentage is small, and the load distribution and the percentage of short-circuit voltage is inversely proportional to this will cause a large transformer distribution of the load is small, the device is not fully utilized; and small transformer load Large, easy overload, limiting the parallel operation of the transformer with load operation.
(4): a single transformer running under what circumstances the most efficient? What is the economic operation of the transformer?
A: The single transformer operating efficiency of the highest point, the condition is: when the variable loss (coil copper consumption) is equal to the same loss (core loss), the general load factor β = 0.6 <about 60% of rated load, The highest point. When several transformers run side by side, due to the transformer iron consumption is basically the same, and copper consumption changes with the load, so the need to adjust the size of the load running the number of units and capacity of the transformer, the total power loss of the transformer to a minimum, This mode of operation, known as the economic operation of the transformer.
(5): Run the duty on-load regulator, should pay attention to what the situation?
A: The attendant on-load voltage regulator, the voltage meter should be noted that the instructions are in the voltage range, the position indicator, the counter is correct, and check the gas relay and oil level oil is normal, good records. When the load is greater than 80% of rated value, prohibit the operation of on-load tap changer
(1): Transformer for a long time in the limit temperature to run what harm?
A: oil-immersed transformers are mostly A-class insulation, the maximum temperature allows heat 105 ℃, transformer winding temperature is higher than the average oil temperature 10-15 ℃, is when the operation of the upper oil temperature of 85-95 ℃ when the winding has actually reached about 105 ℃, if the long run at this extreme temperature, the winding insulation serious aging, and accelerate the deterioration of insulating oil affect the service life. (2): What are the main advantages and disadvantages of autotransformer operation?
A: The autotransformer running on the main advantages: ① less power consumption, high efficiency;
② can be made into a single large-capacity transformers;
③ in the case of the same capacity, small size, light weight, easy transportation, and save materials, low cost.
The main drawbacks: ① impedance percentage is small, so the system short-circuit current;
② low-voltage winding more easily over-voltage, so the neutral point must be directly grounded;
③ more difficult to deal with voltage regulation problem.
(3): parallel operation of the transformer What are the conditions? why?
A: The conditions of parallel operation of the transformer:
(1) All the transformers for parallel operation must be connected in the same group. Otherwise, the secondary side of the voltage difference is great, resulting in a large circulating current or even as short-circuit current, will damage the transformer; ② the primary side of the transformer voltage should be equal, secondary voltage are equal. (3) the transformer impedance voltage (short-circuit voltage) percentage should be equal, or with load after the load distribution is unreasonable. (3) the transformer voltage is not the same as the load voltage, the other side of the loop caused by overload, heat, affecting the load, and increase power loss. Because the capacity of the transformer short-circuit voltage percentage of large, small capacity of the transformer short-circuit voltage percentage is small, and the load distribution and the percentage of short-circuit voltage is inversely proportional to this will cause a large transformer distribution of the load is small, the device is not fully utilized; and small transformer load Large, easy overload, limiting the parallel operation of the transformer with load operation.
(4): a single transformer running under what circumstances the most efficient? What is the economic operation of the transformer?
A: The single transformer operating efficiency of the highest point, the condition is: when the variable loss (coil copper consumption) is equal to the same loss (core loss), the general load factor β = 0.6 <about 60% of rated load, The highest point. When several transformers run side by side, due to the transformer iron consumption is basically the same, and copper consumption changes with the load, so the need to adjust the size of the load running the number of units and capacity of the transformer, the total power loss of the transformer to a minimum, This mode of operation, known as the economic operation of the transformer.
(5): Run the duty on-load regulator, should pay attention to what the situation?
A: The attendant on-load voltage regulator, the voltage meter should be noted that the instructions are in the voltage range, the position indicator, the counter is correct, and check the gas relay and oil level oil is normal, good records. When the load is greater than 80% of rated value, prohibit the operation of on-load tap changer