Transformer short-circuit impedance is big good, or small good? The same capacity, voltage ... solution
Transformer impedance depends on the size of many factors: 1 circuit breaker breaking capacity. Transformer below the power distribution board in a variety of electrical equipment has parameters, you should calculate the short-circuit current according to the impedance of the transformer to verify that these electrical equipment can meet the requirements, the same capacity and variable ratio of the transformer, the impedance of small short-circuit current, Large short-circuit current is small; 2 transformer connected to the large-capacity motor starting voltage. If the transformer load capacity close to the transformer capacity of 1/4 of the motor, should pay attention to check its starting voltage to meet the motor terminal voltage above 70% of the rated voltage. Impedance of the transformer itself is also a large pressure drop, more difficult to meet the requirements; small impedance transformer for the start of the pressure drop better performance; because you do not know how much the transformer capacity, it can not be the absolute conclusion, if the transformer capacity below 1000KVA , The above parameters in 4% and 6% or less, the choice of 4% better
Transformer rated current / short circuit impedance = transformer short-circuit current 6% short-circuit current is small, and 4% not much difference, personal point of view! Nothing can look at Guo Weiguo teacher answered the question, will certainly benefit from the.
Can not simply say big or small good because of the big, in the normal operation of the loss of certain size, in the short circuit. Short-circuit current will be great, less investment protection equipment corresponding to the requirements of the money so much to be more economic comparison Caixing!
Can not be generalized, the choice of different transformers, impedance voltage is not the same; national transformer standard series, the general 10KV distribution transformer impedance of more than 5%, 35KV transformer impedance of more than 8%, 110KV transformer impedance In the 10% or so, the greater the capacity, the greater the impedance; transformer impedance increases, you can effectively reduce the size of short-circuit current, so in high voltage, high-capacity transformers, multi-purpose high-impedance or series reactor To reduce the short-circuit current, or some equipment is not a good choice; but the transformer impedance increases, the transformer will increase the volume, material consumption increases, the transformer running loss increases, but also to reduce the transformer secondary voltage, Is the transformer overload, the voltage will quickly decline, in case of short circuit conditions, may cause other equipment, low voltage action; under normal circumstances, or use the standard design of the transformer products, unless the special needs, do not use non-standard products, or in the Transformer side by side, selection, testing, maintenance, replacement will cause additional trouble.
