Characteristics of Surge Generators for Transformer Testing

The requirements and limitations of surge generators for transformer testing can be summed up as follows: The voltage that can be obtained is, in the first place, largely determined by the capacity of the surge generator when the capacity of the transformer is great. If a wave is desired without superimposed oscillations, it is necessary to insert resistance within the generator. The front of the surge then depends upon the inductance of the generator and the capacity of the transformer. This is a matter inherent to all surge generator test circuits. Thus, in general, waves of very steep front cannot be obtained with large transformers. Further, the inserted resistance also limits the voltage by an amount dependent on the proportion of this resistance to the load resistance. For transformers of low inductance, the length of the wave obtained is largely determined by the capacity of the surge generator. This results in a requirement of large generator capacity if very long waves are to be produced. If the lead between the transformer and generator is appreciably long, other oscillations will be set up which are highly damped but are appreciable at the generator end. These oscillations occur on the front of the wave only, and will be prominent when measurements are taken at the surge generator.