What type of transformers are current transformers classified as?

Current transformers are specifically designed to measure the current flowing through a conductor by producing a secondary current that is proportional to the primary current. They essentially act as a means to step down the current to a manageable level for measurement and protection purposes.

The correct classification relates to their operational intent and functional design. Current transformers are not meant to step up voltage; rather, they are used primarily for current measurement and do not change voltage levels in the same manner that a voltage step-up transformer would. Therefore, A is not an accurate classification of current transformers.

The other classifications listed do not accurately apply to current transformers. K-type transformers are a specific type of transformer used in certain applications, but they don't encompass the general function of current transformers. High power factor transformers typically refer to transformers designed to operate efficiently at high power factors, which is not relevant to the operation of current transformers. Lastly, current step-up transformers would imply that these devices increase the current, which contradicts their actual functioning as they lower the current for safe measurement.