Current Transformers with mA output.

With the advent of digital relays, earlier secondary outputs such as 5A and 1A were considered unnecessary for some applications.  Accordingly, current transformers with lower outputs were designed.  These outputs, usually in the mA range, are constructed by increasing the no of turns in the secondary. 

Since, these current transformers have a large number of secondary turns as compared with normal CTs, special voltage suppression devices are incorporated in order to limit the voltage to a safe value if the current transformer is accidentally open circuited. 

These current transformers have high accuracy.  They are also cheaper in cost and smaller in size.  The disadvantages of these Current transformers are that they poor phase shift performance and can perform only with specific dimensions of wires. 

mA Current Transformers are different from Current Transducers which employ current sensors to sense current and generate a 4..20 mA