Methods of secondary short circuit current control in single phase transformers

Abstract

The control of secondary current of a single phase transformer can be achieved using taps, rheostats in the secondary winding. But these lead to increase in expense as well as make the design difficult. These are effective for sensitive applications. For obtaining high current at low voltage (2-5A) at low voltage which may be used for powering small electromagnets, control of current from primary side proves to be more effective. This simply involves the principle of voltage reduction at the primary. The supply voltage is kept constant at 240V-50Hz. No intermediate transformation is required. The voltage control is achieved using a. Resistors b. Inductors (Choke) c. Capacitors Of these capacitors prove to be most efficient. This is because capacitors can provide both reduction and magnification of transformer primary voltage. Hence, both reduction and increase of the secondary current is possible. Inductors and resistors reduce primary voltage and hence secondary short circuit current. In case of capacitors, various combinations (sometimes along with resistors and inductors) are possible. In this paper various methods of secondary current control using passive elements at the primary have been presented.