Vaibhav Singh(130950111013) EC (2nd Year 3rd Sem) Subject :- Electrical Machines(2131005)

Special Transformer Current Transformer ( C.T. ) Potential Transformer ( P.T. ) Pulse Transformer Audio Frequency Transformer ( A.F. ) Radio Frequency Transformer ( R.F. )

Current Transformer A current transformer is nothing but a coil wound on a toroidal core.  Current transformer isolates the measuring instruments from what may be very high voltage in the monitored circuit. Current transformers are commonly used in metering and protective relays in the electrical power industry.

Construction of C.T. C.T. has a primary coil which has a primary coil of one or more turns. The primary of C.T. carries the large current I1 which is to be measured. The secondary of a C.T. is made up of large number of turns, It is a wound on a core.

Potential Transformer The potential transformer is another type of instrumentation transformer. To measure high voltage, the potential transformer is connected across high voltage terminals and voltmeter is connected on law voltage side. A potential transformer is an ordinary two winding with high turns ratio, designed for low current carrying capacity. The turns ratio is adjusted in such a way that the secondary voltage 110v irrespective of the primary voltage.

Applications of C.T & P.T. Measurment of power. Measurment of energy. Measurment of current in single phase & three phase system. Measurment of voltage in single phase & three phase system.

Pulse Transformer Hence a special transformer called pulse transformer is designed to couple pulses from primary to the load connected to the secondary. Pulse transformers are used for coupling pulses from a low power digital circuit to a high power SCR or triac circuit maintaining the isolation between them. Pulse transformers are small in size. The capacitance between the windings is small. It has a high voltage insulation between its windings and ground.

Audio Frequency Transformers The audio frequency transformers are specifically designed for use in audio circuits. They oprate in the audio frequency range (20Hz to 20kHz) A.F. transformers were originally designed for connecting different telephone systems to each other keeping their respective power supplies isolated. The construction of A.F. transformer is same as that of a normal transformer. These are iron core transformers.

Application of A.F. AF amplifiers. Radio, TV receivers. Music systems. Impeance matching Mixing consoles Professional audio systems.

Radio Frequency Transformers These are specially designed transformers used in the radio frequency (RF) range. It is not possible to use steel laminated core for RF transformers. These are used mainly in communication circuits and generally employ tuned secondary windings. The calculations required in the design of such transformers are involved, particularly as regards. Reference should be made to the literature for design details, e.g. Radio Designer’s Handbook.

Application of R.F. R.F. amplifiers. Radio, TV receivers. Communication circuits.

Thank You…..