Differences Between Instrument and Power Transformers


In this article differences between power transformer and instrument transformer are discussed.Current transformer and Potential transformers come under instrument transformers.


Differences Between Instrument and Power Transformers


Power Transformers Instrument Transformers
1. Mainly used to change voltage levels in
a power system.
1. Mainly used to extend the ranges of the
instruments while measuring parameters like
voltage,current,power etc.
2. They are required to transform huge amount
of power to the load.
2. They are required to transform very small power
as their loads are generally delicate moving elements
of the instruments.
3. They can be used to step up or step down the
voltage.
3. They are basically step down transformers and
used along with devices such as protective
relays,indicators etc.
4. The exciting current is a small fraction of the
secondary winding of load current.
4. As the load it self is small, the exciting current is
of the order of the secondary winding.
5. The cost is main consideration in the design
while efficiency and regulations are secondary
considerations.
5. Accuracy is the main consideration while designing
to keep ratio and phase angle errors minimum.
Cost is the second consideration.
6. As they handle large power, the heat
dissipation is the major consideration and
cooling method is necessary.
6. The power output is very small as loads are light.
Hence heating is not severe.
7. The limitation on the load is due to temperature
issue.
7. Accuracy is the main load limitation factor and not
the temperature rise.
8. Example : Distribution transformer used in
transmission.
8. Example : Current transformer and Potential
transformer

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