Tuesday, October 25, 2016
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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