what we use a step up transformer ?
why we use step down transformer?
what are their losses ?

 

We use Step up transformer for stepping up voltage (say 600 v to 120 V).
We use Step down transformer for stepping down voltage (say 120 v to 600 V).
As for losses, do you mean the types of losses in transformers ?
Losses can be heat losses, eddy current losses, hysterisis losses, etc.

 

what we use a step up transformer ?
why we use step down transformer?
what are their losses ?

Why didn't you look in Google?

 

someone told me that step up tranformergive us a low current and also gives some losses after that we use step down transfomer its that true?

 

someone told me that step up tranformergive us a low current and also gives some losses after that we use step down transfomer its that true?

In a power staton a step up transformer is used to convert the relatively low voltage from the generators to a high voltage (often in the neighborhood of several hundred thousand volts) for transmission to the place it is to be used since, for a given power, a higher voltage means less current and thus less loses in the power line wire resistance and allowing the use of smaller wire. At the end of the line the voltage is stepped down to a lower voltage (perhaps a few thousand volts) for transmission over city power lines to reduce insulation requirements of the wire. Then at the home this voltage is further reduced for safety to the typical 120/240V. All these transformers do have some inefficiency (a few percent) and waste a small amount of the power, but there is still a huge saving in wire cost over not doing the voltage changes.

The inability of being able to readily change the voltage of DC power is the main reason the DC that Edison used in his early power plants was replaced by the AC that Tesla advocated.

 

thanks alot