Step-down transformer, voltage?

Question

A step-down transformer connected to a 120V electric generator has 30 loops on the primary for each loop in the secondary.

A) What is the voltage of the secondary?

B) If the transformer has a 90 A current in the primary, whats the current in the secondary?

C) What is the power input and output?

Please show equations as well, Thanks!

Answer 1

A.  Four volts.

B.  It can be as much as 30 x 90 = 2700 amperes.  That is a LOT of current.

C. 10800 watts.

First response is correct except for a minor arithmetic error in part C.

Answer 2

The voltage ratio is equal to the turns ratio (1/30).

120 x 1/30 = 4

The secondary voltage is 4 Volts.

If the transformer is 100%  efficient, the power in is equal to the power out. Power watts = volts x amps.

120 x 90 = 10800 watts

The output current  = watts/volts

10800/4 = 2700 amperes

Answer 3

The ratio of the number of turns is 1 over 30.

A) V2 = (N2 / N1) x V1 = 120 V / 30 = 4.0 V

B) I1V1 = I2V2 → I2 = (I1V1) / V2 = (90 A x 120 V) / 4.0 V = 2700 A

C) P = IV → P (input) = 90 A x 120 V = 11,000 W and P (output) = 2700 A x 4.0 V = 11,000 W

Answer 4

The ratio of the number of turns is 1 over 30.

A) V2 = (N2 / N1) x V1 = 120 V / 30 = 4.0 V

B) I1V1 = I2V2 → I2 = (I1V1) / V2 = (90 A x 120 V) / 4.0 V = 2700 A

C) Power = Current x Voltage

Input Power = 90 A x 120 V = 10,800 W

Output Power = 2700 A x 4.0 V = 10,800 W

As you can see, voltage and current is transformed, but the power remains the same.