Hello, I'm new to electronics and I would like to know how is the current affected by a step-up or step down transformer. EX: Lets say you have a pure AC wave (60Hz , 25vac, 5A) hooked up to a 1:4 power transformer with a current rating of 10A, What will the voltage and current be and why? Thank you!
If you assume no losses, the power remains constant. If the voltage is stepped up, the current is stepped down in the same ratio. The input current will depend on the output current drawn by the load. With a transformer stepping up 1:4, 25 volts becomes 100 volts and the current is determined by the resistance of the load. If you assume it to be 100 ohms, for example, the current will be 1 amp. This is reflected as a current of 4 amps at the input.
ok, so if you use the equation Fma you can isolate the force on the circuit by the power transformer. !st) F60*2pi3456 2nd) you plug it into the charge formula and get 32.086C, which is your answer.
Given: Primary Voltage (Vp) 25 Volts Primary current (Ip) 5 Amps Turns ratio 1 :4 Calculated: Secondary Voltage (Vs) (Vp)*(turns ratio) (25V)*(4) 100 Volts Secondary current (Is) (Ip)/(turns ratio) (5A)/(4) 1.25 Amps Why? Because the turns ratio steps up the Voltage by a factor of 4. The resistance connected to the secondary is reflected back into the primary at a value such that (Vp)*(Ip) (Vs)*(Is). (25V)*(5A) (100V)*(1.25A). In this example the load resistance was 100V/1.25A 80 Ohms. But this 80 Ohms is reflected back in to the primary as 25V/5 5 Ohms. If no losses a transformer's resistance ratio always equals the turns ratio squared. Thus in this example; (80 Ohms)/(5 Ohms) (4^2). The primary current is always determined by the secondary current which is determined by the load impedance. But in this example the primary current (5A) was given and it was necessary to use the turns ratio to calculate the necessary secondary current that determined the 5A primary current. Additional comment: Hang in there Dr Jim. I was unable to follow your explanations in this particular problem but I am sure that every thing is going to be all right in the long haul of things. After all there are other things in life besides transformers.
