How you calculate voltage in a step up transformer on ac?

Answer 1

There is no such equation, since the output of a step-down transformer is not DC. The AC output is simply the input voltage divided by the turns ratio. So, if the input voltage is 120V, and the turns ratio is 5:1, then the output would be 24VAC. Now, if the transforner is followed by a rectifier, producing a DC output, then the output voltage depends on the type. For a half-wave rectifier, the DC output is 0.707 time the AC output. For a full-wave rectifier, the DC output will be 1.414 times the AC output. So, if we take our 24VAC transformer output, and feed it through a full-wave rectifier, the DC output would be 33.9VDC. If the rectifier output is smoothed by a filter capacitor, then the above is only true if the power supply is loaded. The half-wave rectifier output will drift up to the peak voltage (1.414 * AC) if it has no load.

Answer 2

The basic of this question is fairly simple. It is based on the number of turns ratio between one side of the transformer relative to the other side. In short, if I want to transform 120 volts down to 12 volts, I would have a ratio of 10 to 1 turns as a basic starting point.

In a transformer, there are typically two conductor circuits. One is the source side, and the other is the output side. Each circuit is typically a long strand of continuous wire wound around some kind of core. The core can be ferrite, wood, plastic for example. The number of windings around this core can be several thousand times. Parallel to this set of windings, the output side will also be similarly wound around a similar or same core.

When electricity passes through a conductor, it produces an electromagnetic field. This magnetic field can influence the electrons in nearby conductors and cause current to flow. This is referred to as induction. When current is induced from the primary to the secondary coil, electricity is present on the output of the secondary. The two circuits are considered isolated from each other. What voltages you get are dependent on the input voltage and the ratio of turns between the primary and secondary circuits. You can step up or step down, by increasing or decreasing the secondary number of turns respectively.

Further to this, current capabilities are dependant upon the cross section of the conductors on EACH side of the transformer and the overall number of turns in each coil relative to this cross section. This dictates the resistance or impedance of the coil, both by the natural impedance of the coil, the impedance of the conductor itself based on material. Copper versus gold versus aluminum for example.

Some very complex math goes with this to determine current capabilities on a given transformer. The difference of 1 amp at 10 volts versus 20 amps at 10 volts is dependant on knowing that information. However, as I said at the start, the basics are just the ratio of the number of turns of wire on the primary relative to the secondary side.

You can also have what is known as center tap Transformers, where a third or more conductors are attached at some point along the coil conductor. For example, if I placed a third wire roughly half way along the secondary coil's conductor, this would be in essence half the voltage output that would be found on the outputs original two wires, allowing me to have two equal output voltages which share a common. Or if I placed this wire one quarter the way along the coil, I could have two outputs, one at 3 quarters the total output, the other at one quarter the total output. Combinations of these allow you to have any number of output choices.

Answer 3

In any transformer, step up or step down voltage is a function of turns ratio. For instance, if the secondary has twice as many turns as the primary, the step up voltage is a factor of two.