# Transformer primary and secondary voltage relationship

### Transformer Basic Operation

So far, we've observed simulations of transformers where the primary and secondary windings were of identical inductance, giving approximately equal voltage. 5. ISU EE. C.Y. Lee. The Basic Transformer. Source voltage is applied to the primary winding. The load is connected to the secondary winding. When you have completed this exercise, you will know the relationships between . transformers increase the voltage from the primary winding to the secondary.

There is usually significant to the numbering of the wires H1 versus H2, etc.

### Transformer primary and secondary voltage phase shift - Electrical Engineering Stack Exchange

Any device that could output more power than it took in would violate the Law of Energy Conservation in physics, namely that energy cannot be created or destroyed, only converted.

As with the first transformer example we looked at, power transfer efficiency is very good from the primary to the secondary sides of the device.

The practical significance of this is made more apparent when an alternative is considered: Figure below Motor generator illustrates the basic principle of the transformer. In such a machine, a motor is mechanically coupled to a generator, the generator designed to produce the desired levels of voltage and current at the rotating speed of the motor.

Transformers, on the other hand, are able to convert levels of AC voltage and current at very high efficiencies with no moving parts, making possible the widespread distribution and use of electric power we take for granted.

## Module 11.1

Notice how the primary inductor l1 has times more inductance than the secondary inductor H versus Hand that the measured voltage step-down ratio was 10 to 1. The winding with more inductance will have higher voltage and less current than the other.

Since the two inductors are wound around the same core material in the transformer for the most efficient magnetic coupling between the twothe parameters affecting inductance for the two coils are equal except for the number of turns in each coil. If we take another look at our inductance formula, we see that inductance is proportional to the square of the number of coil turns: The power losses that occur in a transformer are of three types; 1.

### Step-up and Step-down Transformers | Transformers | Electronics Textbook

These losses can also be called winding losses or I2R losses, because they can occur in windings made from metals other than copper. The losses become evident as heat, generated in the copper wire windings as they dissipate power due to the resistance of the wire. This formula is the reason copper losses are sometimes called I2R losses. To minimise the losses the resistance of the winding must be kept low, using wire of suitable cross sectional area and low resistivity.

Each time the alternating current reverses once each cycletiny "magnetic domains" within the core material are reversed.

These are physical changes within the core material and take up some energy. The amount of energy used depends on the "reluctance" of the core material; in large cores of power transformers where hysteresis loss maybe a problem it is largely overcome by using special low reluctance "grain oriented" steel as the core material. The inductance which produces this flux is also common to both windings and is called mutual inductance.

Figure 11 shows the flux produced by the currents in the primary and secondary windings of a transformer when source current is flowing in the primary winding.

## Step-up and Step-down Transformers

When a load resistance is connected to the secondary winding, the voltage induced into the secondary winding causes current to flow in the secondary winding. This current produces a flux field about the secondary shown as broken lines which is in opposition to the flux field about the primary Lenz's law.

Transformer Voltage and Turns Equation

Thus, the flux about the secondary cancels some of the flux about the primary. With less flux surrounding the primary, the counter emf is reduced and more current is drawn from the source.

The additional current in the primary generates more lines of flux, nearly reestablishing the original number of total flux lines.

The ampere-turn I X N is a measure of magneto motive force; it is defined as the magnetomotive force developed by one ampere of current flowing in a coil of one turn. The flux which exists in the core of a transformer surrounds both the primary and secondary windings.

Since the flux is the same for both windings, the ampere-turns in both the primary and secondary windings must be the same. By dividing both sides of the equation by IpN s, you obtain: Notice the equations show the current ratio to be the inverse of the turns ratio and the voltage ratio.

This means, a transformer having less turns in the secondary than in the primary would step down the voltage, but would step up the current.

A transformer has a 6: Find the current in the secondary if the current in the primary is milliamperes. The above example points out that although the voltage across the secondary is one-sixth the voltage across the primary, the current in the secondary is six times the current in the primary.

The above equations can be looked at from another point of view. The turns ratio indicates the amount by which the transformer increases or decreases the voltage applied to the primary. For example, if the secondary of a transformer has two times as many turns as the primary, the voltage induced into the secondary will be two times the voltage across the primary.