Working principle of step down transformer pdf

Our present day electronics is heavily dependent on it. In this post, we will try to understand what is it, its working principle, equation, types, advantages and disadvantages. A Step Down Transformer is a device which converts high primary voltage to a low secondary voltage. In a Step Down Transformer, the primary winding of a coil has more turns than the secondary winding. Figure 1 below shows the winding representation of a typical Step-Down Transformer. Mutual induction between the windings is responsible for transmission action in a transformer.

The emf Electro Motive Force induced between the two windings is determined by the number of turns in primary and secondary winding respectively. This ratio is called as Turns Ratio. The voltage reduction capability of step down transformers depends on the turn ratio of the primary and secondary coil. As the number of windings in secondary coil is less as compared to the number of windings in primary coil, so the amount of flux linkage to the secondary coil of the transformer will also be less compared to the primary coil.

Accordingly, the emf induced will be less in the secondary coil. Due to this, the voltage reduces at the secondary winding compared to primary winding. The number of turns in secondary winding should always be less than the number of turns in the primary winding of the transformer i. As the number of turns will be less in secondary winding, so will be total induced emf and hence the output voltage in the secondary will also be less than the primary input voltage.

Then the voltage at the secondary [Vs] can be calculated by using the formula:. Hence, the voltage at the secondary winding of the transformer is 12V, which is less than that at the primary winding. Magnetic coupling.

You PDF is getting ready! Wait for some time. You have to wait 15 seconds. Download Timer JavaScript needs to be enabled in order to Books PDF. Home about us disclaimer privacy policy pages. Sunday, February 17, New. Working Principle of Transformer PDF I f you are finding for the working principle of transformer pdf then you are might at right place. Transformer is the device which is generally used for the step p or step down the voltage level as per the requirement. When primary winding is excited by an alternating voltage , it circulates an alternating current.

As the Flux is alternating according to faradays law of an electromagnetic induction , induced e. Here we provide two pdf of working principle of transformer try the both pdf and select the one which fulfill your criteria. PDF 1 - Transformer Working Principle PDF 2 - Transformer Fundamental pdf 2 is the fundamental related to transformer which also include the working principle of transformer and pdf 2 is much easier than the first one.

So first try to clear fundamental related to transformer and then also try the pdf 1. If you find the best pdf for working principle of transformer then comment which pdf you like so other can also get benifited.

Hope you find the working principle of transformer pdf. Whereas, a polarity is said to be a subtractive if the measured voltage between the high voltage and the low voltage terminals is lower than the supply voltage at the high voltage terminals. The Fig. The high voltage terminal H1 is connected to the low voltage terminal X1 by a cable.

The voltmeter is connected between H2 and X2. Suppose, a voltage of V is applied to the primary side. This connection is shown in Fig. Whereas in the power distribution substation, the three-phase voltage is again stepped down to 11 kV voltage through a three-phase distribution transformer. Whereas in the second approach, if one of the transformers becomes defective then the system can be given power by an open delta at a reduced capacity. In this case, the defective transformer is normally replaced by a new one.

A three-phase transformer with wye-delta connection is shown in Fig. The windings and their position to each other are usually marked by vector group. The vector group is used to identify the phase shift between the primary and secondary windings. The transformer vector group is labeled by capital and small letters plus numbers from 1 to 12 in a typical clock-like diagram. The capital letter indicates primary winding and small letter represents secondary winding. In the clock diagram, the minute hand represents the primary line to neutral line voltage, and its place is always in the The hour hand represents the secondary line to neutral voltage and its position in the clock changes based on the phase shift as shown in Fig.

There are four vector groups used in the three-phase transformer connection. Here, Y represents wye connection, D represents delta connection and z represents the zigzag connection. The connection diagrams for different combinations are shown in Figs. All these loads are operated with a constant magnitude of voltage. The secondary voltage of a transformer under operation changes due to voltage drop across the internal impedance and the load.

The voltage regulation of a transformer is used to identify the characteristic of the secondary side voltage changes under different loading conditions.

Phasor diagrams for different power factors are shown in Fig. The phasor diagram with a unity power factor is shown in Fig. The secondary coil resistance and reactance are 0. Calculate the voltage regulation if the secondary current of the transformer is 10 A at a 0. The resistance and reactance in the secondary winding are 0. Calculate the voltage regulation, when the secondary current is 6 A at a 0. Equation 2. The iron loss consists of the eddy current loss and the hysteresis loss. In the transformer, most of the flux transferred from the primary coil to the secondary coil through low reluctance iron path.

As a result, an emf is induced in the transformer core. A current will flow in that parts of the transformer. This current does not contribute in output of the transformer but dissipated as heat. This current is known as eddy current and the power loss due to this current is known as eddy current loss. Steel is a very good ferromagnetic material which is used for the core of a transformer. This ferromagnetic material contains number of domains in the structure and magnetized easily.

These domains are like small magnets located randomly in the structure. When an mmf is applied to the core then those domains change their position.

After removing mmf, most of the domains come back to their original position and remaining will be as it is. As a result, the substance is slightly permanently magnetized. An additional mmf is required to change the position of the remaining domains. Now that the magnetic flux density is usually constant, Eqs. Therefore, total losses of the transformer depend on the voltage and the current not on the power factor.

That is why the transformer rating is always represented in kVA instead of kW. In the transformer, copper losses occur due to the primary and the secondary resistances.

For a given power factor, the secondary current is varied with the variation of load. The denominator of Eq. From Eq. Consider that the power factor of the load is 0. The parameters of a transformer equivalent circuit can be determined by the open circuit and the short circuit tests. The components of the no-load current are used to determine the no-load circuit resistance and reactance.

In an open circuit test, the secondary side is considered to be open circuit, and the primary coil is connected to the source as shown in Fig. Then the wattmeter will measure the iron loss and small amount of copper loss.

The ammeter and voltmeter will measure the no-load current and the voltage, respectively. Since, the no-load current is very small, the copper losses can be neglected. Calculate the no-load circuit resistance and reactance. In this test, the supply voltage and the measuring instruments e. The primary voltage is adjusted until the current in the short-circuited winding is equal to the rated primary current.

Determine the i equivalent resistance, reactance and impedance referred to primary, ii equivalent resistance, reactance and impedance referred to secondary, and iii voltage regulation at unity power factor.

Practice problem 2. Find the i equivalent resistance, reactance and impedance referred to primary and ii equivalent resistance, reactance and impedance referred to secondary, and iii voltage regulation at a 0. This type of small rating transformer with a variable output is known as autotransformer. An autotransformer has one continuous winding that is common to both the primary and the secondary. Therefore, in an autotransformer, the primary and secondary windings are con- nected electrically.

The advantages of an autotransformer over a two-winding transformer include lower initial investment, lower leakage reactance, lower losses compared to conventional transformer and lower excitation current. An autotransformer with primary and secondary windings is shown in Fig.

From Fig. The voltages of the upper and lower parts of the coil are and V, respectively. Calculate the kVA rating of the autotransformer. Determine the kVA rating of the autotransformer. Therefore, an additional transformer is required to connect in parallel with the existing one.

This type of connection of a three-phase transformer is rarely used for large amount of power transmission. Neutral point is necessary for both primary and secondary sides in some cases. In balanced loads, this type of connection works satisfactorily and provides neutral to each side for grounding.