Pulse Transformer : Working and Applications

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Pulse Transformer : Working and Applications

An overview of the pulse transformer and its operation. This transformer is primarily designed to transfer electrical pulses, voltage pulses, or current pulses.

A pulse transformer is one of the most often used bespoke transformers in a variety of industries. Vacuum devices, in general, operate on high power pulse voltage, which is created by high power-based pulse transformers. These transformers feature a small construction and excellent repeatability. In most applications, it is anticipated to have a wide pulse width, a short rising time, and a high energy efficiency while transmitting.

These transformers are primarily used to carry heavy loads for electricity distribution. These are capable of broadcasting massive amounts of power when compared to a standard transmitter of comparable size, and they can operate at high frequencies. There are several reasons why these transformers are commonly used in various industrial settings. This article provides an overview of a pulse transformer and how it works.

Pulse Transformer Overview:

A pulse transformer is a type of transformer that is built and optimised to transmit voltage pulses between its two windings as well as to the associated load. These transformers are utilised for signal transmission in low-power control circuits and as critical components in high-power SMPS. The schematic of a pulse transformer is illustrated below.

Because these transformers handle currents and voltages in pulse form, they are commonly used as Isolating Transformers inside power electronic circuits to separate source and load. This type of transformer is utilised in radar, television, digital computers, and a variety of other applications. The pulse transformer's primary functions are as follows:

  • The amplitude of the voltage pulse can be adjusted.
  • The polarity of the pulse can be altered.
  • Different stages of a pulse amplifier can be connected together.
  • As an Isolation Transformer, it is used.

Pulse Transformer Design

A pulse transformer's design is primarily determined by criteria such as inductance, power rating, impedance, low to high voltage level, size, operating frequency, frequency response, winding capacitance, packing, and so on.

Transformer designers strive to eliminate parasitic factors such as winding capacitance and leakage inductance through winding layouts that improve coupling among transformer windings. This transformer may be constructed in a variety of sizes and forms by manufacturers such as Butler Winding by incorporating various standard type constructions.

Pulse transformers are compact in size and have fewer turns. As a result, the windings leakage inductance and interwinding capacitance of these transformers are low.

The pulse transformer has a high magnetising inductance because the cores are made of ferrites rather than wrapped strips of high permeability alloys. These transformers have high voltage insulation between two windings and toward the ground. Typically, these transformers handle the pulse signal; otherwise, the pulse is trained.

The performance of impulse transformers is primarily defined by their influence on the contour of the pulse input voltage or current. Small pulse transformers are commonly found in pulse generators, computers, and other electronic devices. Large pulse transformers are primarily utilised in radar systems to produce 50-100 MW of power at 200-300 kV in a matter of microseconds.

Types of Pulse Transformer

Power pulse transformers and signal pulse transformers are the two types of pulse transformers. Power pulse transformers are used to switch between power-level voltage ranges. These transformers are available in either 1-phase or 3-phase primary designs, with the primary design changing depending on the connected winding.

Signal transformers convey data from one type of circuit to another via electromagnetic induction. As a result, they are most commonly employed to increase or decrease the voltage from one face of a power transformer to another. The voltage change will be determined by the number of windings turns ratio while utilising these transformers.

Construction/Working

The pulse transformer's primary role is to provide a signal for a semiconductor device while also providing electrical isolation. A toroidal-shaped pulse transformer with two windings, main and secondary, is depicted below. The construction of a pulse transformer is depicted below.

Pulse Transformer : Working and Applications
  • Every winding has equivalent turns, hence any winding can function as a main or secondary winding.
  • The signal to the silicon-controlled rectifier can be delivered in the ratio of 1:1, otherwise in the ratio of 1:1:1 of the transformer.
  • The 3-winding-based transformer can supply a continuous signal to the SCR.
  • The second diagram shows the gate signal of the firing circuit as it passes through the pulse transformer.
  • The series resistor's role is to limit the holding current of the rectifier.

In this case, the diode 'D' is employed to avoid reversing gate current, and a 1:1:1 pulse transformer can be used to generate a continuous pulse to the SCR.

The three-winding pulse transformer is seen above. This transformer's design may be completed with excellent efficiency. To reduce the magnetising current, the inductance of the primary winding must be large. The direct current delivered across the transformer's primary winding might keep the core from being saturated.

The insulation between the two windings of the transformer can safeguard the transformer's winding. As a result, strong coupling between two windings is required. On a high frequency, the stray signal provides channel throughout inter-stage capacitance.

The output signal has a frequency influence. For high signal frequencies, the output signal shape and frequency are the same as the input signal. As a result, the output is exactly proportional to the assimilation of low signal frequency input.

Specifications

The pulse transformer specs primarily contain several characteristics linked with o/p response. These values will establish the maximum allowable pulse distortion.

-Pulse Amplitude

Apart from the meaningless spikes, the pulse amplitude is the maximum peak value of the signal.

-Rise Time (Tr)

The rise time is the amount of time it takes for the output signal to increase from 10% to 90% of its peak pulse amplitude during the initial attempt. In certain circumstances, it may be defined as the time taken by the output signal to respond to increasing from zero to pulse amplitude for the first time.

-Over Shoot

Overshoot is defined as an output signal that exceeds the peak amplitude.

-Pulse Width

The time period between the first and last instants when the instantaneous amplitude reaches 50% of the peak amplitude is known as pulse width or pulse duration.

-Droop

Droop, also known as tilt, is the displacement of the pulse amplitude during the level response.

-Fall time (Tf)

Fall time is defined as the time it takes via the output signal to lower the peak amplitude from 90% to 10% during the trailing edge response. It is sometimes referred to as decay time.

-Backswing

The backswing is the portion of the trailing edge that grows below the level of zero amplitude.

Pulse Transformer Uses/ Applications

The applications of pulse transformers include the following.

Pulse Generating Circuits

Analog Switching Applications

SCR

Power Electronics

Data Handling Circuits

Radar

Switching Transistors

Communication

Microwave Tube Circuits

Control Circuit for Firing Control

Cathode Ray Tube (CRO) Circuits

Radar Systems

Digital Electronics

The transmission line pulse transformer is mainly used in the applications of quick transmission of pulse signal & also in digital signal transmission.

Advantages & Disadvantages:

The advantages of pulse transformer include the following.

Small in Size

High Isolation Voltage

Inexpensive

Exterior Power Supply is not Required

It Operates at High Frequency.

It is Capable For Transmitting High Energy

Includes More Windings

Avoids Stray Currents

It Gives Insulation & Control

The disadvantages of pulse transformer include the following.

  • At low frequencies, the output waveforms diverge.
  • The DC supplies are distributed throughout the primary winding to reduce core saturation.
  • This Transformer Saturates at a Lower Frequency. As a result, it can only be used at maximum frequencies.
  • Because of the Magnetic Coupling, the signal is hazy.

Thus, this is only an overview of the pulse transformer and its operation. This transformer is primarily designed to transfer electrical pulses, voltage pulses, or current pulses. To preserve the outline, this transformer links the signal from the main to the secondary winding. As a result, the pulse transformer's performance may be evaluated by assessing the transformer's influence on the contour of the outside signal. As a result, its performance factor is mostly determined by the output signal's contour. Here's a question for you: what are the operational principles of a pulse transformer?

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