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What Is a Pulse Transformer?

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  • Originally Written By: N. Kalu
  • Revised By: C. Mitchell
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 20 August 2016
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Pulse transformers are a type of transformer that conducts and channels electrical currents in a pulse-like rhythm, rising and falling in waves with a constant amplitude. These pulsing waves are sometimes also called rectangular pulses because of their up-across-down shape when charted; they look much more like rectangles than the rolling hills of pulses from things like the human heart, for instance. Most of the transformers used to power things like city grids and standard electrical operations provide a more or less constant, or flat, current. Pulsing rectangular waves aren’t normally used in these scenarios, but there are several situations in which they are ideal, if not required. These include certain telecommunications circuits and digital logic situations, as well as some lighting situations, like camera flashes in complex photography equipment. Certain radar systems use them, too. There are usually two main signal types, namely signal and power. Each has a different pace, but generally has a very low tolerance for distributed capacitance and leakage inductance, as well as a high open-circuit inductance. Assembly for any type of pulse-based transformer is normally somewhat challenging, but assembly kits are available in many places for do-it-yourself experts or electronic hobbyists.

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Main Purpose

In general, transformers conduct electricity and filter signals to various outposts in a controlled, calculated way. Pulse-based transformers are no different, but they are distinguished by the way in which they regulate output. Rectangular electrical pulses have a quick fall and rise time, and are essential for applications that involve things like switching elements or required energy dumping. The smallest models are often very tiny, and are used in handheld electronics and many digital applications. Larger transformers are often essential to controlling flow in high-power semiconductors, among other things.

Signal Types

The size of the device and, by extension, the overall transformer design determines its function. There are two main types of pulse transformers: signal and power. Signal types, which are smaller transformers, handle relatively low power levels and deliver a series of pulses or pulse-like signals. They are used in situations where only a few volts are needed for a few microseconds, such as in telecommunication circuits and digital logic applications. Even some lighting applications use small pulse-generating transformers.

Power Pulse Models

The other main type of pulse-based transformer is the power pulse transformer. These devices require low coupling capacitances, which is critical to protecting the circuits on its primary side against highly powered transients from the electrical load. Power models also need high breakdown voltage and insulation resistance in order to run efficiently. They must have an adequate transient response in order to hold the rectangular shape of the pulse, because pulses with a less than optimal rise and fall time tends to induce switching loss in most power semiconductors.

Devices like controllers for camera flashes or other power-control circuits often use what's known as a medium power pulse transformer. Larger models are used in the electrical power distribution industry, where they facilitate interactions between the low voltage circuits and higher voltage gates found in power semiconductors. Some special versions are used in radar systems and other applications that require high power pulses.

High Voltage Transformers

There are also devices similar in function to the regular pulse-based transformer, and these are referred to as high voltage pulsing transformers. Unlike traditional transformers, the construction of these transformers are open and generally used in high voltage insulating oil. Typical pulse output voltages range from 100 to 500 kilovolts. Pulse lengths may vary from 0.25 microseconds to 50 microseconds.

Assembly Kits and Other Optimization Tools

Assemblies for these transformers include a full unit of tools and machinery that can optimize the performance of any transformer device. In addition to the pulse-generating transformer, the unit usually includes a current and a voltage monitor, bypass capacitors, and a heater transformer. A despiking network, klystron socket, and water cooling system are also part of the assembly. All of these components are part of a circuit that keeps pulse transmission constant and low in distortion. Specific measurements for each assembly, such as number of kilovolts, megawatts, and length of pulse in microseconds, are given on the company website or product label.

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